Clinical Pharmacokinetics and Pharmacodynamics of Desloratadine, Fexofenadine and Levocetirizine

Effects of modified Wendan Decoction combined with acupuncture on inflammatory factors and immune function in urticaria patients

This study aimed to explore the effects of modified Wendan Decoction combined with acupuncture on serum inflammatory markers and immune function in patients suffering from urticaria. A total of 150 urticaria patients admitted to our hospital were randomly assigned to two groups: the observation group (n = 75) and the control group (n = 75). The control group received levocetirizine tablets, while the observation group was treated with modified Wendan Decoction along with acupuncture. Following treatment, the observation group demonstrated a higher clinical efficacy compared to the control group, with a statistically significant difference (P < 0.05). Both groups experienced reductions in symptom scores, including erythema, burning sensation, pruritus, wheals, fever accompanied by epigastric pain, nausea and vomiting, fatigue, and poor appetite. However, the observation group showed significantly lower symptom scores than the control group (P < 0.05). Additionally, levels of IL-4, IL-10, IL-25, IL-33, and IFN-γ decreased in both groups after treatment, but the observation group exhibited lower levels than the control group, again with a statistically significant difference (P < 0.05). The recurrence rate was notably lower in the observation group compared to the control group (P < 0.05). The combination of modified Wendan Decoction and acupuncture effectively reduces serum inflammatory markers and enhances immune function in patients with urticaria. This treatment demonstrates significant clinical effectiveness and holds potential for broader application in clinical settings.

Improving Understanding of Fexofenadine Pharmacokinetics to Assess Pgp Phenotypic Activity in Older Adult Patients Using Population Pharmacokinetic Modeling

BACKGROUND AND OBJECTIVE

Fexofenadine is commonly used as a probe substrate to assess P-glycoprotein (Pgp) activity. While its use in healthy volunteers is well documented, data in older adult and polymorbid patients are lacking. Age- and disease-related physiological changes are expected to affect the pharmacokinetics of fexofenadine. This study aims to investigate the pharmacokinetics of fexofenadine in hospitalized older adult patients as a potential marker of Pgp activity, using data from the OptimAT study (ClinicalTrials.gov identifier: NCT03477331).

METHODS

Population pharmacokinetic (popPK) modeling was conducted using data from 449 hospitalized patients with a median age of 71 years (range: 25-97) and 10 healthy volunteers (median age: 23 years, range: 20-36). Fexofenadine plasma concentrations were analyzed using a refined two-compartment model with sequential zero/first-order absorption, while investigating the impact of covariates such as age, renal function, and Pgp inhibitors on fexofenadine pharmacokinetics.

RESULTS

Age, renal insufficiency, and Pgp inhibitors significantly influenced fexofenadine exposure. Renal function was a key factor, with AUC0-6 increasing by 79% in mild-to-moderate and by 154% in moderate-to-severe renal impairment compared with normal renal function. Co-administration of Pgp inhibitors led to a 35% increase in AUC0-6. Across chronic kidney disease (CKD) stages, age, and Pgp inhibitor status, fexofenadine AUC0-6 ratio ranged from 1.15 (stage 1, 20-30 years) to 4.59 (stage 5, 91-100 years, with Pgp inhibitors), relative to a reference subject of 20 years, normal renal function, and no Pgp inhibitors.

CONCLUSION

Clinicians should consider the risk of Pgp substrate accumulation in older adults, particularly those with advanced renal impairment. We propose typical values stratified by age and renal function to assist in interpreting Pgp phenotyping using fexofenadine exposure, thereby supporting drug optimization in this population. Further studies are needed to explore underlying mechanisms, such as reduced Pgp activity or expression.

Desloratadine mitigates hepatocellular carcinoma in rats: Possible contribution of TLR4/MYD88/NF-κB pathway

Chemotherapeutic medication-induced systemic toxicity makes cancer treatment less effective. Thus, the need for drug repurposing, which aids in the development of safe and efficient cancer therapies, is urgent. The primary goal of this research was to assess desloratadine hepatoprotective abilities and its capacity to attenuate TLR4/MyD88/NF-κB inflammatory pathway in hepatocellular carcinoma (HCC) induced by thioacetamide (TAA). Male Sprague Dawely rats received TAA injections (200 mg/kg, i.p., 2 times/week) for 16 weeks. To confirm the development of HCC, liver function biomarkers and histopathological analysis were evaluated. Desloratadine (5 mg/kg, p.o.) was administered to rats in 2 treatment groups; HCC + DES 1 group received desloratadine with TAA for 1 month from week 13-16, HCC + DES 2 group received desloratadine with TAA for 2 months from week 9-16. Chronic TAA administration resulted in considerable overexpression of the profibrogenic cytokine TGF-β and elevation in protein expression of NF-κB besides levels of TLR4, MyD88, TRAF6, TAK1 and IL-1β. Desloratadine administration showed a significant improvement in liver function tests, as well as an increase in tissue antioxidant enzymes and an improvement in the liver's histopathological features. Collectively, desloratadine through modulating TLR4/MyD88/TRAF6/TAK1/NF-κB and acting as an antioxidant, is a promising treatment for HCC induced by TAA.

