Brain histamine H1 receptor occupancy after oral administration of desloratadine and loratadine

Some histamine H1 receptor (H1R) antagonists induce adverse sedative reactions caused by blockade of histamine transmission in the brain. Desloratadine is a second-generation antihistamine for treatment of allergic disorders. Its binding to brain H1Rs, which is the basis of sedative property of antihistamines, has not been examined previously in the human brain by positron emission tomography (PET). We examined brain H1R binding potential ratio (BPR), H1R occupancy (H1RO), and subjective sleepiness after oral desloratadine administration in comparison to loratadine. Eight healthy male volunteers underwent PET imaging with [11C]-doxepin, a PET tracer for H1Rs, after a single oral administration of desloratadine (5 mg), loratadine (10 mg), or placebo in a double-blind crossover study. BPR and H1RO in the cerebral cortex were calculated, and plasma concentrations of loratadine and desloratadine were measured. Subjective sleepiness was quantified by the Line Analogue Rating Scale (LARS) and the Stanford Sleepiness Scale (SSS). BPR was significantly lower after loratadine administration than after placebo (0.504 ± 0.074 vs 0.584 ± 0.059 [mean ± SD], P < 0.05), but BPR after desloratadine administration was not significantly different from BPR after placebo (0.546 ± 0.084 vs 0.584 ± 0.059, P = 0.250). The plasma concentration of loratadine was negatively correlated with BPR in subjects receiving loratadine, but that of desloratadine was not correlated with BPR. Brain H1ROs after desloratadine and loratadine administration were 6.47 ± 10.5% and 13.8 ± 7.00%, respectively (P = 0.103). Subjective sleepiness did not significantly differ among subjects receiving the two antihistamines and placebo. At therapeutic doses, desloratadine did not bind significantly to brain H1Rs and did not induce any significant sedation.

Effect of taste masking technology on fast dissolving oral film: dissolution rate and bioavailability

Fast dissolving oral film is a stamp-style, drug-loaded polymer film with rapid disintegration and dissolution. This new kind of drug delivery system requires effective taste masking technology. Suspension intermediate and liposome intermediate were prepared, respectively, for the formulation of two kinds of fast dissolving oral films with the aim of studying the effect of taste masking technology on the bioavailability of oral films. Loratadine was selected as the model drug. The surface pH of the films was close to neutral, avoiding oral mucosal irritation or side effects. The thickness of a 2 cm × 2 cm suspension oral film containing 10 mg of loratadine was 100 μm. Electron microscope analysis showed that liposomes were spherical before and after re-dissolution, and drugs with obvious bitterness could be masked by the encapsulation of liposomes. Dissolution of the two films was superior to that of the commercial tablets. Rat pharmacokinetic experiments showed that the oral bioavailability of the suspension film was significantly higher than that of the commercial tablets, and the relative bioavailability of the suspension film was 175%. Liposomal film produced a certain amount of improvement in bioavailability, but lower than that of the suspension film.

When Hydromorphone Is Not Working, Try Loratadine: An Emergency Department Case of Loratadine as Abortive Therapy for Severe Pegfilgrastim-Induced Bone Pain

BACKGROUND

Intractable bone pain is a notorious adverse effect of granulocyte-colony stimulating factors (G-CSFs), such as pegfilgrastim and filgrastim, which are given to help prevent neutropenia in patients who are undergoing chemotherapy. G-CSF-induced bone pain is surprisingly common and often refractory to treatment with conventional analgesics.

CASE REPORT

This article describes an emergency department case of opiate and nonsteroidal anti-inflammatory drug-resistant pegfilgrastim-induced bone pain that was successfully alleviated with 10 mg of oral loratadine, allowing for discharge home. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case suggests that loratadine may be an easy to implement, safe, and effective therapy in the emergency department management of intractable bone pain caused by G-CSF use. Emergency physicians should be aware that loratadine may successfully relieve otherwise intractable G-CSF-induced bone pain and allow for discharge home.

[Determination of Desloratadine and Its Metabolite 3-OH Desloratadine in Human Plasma by LC-MS/MS]

OBJECTIVE

To develop a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of desloratadine and its metabolite 3-OH desloratadine in human plasma.

METHODS

24 healthy male volunteers received a single oral dose of 5 mg desloratadine tablets in a randomized crossover bioequivalence study with two preparations of tablets. Serial plasma samples were taken and analyzed by the LC-MS/MS method. The pharmacokinetic parameters of the two preparations were calculated and compared statistically to evaluate their bioequivalence using Winnonlin 6. 3.

RESULTS

The calibration curves of desloratadine and 3-OH desloratadine were both linear over the concentration range of 0. 050-6. 0 ng/mL, with intra-batch and inter-batch relative standard deviations less than 15%. The 90% confidence intervals (CIs) of peak concentration (Cmax) area under the curve (AUC)0t and AUC0-∞ of desloratadine and 3-OH desloratadine all resided within the bioequivalence limit 80%-125%. No significant difference in peak time (Tmax) was demonstrated between the two preparations.

CONCLUSION

The LC-MS/MS method can be used for simultaneous determination of desloratadine and 3-OH desloratadine in human plasma, which has been successfully applied-to a bioequivalence study.

Pharmacokinetics/Pharmacodynamics of Desloratadine and Fluoxetine in Healthy Volunteers

The authors assessed the potential for a pharmacokinetic/pharmacodynamic interaction between desloratadine and fluoxetine. This randomized, placebo-controlled, open-label study was conducted in 54 healthy volunteers. Subjects received 1 of 3 treatments: desloratadine 5 mg plus fluoxetine 20 mg, desloratadine 5 mg plus placebo, or fluoxetine 20 mg plus placebo. Serial electrocardiograms (ECGs) were performed at baseline and day 35. Treatment effects on C(max) and AUC were assessed. During coadministration of desloratadine with fluoxetine, the ratio of the mean log-transformed C(max) and AUC values for desloratadine following concomitant fluoxetine therapy revealed a small increase in C(max) values of 15% (90% confidence interval [CI], 95%-139%) but no increase for AUC values (90% CI, 82%-123%). Corresponding values for 3-OH desloratadine demonstrated small increases in mean log-transformed C(max) and AUC ratios: 17% (90% CI, 100%-136%) and 13% (90% CI, 96%-132%), respectively. Statistical evaluation of the ratio of the mean C(max) and AUC values for fluoxetine following concomitant desloratadine therapy revealed small decreases of 9% (90% CI, 72%-115%) and 11% (90% CI, 69%-113%), respectively. Corresponding values for norfluoxetine demonstrated modest increases in mean log-transformed C(max) and AUC ratios: 22% (90% CI, 100%-139%) and 18% (90% CI, 101%-136%), respectively. Coadministration of desloratadine with a potent inhibitor of CYP2D6 did not result in clinically relevant changes in its pharmacokinetic parameters. Desloratadine administration was not associated with clinically important changes in the pharmacokinetics of fluoxetine, a drug metabolized by CYP2D6. The most common adverse event in all groups was headache (65%). Desloratadine plus fluoxetine caused no significant changes in ECGs or ventricular rate.

Multiple-Dose Pharmacokinetics and Safety of Desloratadine in Subjects With Moderate Hepatic Impairment

Desloratadine, a nonsedating histamine H(1)-receptor antagonist, is metabolized to 3-hydroxy (3-OH) desloratadine. Impaired hepatic function could result in increased exposure to desloratadine. This study assessed possible differences in the pharmacokinetics and safety of desloratadine and 3-OH desloratadine in subjects (N = 21) with moderate hepatic dysfunction or normal liver function. Subjects were given desloratadine 5 mg once daily for 10 days and were assessed in several pharmacokinetic parameters. A similar degree of plasma protein binding to desloratadine and 3-OH desloratadine was observed in healthy volunteers and subjects with moderate hepatic impairment. All subjects with hepatic impairment were normal metabolizers. Three subjects with normal liver function, all African American, were identified as poor metabolizers. Exposure to desloratadine in the poor metabolizers was 2.6- to 6.5-fold greater than in other subjects with normal liver function. Eleven treatment-related adverse events, all mild to moderate in severity, were reported. Results suggest that subjects with moderate hepatic impairment experienced a greater increase in desloratadine exposure than subjects with normal liver function. Poor metabolizers had more exposure to desloratadine than normal metabolizers with or without hepatic impairment. Desloratadine administered at a daily dose of 5 mg was well tolerated.

[Comparative pharmacokinetics of antigrippin-maximum administered in capsules and powder for preparing solutions]

Comparative pharmacokinetics of anti-influenza drug composition Antigrippin-maximum administered in capsules and a powder for preparing solutions has been studied after single administraton in a group of 18 healthy volunteers. Both preparations [manufactured by the Antiviral Research and Production Corporation (St Petersbutg) contain 6 active components, including paracetamol, rimantadine, loratadine, ascorbic acid, calcium gluconate, and rutoside in equal amounts. The concentrations of unchanged paracetamol, rimantadine, and loratadine in the blood plasma were degtermined by HPLC with mass-spectrometric and UV detection. The pharmacokinetic parameters of allindicated active components exhibited no detectable distinctions, except for the time to attaining maximum concentration ofparacetamol and the value of the maximum concentration of loratadine.