Clinical Pharmacokinetics of Fexofenadine: A Systematic Review

Background/Objectives: Fexofenadine hydrochloride is a widely prescribed drug for treating histamine-mediated allergic reactions. This review systematically collates existing research on the clinical pharmacokinetics (PK) of fexofenadine, with a copious emphasis on examining the impact of stereoisomerism, disease states, and drug interactions. Methods: The search engines PubMed, Science Direct, Google Scholar, and Cochrane were scanned systematically for articles concerning the clinical PK of fexofenadine in humans. The extensive literature search yielded 85 articles meeting the inclusion standards. Results: The PK parameters of fexofenadine showed a linear correlation between increasing doses and proportional elevations in PK parameters such as area under the curve from time 0 to infinity (AUC0-∞) and maximum plasma concentration (Cmax). Under fed conditions, its bioavailability was reduced by approximately 50%. Findings from patients with end-stage renal disease (ESRD) displayed a 63% decline in oral clearance (CL/F) of fexofenadine. A drug-food interaction study has displayed that grapefruit juice decreased Cmax (201 ng/mL vs. 128 ng/mL), accompanied by a 30% reduction in the bioavailability of fexofenadine. Furthermore, a drug-herb interaction study with St John's Wort (SJW) has reported a reduction in CL/F by 10% after a single dose, but long-term administration reversed this effect, resulting in elevated CL/F by 17% of fexofenadine. Conclusions: Since no prior systematic review on the PK of this drug exists, this review amalgamates all pertinent PK parameters in humans by pooling up-to-date data from published studies. This detailed literature review can be advantageous for researchers who want to develop and assess PK models.

H1 Antihistamines-Promising Candidates for Repurposing in the Context of the Development of New Therapeutic Approaches to Cancer Treatment

Despite significant progress in the field of clinical oncology in terms of diagnostic and treatment methods, the results of anticancer therapy are still not fully satisfactory, especially due to limited response and high toxicity. This has forced the need for further research to finding alternative ways to improve success rates in oncological treatment. A good solution to this problem in the context of rapidly obtaining an effective drug that works on multiple levels of cancer and is also safe is the global strategy of repurposing an existing drug. Research into other applications of an existing drug enables a precise assessment of its possible mechanisms of action and, consequently, the broadening of therapeutic indications. This strategy is also supported by the fact that most non-oncological drugs have pleiotropic effects, and most of the diseases for which they were originally intended are multifactorial, which in turn is a very desirable phenomenon due to the heterogeneous and multifaceted biology of cancer. In this review, we will mainly focus on the anticancer potential of H1 antihistamines, especially the new generation that were not originally intended for cancer therapy, to highlight the relevant signaling pathways and discuss the properties of these agents for their judicious use based on the characteristic features of cancer.

Data mining in FAERS: association of newer-generation H1-antihistamines with nervous system disorders

BACKGROUND

H1-antihistamines are widely used to treat symptoms depending on histamine release in a variety of conditions. However, neurological adverse events have been reported in post-marketing surveillance studies and there are limited literatures comparing the neurological disorders associated with newer-generation H1-antihistamines from real-world datasets.

AIMS

We performed a comparative analysis of nervous system disorders and several newer-generation H1-antihistamines including: cetirizine, loratadine, levocetirizine, desloratadine and fexofenadine.

METHODS

Disproportionality analysis was used to identify the suspected drug neurological adverse events associated with H1-antihistamines of interest via the Food and Drug Administration Adverse Event Reporting System. The proportional reporting ratio (PRR), χ2 (chi-square) and the reporting odds ratio (ROR) with 95% confidence interval (CI) were used to estimate the association.

RESULTS

AE reports of 43,815 cases from 2017 to 2021 were extracted from FAERS. The H1-antihistamines included in our study were associated with various neurological adverse events that could be classified into 12 aspects, containing 42 preferred terms. The majority of adverse event reports were concentrated at somnolence: cetirizine [N = 1342, ROR (95%CI) = 11.8 (11.2-12.5), PRR = 10.8, χ2 = 11755.4], levocetirizine [N = 1276, ROR(95%CI) = 28.5 (26.7-30.3), PRR = 22.7, χ2 = 26218.4], loratadine[N = 516, ROR(95%CI) = 4.6 (4.2-5.0), PRR = 4.4, χ2 = 1378.1], desloratadine [N = 33, ROR(95%CI) = 6.1 (4.3-8.6), PRR = 5.8, χ2 = 131.9], fexofenadine [N = 498, ROR(95%CI) = 5.0 (4.6-5.5), PRR = 4.8, χ2 = 1519.0].

CONCLUSION

Neurological AEs associated with individual newer generation H1-antihistamines of interest varies a lot, whereas somnolence was the most common AE reports. Fexofenadine was highly associated with headaches. Sedative effects associated with levocetirizine and cetirizine should arouse more concern. Seizures significantly associated with levocetirizine and desloratadine were infrequently reported, further research is needed to avoid possible serious outcomes. Patients taking cetirizine probably have higher risk of dystonia and anticholinergic syndrome.

The novel TFEB agonist desloratadine ameliorates hepatic steatosis by activating the autophagy-lysosome pathway

The autophagy-lysosome pathway plays an essential role in promoting lipid catabolism and preventing hepatic steatosis in non-alcoholic fatty liver disease (NAFLD). Transcription factor EB (TFEB) enhances the autophagy-lysosome pathway by regulating the expression of genes related to autophagy and lysosome biogenesis. Therefore, targeting TFEB provides a novel strategy for the treatment of lipid metabolic diseases. In this study, the antiallergic drug desloratadine was screened and identified as a novel TFEB agonist. Desloratadine effectively induced translocation of TFEB to the nucleus and promoted autophagy and lysosome biogenesis. Desloratadine-induced TFEB activation was dependent on AMPK rather than mTORC1. Moreover, desloratadine treatment enhanced clearance of lipid droplets in cells induced by fatty acids oleate and palmitate. Furthermore, high-fat diet (HFD) induced obesity mouse model experiments indicated treatment with desloratadine markedly reduced the body weight of HFD-fed mice, as well as the levels of hepatic triglycerides and total cholesterol, serum glutamic pyruvic transaminase and glutamic-oxaloacetic transaminase. Oil red O staining showed the liver fat was significantly reduced after desloratadine treatment, and H&E staining analysis demonstrated hepatocellular ballooning was improved. In addition, autophagy and lysosomal biogenesis was stimulated in the liver of desloratadine treated mice. Altogether, these findings demonstrate desloratadine ameliorates hepatic steatosis through activating the TFEB-mediated autophagy-lysosome pathway, thus desloratadine has an exciting potential to be used to treat fatty liver disease.