Effects of silybinin, CYP3A4 and P-glycoprotein inhibitor in vitro, on the bioavailability of loratadine in rats

The effect of silybinin on the pharmacokinetics of orally and intravenously administered loratadine in rats was investigated. Pharmacokinetic parameters of loratadine were determined in rats following oral (4 mg x kg(-1)) and intravenous (1 mg x kg(-1)) administration to rats in the presence and absence of silybinin (0.3, 1.5 and 6 mg x kg(-1)). Compared to those animals in an oral control group (given loratadine alone), the area under the plasma concentration-time curve (AUC) and the peak plasma concentration (C(max)) of loratadine were increased significantly (P < 0.05 for 1.5 mg x kg(-1), P < 0.01 for 6 mg x kg(-1)) by 50.0-76.7% and 65.4-90.1%, respectively, by silybinin. Consequently, the absolute bioavailability of loratadine in the presence of silybinin (1.5 and 6 mg x kg(-1)) was 8.6-10.2%, which was significantly (1.5 mg x kg(-1), P < 0.05; 6 mg x kg(-1), P < 0.01) enhanced compared to that in oral control group (5.8%). Moreover, the relative bioavailability of loratadine was 1.50- to 1.77-fold greater than that in the control group. In contrast, silybinin had no effect on any pharmacokinetic parameters of loratadine given intravenously, implying that coadministration of silybinin could inhibit the cytochrome P450 (CYP) 3A4-mediated metabolism of loratadine, resulting in reducing gastrointestinal and hepatic first-pass metabolism, and the P-glycoprotein (P-gp) efflux pump in the small intestine. Silybinin significantly enhanced the oral bioavailability of loratadine, suggesting that concurrent use of silybinin and loratadine should be monitored closely for potential drug interactions.

Metabolism of loratadine and further characterization of its in vitro metabolites

The present study demonstrated that in addition to CYP3A4 and CYP2D6, the metabolism of loratadine is also catalyzed by CYP1A1, CYP2C19, and to a lesser extent by CYP1A2, CYP2B6, CYP2C8, CYP2C9 and CYP3A5. The biotransformation of loratadine was associated with the formation of desloratadine (DL) and further hydroxylation of both DL and the parent drug (loratadine). Based on the inhibition and correlation studies contribution of CYP2C19 in the formation of the major circulating metabolite DL seems to be minor. Reported clinical results suggest that the steady state mean (%CV) plasma Cmax and AUC(24hr) of loratadine were 4.73 ng/ml (119%) and 24.1 ng.hr/ml (157%), respectively, after dosing with 10 mg loratadine tablets for 10 days. High inter-subject variability in loratadine steady-state data is probably due to the phenotypical characteristics of CYP2D6, CYP2C19, and CYP3A4. The relative abundance of CYP3A4 in the human liver exceeds that of CYP2C19 and CYP2D6 and therefore the contribution of CYP3A4 in the metabolism of loratadine should be major (approximately 70%).

Comparison of the efficacy and safety of bilastine 20 mg vs desloratadine 5 mg in seasonal allergic rhinitis patients

BACKGROUND

Bilastine is a novel, nonsedating H(1)-antihistamine developed for symptomatic treatment of Allergic Rhinitis and Chronic Idiopathic Urticaria. The objective of this study was to compare the efficacy and safety of bilastine 20 mg vs placebo and desloratadine 5 mg in subjects with seasonal allergic rhinitis (SAR).

METHODS

This randomized, double blind, placebo-controlled, parallel-group multicentre study evaluated the effect of 2 weeks' treatment with bilastine 20 mg, desloratadine 5 mg or matched placebo once daily, in 12-70 years old symptomatic SAR patients. All subjects assessed the severity of nasal (obstruction, rhinorrhoea, itching, and sneezing) and nonnasal (ocular itching, tearing, ocular redness, itching of ears and/or palate) symptoms on a predetermined scale to provide a total symptom score (TSS), composed of nasal and nonnasal symptom scores (NSS and NNSS, respectively). The primary efficacy measure was the area under the curve (AUC) for the TSS over the entire treatment period.

RESULTS

Bilastine 20 mg significantly reduced the AUC of TSS to a greater degree from baseline compared to placebo (98.4 with bilastine vs 118.4 with placebo; P < 0.001), but not compared to desloratadine 5 mg (100.5). Bilastine 20 mg was not different from desloratadine 5 mg but significantly more effective than placebo in improving the NSS, NNSS, and rhinitis-associated discomfort scores (P < 0.05), and rhinoconjunctivitis quality of life questionnaire total (P < 0.005) and four out of seven individual domain (P < 0.05) scores. The incidence of treatment emergent adverse events was similar for bilastine (20.6%), desloratadine (19.8%), and placebo (18.8%).

CONCLUSION

Bilastine 20 mg once daily was efficacious, safe and not different from desloratadine 5 mg once daily in the treatment of SAR symptoms.

Disposition of loratadine in healthy volunteers

The absorption, metabolism and excretion of carbon-14-labeled loratadine (LOR, SCH 29851, Claritin) administered orally to healthy male volunteers were evaluated. Following a single oral 10-mg dose of [(14)C]LOR ( approximately 102 microCi), concentrations of LOR and desloratadine (DL; a pharmacologically active descarboethoxy metabolite of LOR) were determined in plasma. Metabolites in plasma, urine and feces were characterized using a liquid chromatography-mass spectrometry system (LC-MS) connected in line with a flow scintillation analyzer (FSA). Maximum plasma LOR and DL concentrations were achieved at 1.5 h and 1.6 h, respectively; thus, LOR was rapidly absorbed but also rapidly metabolized as indicated by these similar t(max) values. Metabolite profiles of plasma showed that LOR was extensively metabolized via descarboethoxylation, oxidation and glucuronidation. Major circulating metabolites included 3-hydroxy-desloratadine glucuonide (3-OH-DL-Glu), dihydroxy-DL-glucuronides, and several metabolites resulting from descarboethoxylation and oxidation of the piperidine ring. LOR was completely metabolized by 6 h post-dose. LOR-derived radiocarbon was excreted almost equally in the urine (41%) and feces (43%). About 13% of the dose was eliminated in the urine as 3-OH-DL-Glu. DL accounted for less than 2% of the dose recovered in the urine and only trace amounts of LOR were detected. 3-OH-DL was the major fecal metabolite ( approximately 17% of the dose). The combined amount of 5- and 6-hydroxy-DL contributed to an additional 10.7% of the dose in feces. Approximately 5.4% and 2.7% of the dose were excreted in the feces as unchanged drug and DL, respectively.

Metabolism and excretion of loratadine in male and female mice, rats and monkeys

The metabolism and excretion of loratadine (LOR), a long-acting non-sedating antihistamine, have been evaluated in male and female mice, rats and monkeys. Following a single (8 mg kg-1) oral administration of [14C]LOR, radioactivity was predominantly eliminated in the faeces. Profiling and characterization of metabolites in plasma, bile, urine and faeces from male and female mice, rats and monkeys showed LOR to be extensively metabolized with quantitative species and gender differences in the observed metabolites. In all species investigated, the primary biotransformation of LOR involved decarboethoxylation to form desloratadine (DL), subsequent oxidation (hydroxylation and N-oxidation) and glucuronidation. More than 50 metabolites were profiled using liquid chromatography-mass spectrometry (LC-MS) with in-line flow scintillation analysis (FSA) and characterized using LC-MSn techniques. The major circulating metabolite in male rats is a DL derivative in which the piperidine ring was aromatized and oxidized to pyridine-N-oxide. Much lower levels of the pyridine-N-oxide metabolite were observed in female rat plasma. In contrast, the relative amount of DL was notably higher in female than in male rats. The major circulating metabolite in either gender of mouse and male monkey is a glucuronide conjugate of an aliphatic hydroxylated LOR; in the female monkey, the major circulating metabolite is formed through oxidation of the pyridine moiety and subsequent glucuronidation. Qualitatively similar metabolic profiles were observed in the mouse, rat and monkey urine and bile, and the metabolites characterized resulted from biotransformation of LOR to DL, hydroxylation of DL and subsequent glucuronide conjugation. 5-Hydroxy-desloratadine was the major faecal metabolite across all three species irrespective of gender.

Disposition of desloratadine in healthy volunteers

The absorption, metabolism and excretion of desloratadine (DL, Clarinex) were characterized in six healthy male volunteers. Subjects received a single oral 10-mg dose of [(14)C]DL ( approximately 104 microCi). Blood, urine and feces were collected over 240 h. DL was well absorbed; drug-derived radioactivity was excreted in both urine (41%) and feces (47%). With the exception of a single subject, DL was extensively metabolized; the major biotransformation pathway consisted of hydroxylation at the 3 position of the pyridine ring and subsequent glucuronidation (3-OH-DL-glucuronide or M13). In five of the six subjects, DL was slowly eliminated (mean t((1/2)) = 19.5 h) and persisted in the plasma for 48-120 h post-dose. This is in contrast to a t((1/2)) of approximately 110 h and quantifiable plasma DL concentrations for the entire 240-h sampling period in one subject, who was identified phenotypically as a poor metabolizer of DL. This subject also exhibited correspondingly lower amounts of M13 in urine and 3-OH-DL (M40) in feces. Disposition of DL in this subject was characterized by slow absorption, slow metabolism and prolonged elimination. Further clinical studies confirmed the lack of safety issues associated with polymorphism of DL metabolism (Prenner et al. 2006, Expert Opinion on Drug Safety, 5: 211-223).

Influence of food on the oral bioavailability of rupatadine tablets in healthy volunteers: a single-dose, randomized, open-label, two-way crossover study

BACKGROUND

Rupatadine is an oral active antihistamine for the management of diseases with allergic inflammatory conditions, such as perennial and seasonal rhinitis and chronic idiopathic urticaria. Oral rupatadine has been approved for the treatment of allergic rhinitis and chronic urticaria in adults and adolescents in several European countries.

OBJECTIVE

The purpose of this study was to describe the effect of the concomitant intake of food on the pharmacokinetic profile and bioavailability of a single dose of rupatadine.

METHODS

This was a single-dose, randomized, open-label, 2-way crossover study in which healthy male and female volunteers received a single, 20-mg oral dose of rupatadine under fed and fasting conditions. Blood samples were collected and plasma concentrations of rupatadine and its active metabolites desloratadine and 3-hydroxydesloratadine were determined by liquid chromatography tandem mass spectrometry. Tolerability was based on the recording of adverse events (AEs), physical examinations, electrocardiograms, and laboratory tolerability tests immediately before each treatment period and at the final visit of the study.

RESULTS

Twenty-four volunteers (12 males; mean [SD] age, 25.4 [5.3] years [range, 18-34 years]; mean [SD] weight, 71.2 [4.3] kg [range, 64-77 kg]; 12 females; mean [SD] age, 26.8 [6.5] years [range, 18-38 years]; mean [SD] weight, 58.4 [6.8] kg, [range 50-69 kg]) were enrolled and randomized with equal distribution of sex. A significant increase in AUC from drug administration to the final quantifiable sample (AUC(0-t)) and AUC from drug administration to infinity (AUC(0-infinity)) values of rupatadine was seen under fed conditions without affecting C(max). The ratios (90% CI) of the mean log-transformed AUC(0-t) and AUC(0-infinity) for rupatadine revealed a significant increase in AUC(0-t) (ratio 131%; 90% CI, 111%-154%) and AUC(0-infinity) (ratio 133%; 90% CI, 113%-156%), whereas C(max) remained unaltered (ratio 97%; 90% CI, 80%-116%). Plasma concentration-time profiles of desloratadine and 3-hydroxydesloratadine were similar with and without food, and no differences were seen for AUC(0-t), AUC(0-infinity), or C(max). Seven (28%) subjects reported > or =1 AE. All AEs were mild, resolved spontaneously, and did not affect the outcome of the study.

CONCLUSIONS

The results of this study indicate that concomitant intake of food with a single 20-mg oral dose of rupatadine exhibits a significant increase in rupatadine bioavailability. Despite the absence of bioequivalence, the drug was well tolerated under fed and fasting conditions, and no major changes in severity and/or prevalence of AEs were reported.

Desloratadine dose selection in children aged 6 months to 2 years: comparison of population pharmacokinetics between children and adults

AIMS

The aim of this study was to identify the dose of desloratadine in children aged > or =6 months- < or =2 years that would yield a single-dose target exposure (AUC) comparable with that in adults taking 5 mg desloratadine as syrup.

METHODS

In a phase 1, single-dose, open-label, pharmacokinetic study in 58 children aged > or =6 months- <1 year and > or =1 year- < or =2 years were randomly assigned to desloratadine syrup 0.625 mg (1.25 ml) and 1.25 mg (2.5 ml), respectively. Because the volume of blood that could be collected from individual subjects was limited, a population pharmacokinetic approach was used to estimate the pharmacokinetics of desloratadine. Safety was assessed based on results of screening and postdose physical examinations, laboratory safety tests, vital signs, and adverse events.

RESULTS

The apparent clearance (CL/F) of desloratadine, population estimate (%CV), in children aged > or =6 months- <1 year was 27.8 l h(-1) (35) and corresponding values in children > or =1 year- < or =2 years was 35.5 l h(-1) (51), compared with 137 l h(-1) (58) for adults. The CL/F ratios (children to adults) indicated that doses of 1 mg for > or =6 months- <1 year and 1.25 mg for > or =1 year- < or =2 years would result in similar systemic exposure to that observed in adults receiving the recommended 5 mg dose. Desloratadine was well tolerated with no safety issues.

CONCLUSIONS

Doses of 1.0 and 1.25 mg in children aged > or =6 months- < or =2 years should result in an exposure to desloratadine similar to that of adults receiving doses of 5 mg.

Verapamil, but not probenecid, co-administration can convert desloratadine to a sedating antihistamine in mice

The possibility that non-sedating antihistamines could elicit sedation in mice due to drug-induced inhibition of brain PgP was evaluated by measuring the ability of desloratadine alone or in combination with verapamil to cause ataxia in mice. Also, the concentrations of desloratadine in plasma and in brain homogenates were measured by liquid chromatography-mass spectrometry. Relative to methylcellulose (control) treatment, verapamil plus desloratadine decreased rotarod performance of mice. Plasma concentrations of desloratadine appeared comparable in the mice treated with either desloratadine or verapamil plus desloratadine, however the rate of decline of desloratadine from brain tissue was slower in mice treated with verapamil plus desloratadine compared to mice treated with desloratadine only. These data suggest that inhibition of brain PgP can convert desloratadine to a sedating antihistamine in mice.

Determination of loratadine and its active metabolite in human plasma by high-performance liquid chromatography with mass spectrometry detection

A new sensitive and selective liquid chromatography coupled with mass spectrometry (LC/MS/MS) method for quantification of loratadine (LOR) and its active metabolite descarboethoxyloratadine (DSL) in human plasma was validated. After addition of the internal standard, metoclopramide, the human plasma samples (0.3 ml) were precipitated using acetonitrile (0.75 ml) and the centrifuged supernatants were partially evaporated under nitrogen at 37 degrees C at approximately 0.3 ml volume. The LOR, DSL and internal standard were separated on a reversed phase column (Zorbax SB-C18, 100 mmx3.0 mm i.d., 3.5 microm) under isocratic conditions using a mobile phase of an 8:92(v/v) mixture of acetonitrile and 0.4% (v/v) formic acid in water. The flow rate was 1 ml/min and the column temperature 45 degrees C. The detection of LOR, DSL and internal standard was in MRM mode using an ion trap mass spectrometer with electrospray positive ionisation. The ion transitions were monitored as follows: 383-->337 for LOR, 311-->(259+294+282) for DSL and 300-->226.8 for internal standard. Calibration curves were generated over the range of 0.52-52.3 ng/ml for both LOR and DSL with values for coefficient of determination greater than 0.994 by using a weighted (1/y) quadratic regression. The lower limits of quantification were established at 0.52 ng/ml LOR and DSL, respectively, with an accuracy and precision less than 20%. Both analytes demonstrated good short-term, long-term, post-preparative and freeze-thaw stability. Besides its simplicity, the sample treatment allows obtaining a very good recovery of both analytes, around 100%. The validated LC/MS/MS method has been applied to a pharmacokinetic study of loratadine tablets on healthy volunteers.

Review of desloratadine for the treatment of allergic rhinitis, chronic idiopathic urticaria and allergic inflammatory disorders

Desloratadine is a once-daily, non-sedating, non-impairing, selective histamine H1-receptor antagonist. It relieves the symptoms of seasonal allergic rhinitis (including nasal obstruction and congestion, and morning symptoms), perennial allergic rhinitis and chronic idiopathic urticaria by blocking multiple critical steps in the systemic allergic cascade and downregulating key allergy-induced inflammatory mediators. It also relieves asthma symptoms and decreases rescue medication use in patients with seasonal allergic rhinitis and comorbid asthma. Numerous clinical studies have demonstrated that desloratadine is safe, well tolerated and free of serious cardiac effects. Pharmacokinetic studies have demonstrated a low propensity for drug-drug or drug-food interactions. This review outlines the mechanism of action, efficacy and safety of desloratadine for the treatment of allergic inflammatory disorders.

The relative bioavailability of loratadine administered as a chewing gum formulation in healthy volunteers

OBJECTIVE

The aim of this study was to investigate the pharmacokinetics of loratadine and its active metabolite desloratadine after single-dose administration of loratadine as a conventional tablet, orally disintegrating tablet (smelt tablet) and a chewing gum formulation with and without the collection of saliva.

METHODS

Twelve healthy male volunteers participated in a four-period cross-over trial evaluating the effect of dosage forms on the pharmacokinetics of a single dose of loratadine. Loratadine was administered as two 10-mg conventional tablet, two 10-mg smelt tablet, a 30-mg portion of medicated chewing gum without collection of saliva and a 30-mg portion of medicated chewing gum with collection of saliva. Blood samples were taken at predefined sampling points 0-24 h after medication, and the plasma concentrations of loratadine and desloratadine were determined by high-performance liquid chromatography. Each study period was separated by a wash-out period of at least 7 days.

RESULTS

The mean dose-corrected area under the plasma concentration-time curve extrapolated to infinity AUC(0-infinity) for the chewing gum formulation was statistically significantly increased compared to the tablet formulation (geometric mean ratio: 2.68; 95%CI: 1.75-4.09). Desloratadine pharmacokinetic parameters from the chewing gum formulation were not statistically significantly different from the conventional tablet. Neither loratadine nor desloratadine pharmacokinetics of the smelt tablet formulation were statistically significantly different from the conventional tablet formulation. Plasma concentrations of desloratadine following the administration of loratadine as chewing gum with saliva collection were very low.