Computational modeling (in silico) methods combined with ecotoxicological experiments (in vivo) to predict the environmental risks of an antihistamine drug (loratadine)

This study employed computational modeling (in silico) methods, combined with ecotoxicological experiments (in vivo) to predict the persistence/biodegradability, bioaccumulation, mobility, and ecological risks of an antihistamine drug (Loratadine: LOR) in the aquatic compartment. To achieve these goals, four endpoints of the LOR were obtained from different open-source computational tools, namely: (i) "STP total removal"; (ii) Predicted ready biodegradability; (iii) Octanol-water partition coefficient (KOW); and (iv) Soil organic adsorption coefficient (KOC). Moreover, acute and chronic, ecotoxicological assays using non-target freshwater organisms of different trophic levels (namely, algae Pseudokirchneriella subcapitata; microcrustaceans Daphnia similis and Ceriodaphnia dubia; and fish Danio rerio), were used to predict the ecological risks of LOR. The main results showed that LOR: (i) is considered persistent (after a weight-of-evidence assessment) and highly resistant to biodegradation; (ii) is hydrophobic (LOG KOW = 5.20), immobile (LOG KOC = 5.63), and thus, it can potentially bioaccumulate and/or can cause numerous deleterious effects in aquatic species; and (iii) after ecotoxicological evaluation is considered "toxic" and/or "highly toxic" to the three trophic levels tested. Moreover, both the ecotoxicological assays and risk assessment (RQ), showed that LOR is more harmful for the crustaceans (RQcrustaceans = moderate to high risks) than for algae and fish. Ultimately, this study reinforces the ecological concern due to the indiscriminate disposal of this antihistamine drug in worldwide aquatic ecosystems.

In Vivo Activity of Intestinal P-Glycoprotein and Hepatic Organic Anion Transporters Polypeptide in Pregnancy and Postpartum

This study investigates the influence of pregnancy on the in vivo activity of the intestinal P-glycoprotein (P-gp) and hepatic organic anion transporters polypeptide (OATP/BCRP) using, respectively, fexofenadine and rosuvastatin as probe drugs. Eleven healthy participants were investigated during the third trimester of pregnancy (Phase 1, 28 to 38 weeks of gestation) and in the postpartum period (Phase 2, 8 to 12 weeks postpartum). In both phases, after administration of a single oral dose of fexofenadine (60 mg) and rosuvastatin (5 mg), serial blood samples were collected for up to 24 h. Rosuvastatin and fexofenadine in plasma were analyzed by LC-MS/MS using previously validated methods. The pharmacokinetic parameters of fexofenadine and rosuvastatin (Phoenix WinNonLin software) with normal distribution (Shapiro-Wilk test) are presented as geometric mean and 90% confidence interval. Phases 1 and 2 were compared using the t test (P < .05). Fexofexadine AUC0-24 values do not differ (P-value: .0715) between Phase 1 (641.9 ng h/mL [500.6-823.1]) and Phase 2 (823.8 ng h/mL [641.5-1057.6]) showing that pregnancy (third trimester) does not alter intestinal P-gp activity. However, rosuvastatin AUC0-24 values are higher (P-value: .00005) in Phase 1 (18.7 ng h/mL [13.3-26.4]) when compared to Phase 2 (9.5 ng h/mL [6.7-13.4]), suggesting inhibition of OATP1B1/OATP1B3 transporters. In conclusion, pregnancy assessed during the third trimester does not alter the intestinal P-gp activity but reduces the activity of hepatic OATP1B1/OATP1B3 transporters. Therefore, adjustments in dosage regimens may be necessary for drugs with low therapeutic index, substrates of the OATP1B1/OATP1B3 transporters, administered during the third trimester of pregnancy.

Tuning fluorescence of fexofenadine by switching OFF intramolecular photoinduced electron transfer: Application to development of one-step green and high throughput microwell spectrofluorimetric assay for analysis of tablets and plasma

Fexofenadine (FEX) is a non-sedating antihistamine commonly used for the treatment of allergic conditions such as seasonal rhinitis and chronic idiopathic urticaria. This study describes the tuning "ON" the intrinsic fluorescence of FEX by switching "OFF" its intramolecular photoinduced electron transfer (PET) through the protonation of the piperidinyl nitrogen atom using sulfuric acid. The resulting fluorescence was utilized as a basis for the development of a highly sensitive microwell spectrofluorimetric assay (MW-SFA) for the one-step determination of FEX in pharmaceutical tablets and plasma. The linear range of the assay was 10-500 ng ml-1, and its limit of quantitation was 25.9 ng ml-1. The proposed MW-SFA was successfully applied to analyze FEX in pharmaceutical tablets and plasma samples, demonstrating good accuracy and precision. The greenness of the assay was confirmed using three metric assessment tools. In conclusion, the MW-SFA is a straightforward, single-step analysis that requires no experimental adjustments. It offers high sensitivity, efficient sample processing, and environmental sustainability. This assay is highly recommended for pharmaceutical quality control and clinical lab use, particularly for measuring FEX levels.

Poor Rhinitis and Asthma Control Is Associated With Decreased Health-Related Quality of Life and Utilities: A MASK-air Study

BACKGROUND

Allergic rhinitis (AR) and asthma may affect health-related quality of life. However, national estimates on the quality of life of patients with AR or asthma are lacking.