CONCLUSION

Our study showed that formulation of loratadine as a medicated chewing gum results in an almost threefold increase in relative bioavailability. This is most likely due to a bypass of first-pass metabolism as this study suggests that approximately 40% of the absorbed loratadine was absorbed via the oral mucosa.

Adult and paediatric poor metabolisers of desloratadine: an assessment of pharmacokinetics and safety

Antihistamines are widely used to treat allergic rhinitis (AR) and chronic idiopathic urticaria (CIU) in adults and children. Desloratadine is a once-daily oral antihistamine with a favourable sedation profile that is approved for the treatment of AR and CIU. Phenotypic polymorphism in the metabolism of desloratadine has been observed, such that some individuals have a decreased ability to form 3-hydroxydesloratadine, the major metabolite of desloratadine; such individuals are termed 'poor metabolisers of desloratadine'. This review describes the prevalence of poor metabolisers of desloratadine, quantifies the exposure to desloratadine in poor metabolisers and demonstrates that the increased exposure in poor metabolisers is independent of age when administered at age-appropriate doses. Furthermore, this review demonstrates that the increased exposure to desloratadine in poor metabolisers is not associated with any changes in the safety and tolerability profile of desloratadine, including cardiovascular safety.

Bioavailability of two oral formulations of loratadine 20 mg with concomitant ketoconazole: An open-label, randomized, two-period crossover comparison in healthy Mexican adult volunteers

BACKGROUND

Loratadine is a long-acting antihistamine with selective peripheral histamine H(1)-receptor antagonistic activity and fewer sedative effects compared with conventional antihistamines, and is widely used in Mexico. Although several generic formulations of loratadine are available in Mexico, based on a literature search, information concerning the bioavailability of each formulation in the Mexican population is not available.

OBJECTIVE

The aim of this study was to compare the bioavailability and tolerability of 2 oral formulations of loratadine 20 mg (two 10-mg tablets) used in Mexico: Sensibit (test formulation; Laboratorios Liomont S.A. de C.V., Mexico City, Mexico) and Clarityne (reference formulation; Schering-Plough S.A. de C.V., Mexico City, Mexico) in healthy volunteers.

METHODS

This open-label, randomized, 2-period crossover study was conducted at Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, Mexico. Eligible subjects were healthy male Mexican volunteers aged > or=18 years. Subjects were randomly assigned to receive a single 20-mg dose (two 10-mg tablets) of the test or reference formulation, followed by a 2-week washout period, followed by the same dose of the alternate formulation. A 400-mg dose of ketoconazole (2 doses in 24 hours) was administered to each subject before the administration of each formulation, and a 200-mg dose of ketoconazole was given together with each formulation (ie, a total of 600 mg of ketoconazole was administered). Doses were administered after a 12-hour overnight fast. For analysis of pharmacokinetic properties, including C(maX), AUC(0-t), and AUC(0-infinity), blood samples were drawn at 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 2.5, 3, 5, 8, 12, 16, and 22 hours after dosing. The formulations were considered bioequivalent if the geometric mean ratios of C(maX) and AUC were within the predetermined equivalence range of 80% to 125%. Tolerability was assessed by monitoring vital signs and subject interview regarding the potential presence of adverse events (AEs).

RESULTS

Thirty-two subjects were enrolled in the study (mean age, 22 years [range, 18-28 years]; mean weight, 68.9 kg [range, 58-79 kg]; mean height, 170.8 cm [range, 158-183 cm]). Sixteen subjects received the test formulation first. No period or sequence effect was observed. The 90% CIs for the corresponding ratios of CmaX, AUC(0-t), and AUC(0-infinity) were 81.43% to 106.01%, 83.12% to 100.23%, and 84.06% to 101.10% (all, P < 0.05), meeting the predetermined criteria for bioequivalence. Similar results were found for data without a logarithmic transformation. No AEs were reported throughout the study.

CONCLUSIONS

In this small study in healthy Mexican volunteers, a single, 20-mg dose of the test formulation of loratadine was found to be bioequivalent to that of the reference formulation based on the rate and extent of absorption when concomitantly administered with ketoconazole. Both formulations were well tolerated.

Simultaneous determination of loratadine and pseudoephedrine sulfate in human plasma by liquid chromatography–electrospray mass spectrometry for pharmacokinetic studies

To support the pharmacokinetic and bioavailability study of an extended-release loratadine (LOR)/pseudoephedrine sulfate (PES) tablet, a high performance liquid chromatographic-electrospray ionisation-mass spectrometric method (LC-MS) was developed for the simultaneous determination of LOR and PES in human plasma. Diazepam (DP) and phenylpropanolamine (PPA) were used as internal standards for LOR and PES, respectively. Analytes were extracted from alkalized human plasma by liquid/liquid extraction using ethyl ether. Chromatographic separation was performed on an ODS column at flow rate of 0.2 ml/min. The total chromatographic run time was 10.5 min with the retention time of 7.1 min and 6.2 min for LOR and DP, respectively, and 2.2 min for both of PES and PPA. The LOQ was 10 pg/ml and 50 pg/ml for LOR and PES, respectively. The method is accurate and precise enough for its intended purpose.

Suppression of the histamine-induced wheal and flare response by fexofenadine HCl 60 mg twice daily, loratadine 10 mg once daily and placebo in healthy Japanese volunteers

BACKGROUND

The effects of the selective H1-receptor antagonist fexofenadine have been widely demonstrated in Western populations; however, to date, limited data comparing the effects of fexofenadine with other antihistamines have been reported in Japanese subjects.

OBJECTIVE

To investigate the effect of fexofenadine and loratadine on the histamine-induced cutaneous wheal and flare response in healthy Japanese volunteers.

METHODS

Eighteen healthy male and female Japanese volunteers aged 20-53 years were randomized to receive fexofenadine HCl 60 mg twice daily, loratadine 10 mg once daily or placebo in a 1-day, three-period, double-blind, crossover study. For each treatment, the wheal and flare response to 100 mg/mL histamine was assessed at baseline and at 1, 1.5, 2, 2.5, 3, 3.5, 4, 8, 12 and 24 hours post-dose. Blood samples were taken for pharmacokinetic analysis.

RESULTS

Fexofenadine produced significantly greater percentage suppression of the overall wheal response compared with placebo and loratadine (43.1% versus 10.0% and 15.2%, respectively; p < 0.001). Similarly, fexofenadine significantly suppressed the overall flare response compared with placebo and loratadine (43.0% versus 3.5% and -8.9%, respectively; p < 0.01). Loratadine was statistically no different from placebo in terms of both overall wheal and flare suppression. Area under the curve analysis for wheal and flare reduction (0-12 hours post-dose) confirmed these findings. For wheal inhibition, fexofenadine had a significantly faster onset of action (defined as time to > or = 35% inhibition) compared with placebo (p < 0.001) and loratadine (p < 0.01); for flare, fexofenadine had a significantly faster onset of action than loratadine (p < 0.01). Mean maximum inhibition (the mean of the greatest inhibition achieved from baseline for each treatment) for wheal was achieved significantly faster with fexofenadine than loratadine (p < 0.01), and fexofenadine had a significantly longer duration of effect on suppressing wheal and flare compared with placebo and loratadine (p < 0.05 for all). The antihistamine effects of fexofenadine correlated significantly with its Cmax, while loratadine activity did not correlate significantly with its plasma levels.

CONCLUSIONS

Fexofenadine is a potent suppressor of the histamine-induced wheal and flare response in healthy Japanese volunteers. These results support findings in Caucasian subjects, and confirm that fexofenadine has greater antihistaminergic activity than loratadine in this human model.

Classification of loratadine based on the biopharmaceutics drug classification concept and possible in vitro-in vivo correlation

Loratadine was studied both in vitro and in vivo (in healthy humans) to classify it according to the Biopharmaceutics Classification System (BCS) in order to gain more understanding of the reasons for its highly variable nature with respect to plasma time profiles, and to determine the most appropriate dissolution test conditions for in vitro assessment of the release profile of the drug from solid dose forms. Based on the solubility of loratadine determined under various pH conditions and its permeability through Caco-2 monolayers, loratadine was classified as a Class II drug. Plasma profiles were predicted by convolution analysis using dissolution profiles obtained under various pH and hydrodynamic conditions as the input function and plasma time data obtained from a syrup formulation as the weighting function. The predicted profiles based on dissolution studies done at gastric pH values were in reasonable agreement with the mean bio-data suggesting dissolution testing should be done at gastric pH values. However, the bio-data were highly variable and it is suggested this may be due, at least in part, to high individual gastric pH variability and dissolution occurring in the intestine on some occasions, and therefore, dissolution testing should also be done in simulated intestinal fluid.

Co-administration of ketoconazole with H1-antagonists ebastine and loratadine in healthy subjects: pharmacokinetic and pharmacodynamic effects

AIMS

Two studies were conducted to evaluate the effects of coadministration of ketoconazole with two nonsedating antihistamines, ebastine and loratadine, on the QTc interval and on the pharmacokinetics of the antihistamines.

METHODS

In both studies healthy male subjects (55 in one study and 62 in the other) were assigned to receive 5 days of antihistamine (ebastine 20 mg qd in one study, and loratadine 10 mg qd in the other) or placebo alone using a predetermined randomization schedule, followed by 8 days of concomitant ketoconazole 450 mg qd/antihistamine or ketoconazole 400 mg qd/placebo. Serial ECGs and blood sampling for drug analysis were performed at baseline and on study days 5 (at the end of monotherapy) and 13 (at the end of combination therapy). QT intervals were corrected for heart rate using the formula QTc = QT/RR(alpha) with special emphasis on individualized alpha values derived from each subject's own QT/RR relationship at baseline.

RESULTS

No significant changes in QTc interval from baseline were observed after 5 days administration of ebastine, loratadine or placebo. Ketoconazole/placebo increased the mean QTc (95% CI) by 6.96 (3.31-10.62) ms in the ebastine study and by 7.52 (4.15-10.89) ms in the loratadine study. Mean QTc was statistically significantly increased during both ebastine/ketoconazole administration (12.21 ms; 7.39-17.03 ms) and loratadine/ketoconazole administration (10.68 ms; 6.15-15.21 ms) but these changes were not statistically significantly different from the increases seen with placebo/ketoconazole (6.96 ms; 3.31-10.62 ms), P = 0.08 ebastine study, (7.52 ms; 4.15-10.89 ms), P = 0.26 loratadine study). After the addition of ketoconazole, the mean area under the plasma concentration-time curve (AUC) for ebastine increased by 42.5 fold, and that of its metabolite carebastine by 1.4 fold. The mean AUC for loratadine increased by 4.5 fold and that of its metabolite desloratadine by 1.9 fold following administration of ketoconazole. No subjects were withdrawn because of ECG changes or drug-related adverse events.

CONCLUSIONS

Ketoconazole altered the pharmacokinetic profiles of both ebastine and loratadine although the effect was greater for the former drug. The coadministration of ebastine with ketoconazole resulted in a non significant mean increase of 5.25 ms (-0.65 to 11.15 ms) over ketoconazole with placebo (6.96 ms) while ketoconazole plus loratadine resulted in a nonsignificant mean increase of 3.16 ms (-2.73 to 8.68 ms) over ketoconazole plus placebo (7.52 ms). Changes in uncorrected QT intervals for both antihistamines were not statistically different from those observed with ketoconazole alone. The greater effect of ketoconazole on the pharmacokinetics of ebastine was not accompanied by a correspondingly greater pharmacodynamic effect on cardiac repolarization.

A Review of the Evidence from Comparative Studies of Levocetirizine and Desloratadine for the Symptoms of Allergic Rhinitis

BACKGROUND

Levocetirizine and desloratadine are newer antihistamines indicated for the treatment of allergic rhinitis and chronic idiopathic urticaria.

OBJECTIVE

This article discusses the pharmacokinetics and pharmacodynamics of levocetirizine and desloratadine and reviews studies that have directly compared the effects of these 2 drugs in allergic rhinitis and urticaria.

METHODS

Relevant articles were identified through a search of MEDLINE from 1999 through 2004 using the main search terms levocetirizine and desloratadine.

RESULTS

Levocetirizine is absorbed rapidly and reaches a steady-state plasma concentration more quickly than does desloratadine. It is also metabolized to a lesser extent than desloratadine, has a lower V(d), and has higher specificity for histamine(1) receptors. Eight well-controlled trials were identified that directly compared the effects of levocetirizine and desloratadine in the skin and nose of healthy individuals and patients with allergic rhinitis. Drug activity was measured in terms of wheal, flare, and itch reactions; nasal symptoms or symptom scores; increases in concentrations of inflammatory markers; or facial thermography. In most of these trials, levocetirizine had a faster onset and greater consistency of effect than desloratadine. The differences in the pharmacokinetic and pharmacodynamic profiles of the 2 drugs may partially explain these clinical findings.

CONCLUSIONS

Levocetirizine may be preferred to desloratadine as a treatment option for allergic rhinitis because of its faster onset of action and greater consistency of effect. Although comparative studies in chronic idiopathic urticaria are not available, data from histamine-induced wheal and flare studies in healthy volunteers suggest that levocetirizine may be more effective in preventing itching than desloratadine.

[Study on determination of desloratadine in human serum and its pharmacokinetics by HPLC/MS]

OBJECTIVE

To study the determination of desloratadine in human serum and its pharmacokinetics in healthy volunteers.

METHODS

A single oral dose of 10 mg desloratadine was given to 18 healthy volunteers. The serum concentrations of desloratadine were determined by HPLC-MS assay. The pharmacokinetics parameters of desloratadine tablets were calculated with program 3P97.

RESULT

The main pharmacokinetics parameters of desloratadine tablets were as followsút(max)(1.611 +/-0.366)h, C(max) (4.455+/-1.990)microg x L(-1), AUC(0-t) (58.50+/-21.34)microg x L(-1) x h(-1), AUC(0-infinity) (60.59+/-22.32)microg x L(-1) x h(-1), t(1/2(ke)) (20.303+/-5.833)h, Ke (0.0372+/-0.0116)h(-1) and CL(0.1838+/-0.0563)L x h(-1).

CONCLUSION

Desloratadine tablet is absorbed quicker in the 18 healthy volunteers than the reports and its peak blood concentration reached at 1.5 h after oral administration with t(1/2) 20 h.

EFFECT OFCYP2D6*10ALLELE ON THE PHARMACOKINETICS OF LORATADINE IN CHINESE SUBJECTS

Loratadine is known to be a substrate for both CYP3A4 and CYP2D6 based on a previous in vitro study. In view of the large interindividual variability in loratadine pharmacokinetics and the greater genetically determined variability of CYP2D6 activity than of CYP3A4 in vivo, we hypothesized that CYP2D6 polymorphisms may contribute to the pharmacokinetic variability of loratadine. The purpose of this study was to evaluate the effect of CYP2D6 genotype (specifically the CYP2D6*10 allele) on the pharmacokinetics of loratadine in Chinese subjects. Three groups of healthy male Chinese subjects were enrolled: group I, homozygous CYP2D6*1 (*1/*1, n=4); group II, heterozygous CYP2D6*10 (*1/*10 or *2/*10, n=6); and group III, homozygous CYP2D6*10 (*10/*10, n=7) carriers. Each subject received a single oral dose of 20 mg of loratadine under fasting conditions. Multiple blood samples were collected over 48 h, and the plasma concentrations of loratadine and its metabolite desloratadine were determined by high-performance liquid chromatography. In comparing homozygous CYP2D6*10 (group III) to heterozygous CYP2D6*10 (group II) to homozygous CYP2D6*1 (group I) subjects, loratadine oral clearance values were 7.17+/- 2.54 versus 11.06+/-1.70 versus 14.59+/-2.43 l/h/kg, respectively [one-way analysis of variance (ANOVA), p<0.01], and the corresponding metabolic ratios [area under the plasma concentration-time curve (AUC)(desloratadine)/AUC(loratadine)] were 1.55+/-0.73 versus 2.47+/- 0.46 versus 3.32+/- 0.49, respectively (one-way ANOVA, p<0.05), indicating a gene-dose effect. The results demonstrated that CYP2D6 polymorphism prevalent in the Chinese population significantly affected loratadine pharmacokinetics.

Development and bioadhesive properties of chitosan-ethylcellulose microspheres for nasal delivery

Loratadine-loaded microspheres were prepared by spray-drying of dispersions, emulsions and suspensions differing in polymeric composition and solvents used. Conventional microspheres were obtained by spray-drying of dispersions composed of chitosan (CM) as only polymer, while composed microspheres were obtained by spray-drying of two-phase systems composed of chitosan and ethylcellulose (EC). Microspheres differed in EC/CM weight ratio (0:1, 1:2 and 1:3) and in loratadine/polymers weight ratio (1:6 and 1:8). The entrapment efficiencies were between 67.9 and 86.1%; less loratadine was entrapped as polymer/drug ratio decreased. In comparison to one-phase systems composed of CM as only polymer, spray-drying of two-phase systems composed of both, CM and EC resulted in improved loratadine entrapment (80.1-86.1%). All microspheres were positively charged, indicating the presence of chitosan at the surface, regardless of the drug content and the type of spray-dried system. The highest zeta-potential was measured for loratadine-free conventional microspheres, consisting of chitosan only (32.7+/-1.3 mV). Tensile studies showed that both, EC/CM ratio and the type of spray-dried system influenced the bioadhesive properties of the microspheres in a way that the microspheres with higher chitosan content were more bioadhesive and microspheres prepared from suspensions were more bioadhesive than those prepared from emulsions, regardless of the same polymeric composition. The results suggested that the spray-drying method is useful to produce bioadhesive loratadine-loaded microspheres.

Comparison of pharmacokinetics and metabolism of desloratadine, fexofenadine, levocetirizine and mizolastine in humans

Abstract Absorption, distribution, metabolism and excretion of desloratadine, fexofenadine, levocetirizine, and mizolastine in humans have been compared. The time required to reach peak plasma levels (tmax) is shortest for levocetirizine (0.9 h) and longest for desloratadine (> or =3 h). Steady-state plasma levels are attained after about 6 days for desloratadine, 3 days for fexofenadine, 2-3 days for mizolastine and by the second day for levocetirizine. The apparent volume of distribution is limited for levocetirizine (0.4 L/kg) and mizolastine (1-1.2 L/kg), larger for fexofenadine (5.4-5.8 L/kg) and particularly large for desloratadine (approximately 49 l/kg). Fexofenadine and levocetirizine appear to be very poorly metabolized (approximately 5 and 14% of the total oral dose, respectively). Desloratadine and mizolastine are extensively metabolized. After administration of 14C-levocetirizine to healthy volunteers, 85 and 13% of the radioactivity are recovered in urine and faeces, respectively. In contrast, faeces are the preferential route of excretion for 14C-fexofenadine (80% vs. 11% of the radioactive dose in urine). The corresponding values are 41% (urine) and 47% (faeces) for 14C-desloratadine, 84-95% (faeces) and 8-15% (urine) for 14C-mizolastine. The absolute bioavailability is 50-65% for mizolastine; it is high for levocetirizine as the percentage of the drug eliminated unchanged in the 48 h urine is 77% of the oral dose; the estimation for fexofenadine is at least 33%; no estimation was found for desloratadine. Fexofenadine is a P-glycoprotein (P-gp) substrate and P-gp is certainly involved both in the poor brain penetration by the compound and, at least partially, in a number of observed drug interactions. An interaction of desloratadine with P-gp has been suggested in mice, whereas the information on mizolastine is very poor. The fact that levocetirizine is a substrate of P-gp, although weak in an in vitro model, could contribute to prevent drug penetration into the brain, whereas it is unlikely to be of any clinical relevance for P-gp-mediated drug interactions.