OBJECTIVE

To provide estimates for utility scores and EuroQoL five-dimension (EQ-5D) visual analog scale (VAS) for patients with AR or asthma.

METHODS

We conducted a cross-sectional study using direct patient data from the MASK-air app on European MASK-air users with self-reported AR or asthma. We used a multi-attribute instrument (EQ-5D) to measure quality of life (as utility scores and EQ-5D VAS values). Mean scores were calculated per country and disease control level using multilevel regression models with poststratification, accounting for age and sex biases.

RESULTS

We assessed data from 7905 MASK-air users reporting a total of up to 82,737 days. For AR, utilities ranged from 0.86 to 0.99 for good control versus 0.72 to 0.85 for poor control; EQ-5D VAS levels ranged from 78.9 to 87.9 for good control versus 55.3 to 64.2 for poor control. For asthma, utilities ranged from 0.84 to 0.97 for good control versus 0.73 to 0.87 for poor control; EQ-5D VAS levels ranged from 68.4 to 81.5 for good control versus 51.4 to 64.2 for poor control. Poor disease control was associated with a mean loss of 0.14 utilities for both AR and asthma. For the same control levels, AR and asthma were associated with similar utilities and EQ-5D VAS levels. However, lower values were observed for asthma plus AR compared with AR alone.

CONCLUSIONS

Poor AR or asthma control are associated with reduced quality of life. The estimates obtained from mobile health data may provide valuable insights for health technology assessment studies.

Calcium and Neural Stem Cell Proliferation

Intracellular calcium plays a pivotal role in central nervous system (CNS) development by regulating various processes such as cell proliferation, migration, differentiation, and maturation. However, understanding the involvement of calcium (Ca2+) in these processes during CNS development is challenging due to the dynamic nature of this cation and the evolving cell populations during development. While Ca2+ transient patterns have been observed in specific cell processes and molecules responsible for Ca2+ homeostasis have been identified in excitable and non-excitable cells, further research into Ca2+ dynamics and the underlying mechanisms in neural stem cells (NSCs) is required. This review focuses on molecules involved in Ca2+ entrance expressed in NSCs in vivo and in vitro, which are crucial for Ca2+ dynamics and signaling. It also discusses how these molecules might play a key role in balancing cell proliferation for self-renewal or promoting differentiation. These processes are finely regulated in a time-dependent manner throughout brain development, influenced by extrinsic and intrinsic factors that directly or indirectly modulate Ca2+ dynamics. Furthermore, this review addresses the potential implications of understanding Ca2+ dynamics in NSCs for treating neurological disorders. Despite significant progress in this field, unraveling the elements contributing to Ca2+ intracellular dynamics in cell proliferation remains a challenging puzzle that requires further investigation.

Molecular mechanism of antihistamines recognition and regulation of the histamine H1 receptor

Histamine receptors are a group of G protein-coupled receptors (GPCRs) that play important roles in various physiological and pathophysiological conditions. Antihistamines that target the histamine H1 receptor (H1R) have been widely used to relieve the symptoms of allergy and inflammation. Here, to uncover the details of the regulation of H1R by the known second-generation antihistamines, thereby providing clues for the rational design of newer antihistamines, we determine the cryo-EM structure of H1R in the apo form and bound to different antihistamines. In addition to the deep hydrophobic cavity, we identify a secondary ligand-binding site in H1R, which potentially may support the introduction of new derivative groups to generate newer antihistamines. Furthermore, these structures show that antihistamines exert inverse regulation by utilizing a shared phenyl group that inserts into the deep cavity and block the movement of the toggle switch residue W4286.48. Together, these results enrich our understanding of GPCR modulation and facilitate the structure-based design of novel antihistamines.

P-glycoprotein mechanical functional analysis using in silico molecular modeling: Pharmacokinetic variability according to ABCB1 c.2677G > T/A genetic polymorphisms

P-glycoprotein (P-gp) is a widely membrane-expressed multi-drug transporter. It is unclear whether the pharmacokinetic diversity of P-gp substrates is highly dependent on ABCB1 polymorphisms encoding P-gp. The purpose of this study is to analyze the mechanistic function of P-gp through in silico molecular modeling and to approach the resolution of controversy over pharmacokinetic differences according to ABCB1 polymorphisms. P-gp conformations of apo, ligand-docked, and outward-facing states can be modeled based on structural information of human P-gp. And polymorphic P-gp structures were constructed through homology modeling. ABCB1 c.2677G > T/A (Ala893Ser/Thr), did not correspond to P-gp's nucleotide-binding-domain (NBD) or drug-binding-pocket (DBP) or involve mechanical conformational changes. Although amino acid substitution by ABCB1 c.2677G > T/A caused a 30 % increased strain in an α-helix hinge between the NBD and DBP in P-gp's internal tunnel, there were no overall structural changes compared to wild-type. ABCB1 c.2677G > T/A may increase torsional energy, impacting conformational change rate, but this does not significantly affect P-gp's general functioning. Fexofenadine docking into P-gp's DBP explained the substrate interaction, but no effect by ABCB1 c.2677G > T/A was confirmed. Our findings provide additional insights useful in resolving the debate about the influence of ABCB1 polymorphisms on the interindividual pharmacokinetic variability of P-gp substrates.