Cetirizine and loratadine-based antihistamines with 5-lipoxygenase inhibitory activity

A series of compounds possessing both H(1) histamine receptor antagonist and 5-lipoxygenase (5-LO) inhibitory activities was synthesized. The H(1)-binding scaffolds of cetirizine, efletirizine, and loratadine were linked to a lipophilic N-hydroxyurea, the 5-LO inhibiting moiety of zileuton. Both activities were observed in vivo, as was increased CYP3A4 inhibition compared to their respective single-function drugs. Selected analogs in the series were shown to be orally active in guinea pig models.

High-performance liquid chromatographic method for the bioequivalence evaluation of desloratadine fumarate tablets in dogs

A simple HPLC method was developed for the determination of desloratadine in dog plasma and was used for evaluating the bioequivalence of desloratadine fumarate tablets and desloratadine tablets in dogs. Chromatographic separation was performed on a Hypersil CN column (150 mm x 5.0 mm, 5 microm) using a mixture of methanol, acetonitrile and phosphate buffer (pH 5.5; 0.01 mol/l) (35:35:30, v/v/v) as mobile phase delivered at a flow rate of 0.8 ml/min. The detection was set at 241 nm. The limit of quantitation was 5.0 ng/ml. The calibration range was from 5.0 to 800.0 ng/ml. Inter- and intra-day precision ranged from 1.8 to 3.8% and from 2.2 to 9.0%, respectively. The recovery of desloratadine from dog plasma ranged from 78.8 to 82.0%. The developed method was applied to the bioequivalence studies of desloratadine fumarate tablets (test preparation) and desloratadine tablets (reference preparation) in five dogs. Pharmacokinetic parameters t(max), C(max), AUC(0-t), AUC(0- infinity ), t(1/2) were determined from plasma concentration-time profiles of both preparations. The analysis of variance (ANOVA) did not show any significant difference between the two preparations and 90% confidence intervals fell within the acceptable range for bioequivalence. Based on these statistical inferences it was concluded that the two preparations exhibited comparable pharmacokinetic profiles and that desloratadine fumarate tablets was bioequivalent to desloratadine tablets.

A validated HPLC-ESI-MS method for the determination of loratadine in human plasma and its application to pharmacokinetic studies

A liquid chromatographic-mass spectrometric (LC-MS) assay was developed and validated for the determination of loratadine in human plasma using reversed-phase HPLC combined with electrospray ionization (ESI) mass spectrometry. The analysis involved a simple liquid-liquid extraction. The organic extract was then evaporated and the residue was reconstituted in mobile phase. The reconstituted solution was injected into an HPLC system and was subjected to reverse-phase HPLC on a 5-microm ODS-3 column at a flow-rate of 0.2 ml/min. The mobile phase comprised of acetonitrile-ammonium acetate (pH 4.0; 0.02 M, using formic acid to adjust) using gradient elution. Loratadine was detected in the single ion monitoring (SIM) mode. Standard curves were linear over the concentration range of 0.2-100 ng/ml. The mean predicted concentrations of the quality control (QC) samples deviated by less than 10% from the corresponding nominal values; the intra-assay and inter-assay precision of the assay were within 12% relative standard deviation. The extraction recovery of loratadine was more than 80%. The validated assay was applied to a pharmacokinetic study of loratadine in human plasma following the administration of a single loratadine tablet (40 mg).

Pharmacokinetics and bioequivalence study of a generic desloratadine tablet formulation in healthy male volunteers

The pharmacokinetic profiles and relative bioavailability of desloratadine (CAS 100643-71-8, Denosin as test and another commercially available preparation as reference) tablets from two different pharmaceutical manufacturers were carried out. A single oral dose (10 mg/2 tablets) of desloratadine was administered to 8 healthy young Chinese males in a completely double-blind cross-over design with a two-week washout period between each dose. Plasma samples were obtained before and at various appropriate intervals after dosing up to 120 h. The plasma concentrations were then analyzed by a liquid chromatography/tandem mass spectrometric (LC/MS/MS) method. The limit of quantitation of this LC/MS/MS method was 0.05 ng/mL. The coefficients of variation of the within-day and between-day calibration curves (n = 6) range from 0.05 ng/mL to 10 ng/mL and were less than 10%. The accuracy of this method was verified. Values for the area under the plasma concentration-time curve (AUC), peak concentration (Cmax), time to peak concentration (Tmax), elimination rate constant, half-life, oral clearance were estimated and compared for each preparation. By ANOVA, 90% confidence interval, Mann-Whitney test, and paired t-test, the two desloratadine products can be considered bioequivalent for both the extent and the rate of absorption.

Comparative efficacy of wheal-and-flare suppression among various non-sedating antihistamines and the pharmacologic insights to their efficacy

BACKGROUND AND OBJECTIVE

Non-sedating antihistamines (loratadine, fexofenadine, and cetirizine) have been widely used in Thailand. This study examined the time-of-onset and compared the 95% inhibitory effect of these agents on histamine-induced cutaneous reaction so as to understand the diversity of their efficacy.

PATIENTS AND METHOD

Thirty-one atopic patients were randomized into 4 treatment groups, placebo (n = 7), loratadine (n = 8), fexofenadine (n = 8), and cetirizine (n = 8). They were pricked with histamine every 30 min for 4 hrs. The percentage change of the wheal/flare area was calculated.

RESULTS

All active treatments showed wheal suppression superior to placebo after 210 min for loratadine (P = 0.04); 90 min for fexofenadine (P = 0.009); and 60 min for cetirizine (P = 0.02), while flare suppression was significantly marked after 150 min (P = 0.0008) for loratadine; 90 min for fexofenadine (P = 0.0001), and 60 min for cetirizine (P = 0.006). All drugs except loratadine demonstrated a 95% suppression of wheal superior to the placebo (P = 0.001 for fexofenadine; P = 0.0001 for cetirizine). Only fexofenadine exhibited a 95% suppression of flare statistically superior to placebo (P = 0.02). Discrepancies among the effects of these 3 antihistamines were also detected.

DISCUSSION AND CONCLUSION

All antihistamines tested repressed the wheal-and-flare area superbly over the placebo within 4 hours. Cetirizine exerted the fastest onset, and it also appeared to be the most efficacious inhibitor. The heterogeneity of their efficacy probably stems from their diverse physicochemical properties, which have also been discussed.

Desloratadine: an update of its efficacy in the management of allergic disorders

Desloratadine (Clarinex, Neoclarityn, Aerius, Azomyr, Opulis, Allex), the principal metabolite of loratadine, is itself an orally active, nonsedating, peripheral histamine H(1)-receptor antagonist. It is indicated in the US and Europe for the treatment of seasonal allergic rhinitis (SAR), perennial allergic rhinitis (PAR) and chronic idiopathic urticaria (CIU). It has a rapid onset of effect, efficacy throughout a 24-hour dosage interval, and sustained efficacy in these allergic conditions, as demonstrated in placebo-controlled trials of up to 6 weeks' duration in adult and adolescent patients. At present, there are no published direct comparisons of desloratadine and other H(1)-antihistamines; however, the principal, potential clinical advantages of desloratadine over late-generation H(1)-antihistamines are the drug's decongestant activity, which has been corroborated in several studies of patients with allergic rhinitis, and its anti-inflammatory effects. Indeed, the decongestant activity of desloratadine did not differ from that of pseudoephedrine in a trial in patients with SAR, and in patients with SAR and coexisting asthma, desloratadine reduced asthma symptoms and beta(2)-agonist use, and improved forced expiratory flow in 1 second. However, these issues warrant further study. Desloratadine is generally well tolerated. The overall incidence of adverse events in adults, adolescents and children was not significantly different to that with placebo, and similar proportions of desloratadine or placebo recipients reported events such as pharyngitis, dry mouth, myalgia, somnolence, dysmenorrhoea or fatigue. Desloratadine does not cause sedation or prolong the corrected QT (QTc) interval, can be administered without regard to concurrent intake of food and grapefruit juice, and appears to have negligible potential for drug interactions mediated by several metabolic systems.

CONCLUSION

Although comparative studies with second-generation and other recently developed H(1)-antihistamines are needed to define the drug's clinical profile more clearly, desloratadine can be expected to claim a prominent place in the management of allergic disorders in general, and in the amelioration of specific symptoms of allergy (e.g. nasal congestion) in patients with such disorders.