Targeting spinal microglia with fexofenadine-loaded nanoparticles prolongs pain relief in a rat model of neuropathic pain

Targeting microglial activation is emerging as a clinically promising drug target for neuropathic pain treatment. Fexofenadine, a histamine receptor 1 antagonist, is a clinical drug for the management of allergic reactions as well as pain and inflammation. However, the effect of fexofenadine on microglial activation and pain behaviors remains elucidated. Here, we investigated nanomedicinal approach that targets more preferentially microglia and long-term analgesics. Fexofenadine significantly abolished histamine-induced microglial activation. The fexofenadine-encapsulated poly(lactic-co-glycolic acid) nanoparticles (Fexo NPs) injection reduced the pain sensitivity of spinal nerve ligation rats in a dose-dependent manner. This alleviation was sustained for 4 days, whereas the effective period by direct fexofenadine injection was 3 h. Moreover, Fexo NPs inhibited microglial activation, inflammatory signaling, cytokine release, and a macrophage phenotype shift towards the alternative activated state in the spinal cord. These results show that Fexo NPs exhibit drug repositioning promise as a long-term treatment modality for neuropathic pain.

Improved survival in several cancers with use of H1-antihistamines desloratadine and loratadine

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Improved cancer survival with use of antihistamines desloratadine and loratadine.

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Improved survival seen in tumors that respond to immune checkpoint therapy.

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A – potentially immunological – anti-tumor effect of desloratadine and loratadine.

Background

We have previously shown an association with substantially improved survival in breast cancer and melanoma for desloratadine and loratadine users, and set out to find whether an improved survival can be seen in tumors with and without a known response to immune checkpoint therapy, such as anti-CTLA-4 or anti-PD-1.

Methods

We investigated survival and use of six common H₁-antihistamines (cetirizine, clemastine, desloratadine, ebastine, fexofenadine and loratadine) in a nation-wide cohort of all 429,198 Swedish patients with ten types of immunogenic (gastric, colorectal/anal, pancreatic, lung, breast, prostate, kidney, and bladder cancer, melanoma and Hodgkin lymphoma) and six non-immunogenic (liver, uterine, ovarian, brain/CNS, and thyroid cancer and non-Hodgkin lymphoma) tumors diagnosed 2006–2017. Follow-up was until 2019–02–24.

Findings

Desloratadine use was associated with an improved survival for all immunogenic tumors, but not for the non-immunogenic ones. Loratadine use was associated with improved survival for some tumors. Use of the other antihistamines could not be shown to be consistently associated with improved survival to a statistically significant degree.

Interpretation

Our hypothesis is that our findings result from immune checkpoint inhibition, and we believe both desloratadine and loratadine should be tested in randomized clinical trials as treatment of immunogenic tumors, with priority given to trials of desloratadine as treatment of tumors with few therapy options and dismal prognoses, such as pancreatic cancer. If our results can be confirmed in a clinical setting, new, potentially curative, therapies could result for several tumors, including ones with dire prognoses and limited treatment options.

Contemporary Role and Regulation of Over-the-Counter Sinonasal Medications

OBJECTIVE

Numerous pharmaceutical options are available over-the-counter (OTC) for the relief of sinonasal symptoms. Patients typically utilize these drugs in an unsupervised manner, without appreciation of their relative efficacy or potential for adverse effects. This review covers the scope and regulation of the OTC drug market, the pros and cons of OTC availability, and specific concerns that surround the most common classes of OTC sinonasal drugs. Suggestions are provided for the improvement of patient care and public health.

DATA SOURCES

MEDLINE publications and market reports.

REVIEW METHODS

Literature review.

CONCLUSIONS

Some of the most commonly used OTC sinonasal remedies, including decongestants and first-generation antihistamines, are less effective than alternative drugs and pose potential safety concerns.

IMPLICATIONS FOR PRACTICE

Clinicians should advocate to their patients for the appropriate use of alternative agents, such as intranasal corticosteroids and newer-generation antihistamines, and discourage the unsupervised use of oral and topical decongestants. Furthermore, health care practitioners should encourage dialogue with their patients about the use of OTC sinonasal remedies, with the goals of optimizing individual health and health care delivery.

Levocetirizine Oral Disintegrating Tablet: A Randomized Open-Label Crossover Bioequivalence Study in Healthy Japanese Volunteers

Levocetirizine is classified as a second-generation antihistamine. Levocetirizine is available for the treatment of allergic disorders such as allergic rhinitis and chronic idiopathic urticaria. This was a single-center, single-dose, open-label, randomized, 2-way crossover study in healthy Japanese male subjects consisting of 2 parts. Part 1 compared the bioavailability of levocetirizine oral disintegrating tablet (ODT) and levocetirizine immediate-release tablet (IRT) taken with water in the fasted state in 24 subjects; all subjects completed this part of the trial. In part 2, the bioavailability of levocetirizine ODT without water was compared with that of levocetirizine IRT with water in the fasted state in 48 subjects; 47 subjects completed this part of the trial. Bioequivalence was demonstrated between levocetirizine IRT 5 mg and ODT 5 mg. The safety profiles were generally similar between levocetirizine ODT and levocetirizine IRT, with no serious adverse events, deaths, or adverse events leading to withdrawal reported during the study.

Desloratadine and loratadine stand out among common H1-antihistamines for association with improved breast cancer survival

BACKGROUND

As tumors maintain an inflammatory microenvironment, anti-inflammatory medication can be useful in cancer therapy. We have previously shown an association with improved survival in melanoma for use of the H₁-antihistamines desloratadine and loratadine, and here we examine use of H₁-antihistamines and breast cancer mortality.

MATERIAL AND METHODS

We investigated use of the six major H₁-antihistamines (cetirizine, clemastine, desloratadine, ebastine, fexofenadine and loratadine) and breast cancer-specific and overall mortality in a nation-wide register-based study of all 61,627 Swedish women diagnosed with breast cancer 2006-2013. Both peri- and post-diagnostic antihistamine use was analyzed using Cox regression models. Analyses were stratified for age and subgroup analyses based on estrogen receptor status and menopausal status were performed.