Onset of action for the relief of allergic rhinitis symptoms with second-generation antihistamines

Onset of action for relief of allergic rhinitis symptoms is of clinical significance to both the physician and the patient. Using either subjective or objective methods, the onset of action after a single, oral dose of an antihistamine can be measured. Multicenter studies, outdoor studies, and pollen challenge systems have been used to measure the onset of action. A literature search from 1985 to May 2002 was performed. All published, randomized, placebo-controlled clinical studies pertaining to the onset of action for relief of allergic rhinitis symptoms after a single, oral dose of a second-generation antihistamine (not combined with a decongestant) including cetirizine, desloratadine, fexofenadine, and loratadine, were reviewed. The onset of action for cetirizine ranged from 59 minutes to 2 hours and 6 minutes and for loratadine onset of action ranged from 1 hour and 42 minutes to none identified during the duration of the study. Cetirizine had a shorter onset of action than loratadine for all comparisons. Fexofenadine had an onset of action within 60 minutes. The literature search did not reveal any published onset of action studies for desloratadine. The onset of action for a given second-generation antihistamine depends on how it is defined and subsequently measured.

Determination of loratadine in human plasma by HPLC with fluorescence detector and study on its bioavailability

AIM

To establish an HPLC-fluorescence method for determination of loratadine in human plasma and evaluate its relative bioavailability.

METHODS

An Alltech-C18 column and a mobile phase of acetonitrile-water-glacial acetic acid-triethylamine (90:100:6:0.15) were used. The fluorescence detector was set at Ex 274 nm, Em 450 nm. The flow rate was 1 mL.min-1.

RESULTS

The calibration curve was linear over a concentration range of 0.2-30 micrograms.L-1. The limit of quantification was 0.2 microgram.L-1. The average method recoveries varied from 96% to 98%. The results showed AUC, Tmax, Cmax and T1/2 beta between the testing tablets, testing capsules and reference tablets had no significant difference (P > 0.05). Relative bioavailabilities were 107% +/- 17% and 100% +/- 14% respectively.

CONCLUSION

The three formulations were bioequivalent.

Pharmacokinetic properties of single-dose loratadine and ambroxol alone and combined in tablet formulations in healthy men

BACKGROUND

Due to Mexico's complicated socioeconomic environment, causing a high occurrence of >1 person sharing a single room, respiratory conditions are spread easily. Respiratory conditions are the main reason for consultation with a physician. The most frequent symptoms are throat soreness and cough; therefore, a new formulation combining loratadine and ambroxol hydrochloride was designed to treat these 2 major symptoms. The combination is expected to provide relief when coprescribed with more specific therapies, such as antibiotics.

OBJECTIVE

This study determined the pharmacokinetic profile of single-dose loratadine-ambroxol hydrochloride combination therapy versus each component given separately. The analyses included descarboethoxyloratadine (DCL), the primary active metabolite of loratadine.

METHODS

This was a 4-week, single-center, randomized, open-label, 3-period crossover study in adult male volunteers aged 18 to 50 years and in good general health. Subjects were randomized to receive single doses of treatment A (2 loratadine 5-mg tablets + ambroxol 30-mg tablets), B (2 ambroxol 30-mg tablets), or C (1 loratadine 10-mg tablet) in 1 of 3 sequences (ABC, BCA, or CAB) per period. A 14-day washout period separated each treatment period. Plasma concentration-time data curves for each subject and treatment were analyzed by noncompart-mental methods to obtain values for area under the curve (AUC), maximum plasma concentration (C(max)), and time to reach C(max) (T(max)).

RESULTS

Thirty subjects (mean [SD] age, 22.5 [2.6] years) were enrolled. All treatments were well tolerated. Formulations A and C produced similar loratadine and DCL AUC from time 0 to 24 hours (AUC(0-24)) values, but showed slightly high C(max). values for loratadine and slightly low C(max) values for DCL, indicating failure to demonstrate bioinequivalence. Formulations A and B produced similar ambroxol C(max), T(max), and AUC(0-24) values.

CONCLUSIONS

In this population of healthy mate volunteers, results showed the bioavailability of loratadine and ambroxol from the new formulation and did not show impairment of absorption when the drugs were formulated in a combination tablet.

Pharmacokinetics of loratadine and its active metabolite descarboethoxyloratadine in healthy Chinese subjects

AIM

To investigate the pharmacokinetics of loratadine (LOR) and its active metabolite descarboethoxyloratadine (DCL) in healthy Chinese subjects.

METHODS

Twenty healthy Chinese male subjects received a single oral dose of LOR 20 mg. A sensitive liquid chromatography-tandem mass spectrometry method (LC/MS/MS) was used for the determination of LOR and DCL in plasma.

RESULTS

Mean maximum concentration (C(max)) was found (17+/-14) microg/L for LOR at 1.2 h and (16+/-9) microg/L for DCL at 1.5 h. Mean area under the plasma concentration-time curve from zero to infinity (AUC(0-infinity)) was (47+/-49) microg x h x L(-1) for LOR and (181+/-122) microg x h x L(-1) for DCL, respectively. The apparent elimination half-life (T1/2) of LOR was (6+/-4) h, and that of DCL was (13.4+/-2.6) h. The ratios of AUC(DCL)/AUCLOR ranged from 0.36 to 54.5.

CONCLUSION

LOR was rapidly absorbed and transformed to DCL. AUC of the parent drug was extremely variable, while AUC of the active metabolite DCL was moderately variable after an oral dose of LOR to Chinese subjects.

Desloratadine: a nonsedating antihistamine

OBJECTIVE

To review information on desloratadine, a nonsedating antihistamine.

DATA SOURCES

An English-language MEDLINE search was conducted (1966-July 2002). References of identified articles were subsequently reviewed for additional data. Schering Corporation provided unpublished information.

STUDY SELECTION/DATA EXTRACTION

Articles and abstracts pertaining to desloratadine were considered for inclusion, with emphasis on randomized, placebo-controlled, double-blind trials.

DATA SYNTHESIS

Desloratadine is approved for the treatment of symptoms associated with seasonal allergic rhinitis (SAR), perennial allergic rhinitis (PAR), and chronic idiopathic urticaria (CIU) in patients aged > or =12 years. In placebo-controlled trials, desloratadine demonstrated superior efficacy as a once-daily treatment of SAR, PAR, and CIU. Data suggest that desloratadine has antiinflammatory and decongestant activity.

CONCLUSIONS

Desloratadine appears to be a "me-too" agent, with no major differences compared with other second-generation antihistamines.

Clinical pharmacology of H1-antihistamines in the skin

BACKGROUND

The extent of the distribution of H(1)- antihistamines into the skin and H(1)-antihistamine activity in the skin are clinically relevant in the treatment of allergic skin disorders.

METHODS

In a prospective, randomized, double-blind, parallel-group, multiple-dose study, we gave fexofenadine 180 mg, loratadine 10 mg, or chlorpheniramine 8 mg to 21 men (7 in each group). Before dosing and at 1, 3, 6, 9, and 24 hours after the first antihistamine dose as well as at 168, 192, and 216 hours after the first dose (ie, 12, 36, and 60 hours after the seventh and last consecutive daily H(1)-antihistamine dose), we measured fexofenadine, loratadine, or chlorpheniramine concentrations in plasma and in skin tissue samples obtained through use of punch biopsies, along with suppression of histamine-induced skin wheals and flares. Loratadine metabolites, including desloratadine and its metabolites, were not measured, and chlorpheniramine metabolites were not measured.

RESULTS

All 21 participants completed the study. Skin/plasma fexofenadine ratios ranged from 1.2 +/- 0.5 at 1 hour to 110 +/- 74 at 24 hours, and skin fexofenadine concentrations exceeded loratadine and chlorpheniramine skin concentrations at each test time. This was reflected in significant wheal and flare suppression by fexofenadine in comparison with loratadine at 3 hours and in comparison with chlorpheniramine at 6 and 9 hours (wheal) and from 3 to 24 hours and at 192 hours (flare). Compared with fexofenadine, loratadine significantly suppressed the wheal at 192 hours, and compared with chlorpheniramine, it significantly suppressed the wheal at 9 hours and the flare at 24 and 192 hours. At no time did chlorpheniramine suppress the wheal or flare significantly more than fexofenadine or loratadine.

CONCLUSIONS

In skin disorders for which H(1)-antihistamines are recommended, these results support the use of fexofenadine or loratadine, and they indicate the need for reexamination of the use of chlorpheniramine.

Lack of clinically relevant interaction between desloratadine and erythromycin

OBJECTIVE

To evaluate the bioavailability, cardiac safety and tolerability of desloratadine when given in combination with the CYP3A4 inhibitor erythromycin.

DESIGN

A randomised, 2-way crossover, placebo-controlled, third party-blind, multiple dose study.

PARTICIPANTS

24 healthy volunteers (12 men, 12 women) aged 19 to 46 years.

INTERVENTIONS

Oral desloratadine 7.5mg daily in combination with either placebo (n = 24) or erythromycin 500mg every 8 hours (n = 24) for 10 days. After a minimum 7-day washout period, participants crossed over to the alternative regimen.

MAIN OUTCOME MEASURES

ECG parameters.

RESULTS

Desloratadine/erythromycin did not induce clinically or statistically significant changes in any ECG parameter. The maximum corrected QT (QT(c)) interval was 445 msec for both treatments. The peak plasma concentration and area under the plasma concentration-time curve from 0 to 24 hours of desloratadine were slightly increased by 1.2- and 1.1-fold by concomitant administration of erythromycin compared with desloratadine/placebo. Gastrointestinal adverse events were more frequent after desloratadine/erythromycin than desloratadine/placebo (46 vs 4%), reflecting the poor gastrointestinal tolerability of erythromycin. There were no reports of syncope.