RESULTS

We found a consistently improved survival of desloratadine users (HR = 0.67; 95% CI 0.55-0.81, p < .001), as well as of loratadine users (HR = 0.80; 95% CI 0.67-0.95, p = .012), relative to nonusers, regardless of patient age, menopause, estrogen receptor status or stage of the tumor, or whether breast cancer-specific or overall survival was analyzed. The survival of users of other antihistamines varied relative to non-users.

CONCLUSION

Based on their safety and current use within the patient population, together with our observations, we suggest the initiation of trials of desloratadine and loratadine as treatment of breast cancer as well as studies of the mechanism behind their possible effect. Further studies on any effects of other H₁-antihistamines may also be merited, as well as of H₁-antihistamine use and survival in other malignancies.

Sex differences in the pharmacology of itch therapies-a narrative review

BACKGROUND

Chronic itch is the most common skin-related condition, associated with a high psychosocial and economic burden. In recent years, increasing evidence of sex differences in the perception, clinical presentation and treatment requirements of itch points towards potential benefits when using sex-adapted therapies. It is well-known that body composition, absorption, metabolism, elimination and adverse drug reactions (ADRs) differ between sexes, but only little is known about the impact of sex in the pharmacology of itch treatments, which could help to rationalise sex-adapted treatment strategies.

AIM

To evaluate and review sex effects in the pharmacokinetics and /-dynamics of drugs used to treat itch.

METHODS

In this narrative review we performed a PubMed and MEDLINE (Ovid) search using the terms (itch OR pruritus) AND (gender OR sex) AND (drug OR medication OR pharmacokinetics OR pharmacodynamics). Additional searches were performed for the topical and systemic drugs recommended by the European Guideline on Chronic Pruritus.

RESULTS

We found numerous reports with variable levels of evidence of sex effects with respect to the pharmacokinetics and/or pharmacodynamics of 14 drug classes used for the treatment of itch, including a total of 19 systemic and 3 topical drugs. Women seem to present higher plasma levels of several drugs used in itch treatment, including tri- and tetracyclic antidepressants (e.g. doxepin, amitriptyline, mirtazapine), serotonin reuptake inhibitors (e.g. paroxetine, sertraline, fluoxetine), immunosuppressive drugs (e.g. cyclosporine, mycophenolate mofetil), serotonin receptor antagonists (e.g. ondansetron) and betablockers (e.g. propranolol). Adverse drug reactions (ADRs) were generally more common in women. Being female was reported to be an independent risk factor for QTc-prolongation associated with antihistamines and tetracyclic antidepressants. Additionally, women seem to be more prone to sedative effects of antihistamines, and to suffer from a higher frequency as well as severity of side effects with systemic calcineurin inhibitors, opioid agonists, and opioid antagonists. Women were also sensitised more often to topically applied drugs. Of note, apart from only one experimental study with capsaicin, none of these reports were designed specifically to assess the effect of sex (and gender) in the treatment of itch.

DISCUSSION/CONCLUSION

Our review supports previous reports that sex is of importance in the pharmacokinetics and /-dynamics of several drugs used to treat itch although those drugs were mostly evaluated for non-itch indications. However, the results are limited by methodological limitations evident in most studies such as underrepresentation of women in clinical trials. This emphasises the need to study the impact of sex (and gender) in future itch trials to yield better outcomes and prevent ADRs in both sexes.

Pharmacological Management of Allergic Rhinitis in the Elderly

Recent studies suggest that allergic rhinitis is highly prevalent in the elderly population, but is underdiagnosed and undertreated. This review article briefly introduces allergic rhinitis in the elderly (epidemiology and pathophysiology) and identifies the main goals of treatment in these patients with respect to age-related physiological factors, comorbid conditions and polypharmacy. The primary focus of the article is a narrative review of the literature concerning the different types of treatment options in elderly patients aged 60+ years (pharmacological therapy and allergen-specific immunotherapy). The main management trend for allergic rhinitis in elderly patients is the same as the trend in young patients. Second-generation antihistamines and nasal glucocorticosteroids are also the first-line therapies in seniors. In a few trials, allergen-specific immunotherapy for grass pollen or house dust mites has been shown to be effective and safe in patients aged 60 years or older with allergic rhinitis. In conclusion, undertreatment of allergic rhinitis in the elderly is a reality. Pharmacological treatment is quite similar in both older and younger patients with allergic rhinitis.

Second generation H1 - antihistamines interaction with food and alcohol-A systematic review

Histamine is a mediator of many physiological processes. It plays an important role in modulating allergy reactions and immune system responses. H1 receptor is a therapeutic target for drugs applied in allergic diseases such as allergic rhinoconjunctivitis, urticarial, or atopic dermatitis. H1-antihistamines display different chemical structures, pharmacokinetics and a potential for drug-drug and drug-food interactions. Drug-food interactions are known to reduce therapeutic effects of the medicine, as well as to induce a potent adverse drug reactions. Considering it all, a systematic review was conducted to investigate the importance of drug-food interaction for H1-antihistamine drugs. As non-sedating second generation H1-antihistamines remain to be drugs of choice in treating allergic conditions, the review has been focused on this particular class of medicines. The aim of this paper is to examine the evidence of food-drug and food-alcohol interactions for second generation H1-antihistamine drugs. A systematic literature queries were performed in the following databases: Medline (via PubMed), Cochrane Library, Embase and Web of Science (all from their inception date till October 2016). The queries covered nine specific names of second generation anthistamine drugs, namely bilastine, cetirizine, desloratadine, ebastine, fexofenadine, levocetirizine, loratadine, mizolastine, and rupatadine, in combinations with such terms as "food", "juice", "grapefruit", "fruits", "alcohol", "pharmacokinetics", and "meal". Additional publications were found by checking all the reference lists. Where none data on drug-food interaction could be found within the investigated databases, a specific drug prescribing information was used. 2326 publications were identified with the database queries. Articles were subjected to analysis by reviewing their title, abstract and full text; duplicated papers were removed. Having collected a complete set of data, a critical review was undertaken. For selected H1-antihistamines food, fruit juices or alcohol consumption may significantly impact the efficacy and safety of the therapy. This issue shall be well understood to educate patients properly, as it provides the major therapeutic element in allergic diseases.

Updosing of Nonsedating Anti-histamines in Recalcitrant Chronic Urticaria

Chronic urticaria (CU) is a persistent, debiliating condition that causes severe impairment on the quality of life (QoL) of patient by interrupting work productivity. Current guidelines recommend second-generation (nonsedating) anti-histamines for the treatment for all forms of urticaria. In patients who do not respond adequately to conventional doses of anti-histamines, it is recommended to increase the dose to up to four times to obtain control. But there are only few controlled studies that have assessed the efficacy and safety of nonsedating anti-histamines. Though sedating histamines are frequently used as an add-on therapy in severe cases, they have a negative impact on QoL by compromising sleep and performance. The use of other suggested therapeutic options (omalizumab, cyclosporine A, montelukast and dapsone) is also limited by paucity of data on their efficacy and adverse effect profile. Second-generation anti-histamines which are relatively safer require more proven data to support their judicious use to improve disease in patients with CU.

A convenient route to symmetrically and unsymmetrically substituted 3,5-diaryl-2,4,6-trimethylpyridines via Suzuki-Miyaura cross-coupling reaction

A series of differently substituted 3,5-diaryl-2,4,6-trimethylpyridines were prepared and characterized using the Suzuki-Miyaura coupling reaction with accordingly selected bromo-derivatives and arylboronic acids. The reaction conditions were carefully optimized allowing high yield of isolated products and also the construction of unsymmetrically substituted diarylpyridines, difficult to access by other methods.

Cherry-picked ligands at histamine receptor subtypes

Histamine, a biogenic amine, is considered as a principle mediator of multiple physiological effects through binding to its H1, H2, H3, and H4 receptors (H1-H4Rs). Currently, the HRs have gained attention as important targets for the treatment of several diseases and disorders ranging from allergy to Alzheimer's disease and immune deficiency. Accordingly, medicinal chemistry studies exploring histamine-like molecules and their physicochemical properties by binding and interacting with the four HRs has led to the development of a diversity of agonists and antagonists that display selectivity for each HR subtype. An overview on H1-R4Rs and developed ligands representing some key steps in development is provided here combined with a short description of structure-activity relationships for each class. Main chemical diversities, pharmacophores, and pharmacological profiles of most innovative H1-H4R agonists and antagonists are highlighted. Therefore, this overview should support the rational choice for the optimal ligand selection based on affinity, selectivity and efficacy data in biochemical and pharmacological studies. This article is part of the Special Issue entitled 'Histamine Receptors'.

International Union of Basic and Clinical Pharmacology. XCVIII. Histamine Receptors

Histamine is a developmentally highly conserved autacoid found in most vertebrate tissues. Its physiological functions are mediated by four 7-transmembrane G protein-coupled receptors (H1R, H2R, H3R, H4R) that are all targets of pharmacological intervention. The receptors display molecular heterogeneity and constitutive activity. H1R antagonists are long known antiallergic and sedating drugs, whereas the H2R was identified in the 1970s and led to the development of H2R-antagonists that revolutionized stomach ulcer treatment. The crystal structure of ligand-bound H1R has rendered it possible to design new ligands with novel properties. The H3R is an autoreceptor and heteroreceptor providing negative feedback on histaminergic and inhibition on other neurons. A block of these actions promotes waking. The H4R occurs on immuncompetent cells and the development of anti-inflammatory drugs is anticipated.

A long-standing mystery solved: the formation of 3-hydroxydesloratadine is catalyzed by CYP2C8 but prior glucuronidation of desloratadine by UDP-glucuronosyltransferase 2B10 is an obligatory requirement

Desloratadine (Clarinex), the major active metabolite of loratadine (Claritin), is a nonsedating long-lasting antihistamine that is widely used for the treatment of allergic rhinitis and chronic idiopathic urticaria. For over 20 years, it has remained a mystery as to which enzymes are responsible for the formation of 3-hydroxydesloratadine, the major active human metabolite, largely due to the inability of any in vitro system tested thus far to generate this metabolite. In this study, we demonstrated that cryopreserved human hepatocytes (CHHs) form 3-hydroxydesloratadine and its corresponding O-glucuronide. CHHs catalyzed the formation of 3-hydroxydesloratadine with a Km of 1.6 μM and a Vmax of 1.3 pmol/min per million cells. Chemical inhibition of cytochrome P450 (P450) enzymes in CHHs demonstrated that gemfibrozil glucuronide (CYP2C8 inhibitor) and 1-aminobenzotriazole (general P450 inhibitor) inhibited 3-hydroxydesloratadine formation by 91% and 98%, respectively. Other inhibitors of CYP2C8 (gemfibrozil, montelukast, clopidogrel glucuronide, repaglinide, and cerivastatin) also caused extensive inhibition of 3-hydroxydesloratadine formation (73%-100%). Assessment of desloratadine, amodiaquine, and paclitaxel metabolism by a panel of individual CHHs demonstrated that CYP2C8 marker activity robustly correlated with 3-hydroxydesloratadine formation (r(2) of 0.70-0.90). Detailed mechanistic studies with sonicated or saponin-treated CHHs, human liver microsomes, and S9 fractions showed that both NADPH and UDP-glucuronic acid are required for 3-hydroxydesloratadine formation, and studies with recombinant UDP-glucuronosyltransferase (UGT) and P450 enzymes implicated the specific involvement of UGT2B10 in addition to CYP2C8. Overall, our results demonstrate for the first time that desloratadine glucuronidation by UGT2B10 followed by CYP2C8 oxidation and a deconjugation event are responsible for the formation of 3-hydroxydesloratadine.