CONCLUSION

Combined desloratadine/erythromycin therapy was well tolerated and had no clinically relevant electrocardiographic effects at a dose that was 50% higher than the recommended dose of 5mg. Although coadministration of erythromycin slightly increased plasma concentrations of desloratadine, this change did not correlate with any prolongation of the QT(c) interval, and no toxicity was observed clinically.

Desloratadine has no clinically relevant electrocardiographic or pharmacodynamic interactions with ketoconazole

OBJECTIVE

This study was performed to assess the electrocardiographic safety and pharmacokinetics of desloratadine in combination with the CYP3A4 inhibitor ketoconazole.

DESIGN

A randomised, placebo-controlled, third-party-blind, 2-way crossover study.

PARTICIPANTS

24 healthy volunteers (12 men, 12 women; age 19 to 50 years).

INTERVENTIONS

7.5mg of desloratadine orally per day in combination with placebo or with 200mg of ketoconazole every 12 hours for 10 days. After a minimum 7-day washout period, participants received the alternative treatment.

MAIN OUTCOME MEASURES

ECG parameters.

RESULTS

Comparable maximum corrected QT (QT(c)) intervals were observed after coadministration of desloratadine and placebo or ketoconazole (431 and 435 msec, respectively). The desloratadine/ketoconazole combination did not induce any statistically significant or clinically relevant changes in QT(c), QT, PR or QRS intervals compared with desloratadine alone; ventricular rate was slightly slower when desloratadine was given with ketoconazole. At steady state, coadministration of ketoconazole resulted in no significant change in area under the desloratadine concentration-time curve (AUC) from 0 to 24 hours compared with desloratadine/placebo. Coadministration of desloratadine and ketoconazole resulted in a 1.3-fold increase in desloratadine maximum concentration (C(max)) that was not clinically relevant. The most common adverse event was headache, reported in 42 and 38% of individuals, respectively, after coadministration of desloratadine/placebo and desloratadine/ketoconazole. There were no reports of dizziness or syncope.

CONCLUSION

Coadministration of desloratadine and ketoconazole was well tolerated and was associated with minimal increase in AUC and C(max). The combination did not induce any clinically relevant electrocardiographic changes.

Desloratadine demonstrates dose proportionality in healthy adults after single doses

OBJECTIVE

To evaluate the dose proportionality and linearity and pharmacokinetic profile of desloratadine after single oral doses over the range of 5 to 20mg.

DESIGN

Single centre, randomised, open-label, 4-way crossover study in which healthy adults received single doses of desloratadine (5, 7.5, 10 and 20mg) in 4 different treatment periods. Desloratadine was administered each morning after a 10-hour fast. A washout period of at least 14 days separated each dose. Plasma concentrations were measured prior to each treatment and over the 168 hours after drug administration to determine the area under the plasma concentration-time curve (AUC) and maximum observed plasma concentration (C(max)).

PARTICIPANTS

20 healthy male volunteers (3 White, 17 Black) ranging in age from 19 to 45 (mean 37) years and weighing 54 to 91 (mean 75) kg were enrolled and completed this study.

MAIN OUTCOME MEASURES

The primary parameter to assess dose proportionality and linearity was AUC from time zero to final concentration time point (AUC(S)).

RESULTS

The C(max) for all doses was observed approximately 4 hours after administration, revealing no dose-related differences in absorption rate. The half-life (t((1/2))) ranged from 21.2 to 24.1 hours. C(max) and AUC(S) increased in a dose-proportional manner over a dose range of 5 to 20mg. Although the recommended clinical dose is 5mg, doses up to 20mg were well tolerated.

CONCLUSION

In this study, single doses of desloratadine as high as 4 times the recommended clinical dose of 5mg were well tolerated. The C(max) and AUC(S) for doses of 5 to 20mg increased in a dose-proportional manner.

Effect of race and sex on single and multiple dose pharmacokinetics of desloratadine

OBJECTIVE

This study was designed to characterise the single and multiple dose pharmacokinetic profile of desloratadine, a new antihistamine, and its main metabolite, 3-hydroxy (3-OH) desloratadine, in healthy volunteers differing in sex and race.

DESIGN

An open-label, parallel-group, single- and multiple-dose pharmacokinetic trial.

INTERVENTION

A single 7.5mg oral tablet of desloratadine on day 1, followed by 7.5mg daily doses on days 4 to 17.

PARTICIPANTS

48 healthy, nonsmoking volunteers (12 White men, 12 Black men, 12 White women, 12 Black women).

MAIN OUTCOME MEASURES

AUC(24h) and C(max) determined from serial blood samples of desloratadine and 3-OH desloratadine.

RESULTS

There were no clinically relevant differences between men and women or Black participants and White participants for desloratadine and 3-OH desloratadine maximum plasma concentrations (C(max)) and area under the plasma concentration-time curve (AUC). Following multiple doses, the geometric mean C(max) was 5.17 microg/L in men, 5.68 microg/L in women, 5.87 microg/L in Black participants and 5.00 microg/L in White participants; the corresponding AUC from 0 to 24 hours (AUC(24h)) values were 77.9, 80.0, 90.6 and 68.8 micro g/L x h. Corresponding 3-OH desloratadine geometric mean C(max) values were 1.93, 2.79, 2.20 and 2.45 microg/L, and the AUC(24h) values were 32.1, 47.5, 37.1 and 41.1 microg/L. h.

CONCLUSIONS

Oral administration of multiple doses of desloratadine 7.5mg, a dose 50% higher than the recommended 5mg clinical dose, was well tolerated by healthy adults differing in sex and race. Comparison of the C(max) and AUC values following 14 days of treatment with desloratadine indicates that no dosage adjustment is needed on the basis of sex or race.

Oral bioavailability of desloratadine is unaffected by food

OBJECTIVE

To determine the effect of coadministration of food on the bioavailability of oral desloratadine.

DESIGN

A randomised, open-label, single dose crossover study in which healthy adults received a single, oral dose of desloratadine 7.5mg, 50% greater than the recommended dose of 5mg, under fed or fasted conditions and were then crossed over to receive the other treatment regimen.

PARTICIPANTS

18 healthy volunteers (11 men, 7 women) aged from 18 to 43 (mean 29) years and weighing 54 to 104 (mean 76.4) kg were enrolled and completed this study.

MAIN OUTCOME MEASURES

C(max), AUC(S) and AUC(infinity ).

RESULTS

Maximum mean plasma concentration (C(max)) was 3.53 microg/L in fed compared with 3.30 microg/L in fasted participants. Area under the plasma concentration-time curve from time 0 to time of final quantifiable sample (AUC(S)) mean values were 61.0 microg/L x h in fed and 61.9 microg/L x h in fasted participants. Fed individuals had mean AUC extrapolated to infinity (AUC(infinity )) of 62.5 microg/L x h compared with 63.5 microg/L x h in fasted participants. None of these differences between the fed and fasted state was statistically significant. The most frequently reported adverse event was headache. There were no statistically significant changes in ECG parameters.

CONCLUSION

The results of this study indicate that food has no effect on the oral bioavailability of a single oral dose of desloratadine 7.5mg.

A pharmacokinetic profile of desloratadine in healthy adults, including elderly

OBJECTIVE

To characterise the pharmacokinetic profile of desloratadine and its main metabolite, 3-hydroxy (3-OH) desloratadine, in a patient population representative of the population studied in the desloratadine clinical efficacy and safety studies, including the elderly.

DESIGN

A multicentre, multidose, open-label pharmacokinetic trial.

PARTICIPANTS

113 healthy adult volunteers (57 men, 56 women; 95 White, 18 Black) were enrolled, and 112 completed the study.

INTERVENTIONS

A 5mg oral dose of desloratadine once daily for 10 days.

MAIN OUTCOME MEASURES

C(max), t(max), t((1/2)) and AUC(24h).

RESULTS

Steady-state plasma concentrations were attained by day 7. Peak plasma concentrations (C(max)) of desloratadine (mean 3.98 micro g/L) and 3-OH desloratadine (mean 1.99 micro g/L) were reached at a mean of 3.17 and 4.76 hours (t(max)), respectively, after administration. The area under the plasma concentration-time curve from 0 to 24 hours (AUC(24h)) was 56.9 micro g/L x h for desloratadine and 32.3 micro g/L x h for 3-OH desloratadine. The mean half-lives (t((1/2))) of desloratadine and 3-OH desloratadine were 26.8 and 36 hours, respectively. There were no clinically relevant differences in the calculated pharmacokinetic parameters of desloratadine when participants were stratified into 3 age groups (19 to 45, 46 to 64 and 65 to 70 years). Treatment-emergent adverse events occurred in 31 of the 113 participants (3 of the 17 aged >or=65 years reported adverse events). All adverse events were mild to moderate in severity, and none resulted in discontinuation of treatment. There were no consistent clinically relevant changes in blood pressure, pulse, oral body temperature or electrocardiogram evaluations and no reports of syncope or sedation.

CONCLUSION

Daily administration of desloratadine 5mg is well tolerated. The 27-hour half-life of desloratadine permits once daily administration. No dosage adjustment of desloratadine is required in the elderly.