H1-antihistamines for chronic spontaneous urticaria

Background Chronic spontaneous urticaria (CSU) is characterised by the development of crops of red, itchy, raised weals or hives with no identifiable external cause.Objectives To assess the effects of H1-antihistamines for CSU.Search methods We searched the following databases up to June 2014: Cochrane Skin Group Specialised Register, CENTRAL (2014, Issue 5), MEDLINE(from 1946), EMBASE (from 1974) and PsycINFO (from 1806). We searched five trials registers and checked articles for references to relevant randomised controlled trials.Selection criteria We included randomised controlled trials of H1-antihistamines for CSU. Interventions included single therapy or a combination of H1-antihistamines compared with no treatment (placebo) or another active pharmacological compound at any dose.Data collection and analysis We used standard methodological procedures as expected by The Cochrane Collaboration.Our primary outcome measures were proportion of participants with complete suppression of urticaria: 'good or excellent' response,50% or greater improvement in quality of life measures, and adverse events.We present risk ratios (RR) with 95% confidence intervals(CIs). Main results We identified 73 studies (9759 participants); 34 studies provided data for 23 comparisons. The duration of the intervention was up to two weeks (short-term) or longer than two weeks and up to three months (intermediate-term).Cetirizine 10mg once daily in the short term and in the intermediate term led to complete suppression of urticaria by more participants than was seen with placebo (RR 2.72, 95% CI 1.51 to 4.91). For this same outcome, comparison of desloratadine versus placebo in the intermediate term (5 mg) (RR 37.00, 95% CI 2.31 to 593.70) and in the short term (20 mg) (RR 15.97, 95% CI 1.04 to 245.04)favoured desloratadine, but no differences were seen between 5 mg and 10 mg for short-term treatment.Levocetirizine 20 mg per day (short-term) was more effective for complete suppression of urticaria compared with placebo (RR 20.87,95% CI 1.37 to 317.60), and at 5 mg was effective in the intermediate term (RR 52.88, 95% CI 3.31 to 843.81) but not in the shortterm, nor was 10 mg effective in the short term.Rupatadine at 10 mg and 20 mg in the intermediate term achieved a 'good or excellent response' compared with placebo (RR 1.35,95% CI 1.03 to 1.77).Loratadine (10 mg) versus placebo (RR 1.86, 95% CI 0.91 to 3.79) and loratadine (10 mg) versus cetirizine (10 mg) (RR 1.05, 95%CI 0.76 to 1.43) over short-term and intermediate-term treatment showed no significant difference for 'good or excellent response' or for complete suppression of urticaria, respectively.Loratadine (10 mg) versus desloratadine (5 mg) (intermediate-term) showed no statistically significant difference for complete suppression of urticaria (RR 0.91, 95% CI 0.78 to 1.06) or for 'good or excellent response' (RR 1.04, 95% CI 0.64 to 1.71). For loratadine(10 mg) versus mizolastine (10 mg) (intermediate-term), no statistically significant difference was seen for complete suppression of urticaria (RR 0.86, 95% CI 0.64 to 1.16) or for 'good or excellent response' (RR 0.88, 95% CI 0.55 to 1.42).Loratadine (10mg) versus emedastine (2mg) (intermediate-term) showed no statistically significant difference for complete suppression(RR 1.04, 95% CI 0.78 to 1.39) or for 'good or excellent response' (RR 1.09, 95% CI 0.96 to 1.24); the quality of the evidence was moderate for this comparison.No difference in short-term treatment was noted between loratadine (10mg) and hydroxyzine (25mg) in terms of complete suppression(RR 1.00, 95% CI 0.32 to 3.10).When desloratadine (5 to 20 mg) was compared with levocetirizine (5 to 20 mg), levocetirizine appeared to be the more effective (P value < 0.02).In a comparison of fexofenadine versus cetirizine, more participants in the cetirizine group showed complete suppression of urticaria(P value < 0.001).Adverse events leading to withdrawals were not significantly different in the following comparisons: cetirizine versus placebo at 10 mg and 20 mg (RR 3.00, 95% CI 0.68 to 13.22); desloratadine 5 mg versus placebo (RR 1.46, 95% CI 0.42 to 5.10); loratadine 10 mg versus mizolastine 10 mg (RR 0.38, 95% CI 0.04 to 3.60); loratadine 10mg versus emedastine 2mg (RR 1.09, 95%CI 0.07 to 17.14);cetirizine 10 mg versus hydroxyzine 25 mg (RR 0.78, 95% CI 0.25 to 2.45); and hydroxyzine 25 mg versus placebo (RR 3.64, 95%CI 0.77 to 17.23), all intermediate term.No difference was seen between loratadine 10 mg versus mizolastine 10 mg in the proportion of participants with at least 50%improvement in quality of life (RR 3.21, 95% CI 0.32 to 32.33).Authors' conclusions Although the results of our review indicate that at standard doses of treatment, several antihistamines are effective when compared with placebo, all results were gathered from a few studies or, in some cases, from single-study estimates. The quality of the evidence was affected by the small number of studies in each comparison and the small sample size for many of the outcomes, prompting us to downgrade the quality of evidence for imprecision (unless stated for each comparison, the quality of the evidence was low).No single H1-antihistamine stands out as most effective. Cetirizine at 10 mg once daily in the short term and in the intermediate term was found to be effective in completely suppressing urticaria. Evidence is limited for desloratadine given at 5 mg once daily in the intermediate term and at 20 mg in the short term. Levocetirizine at 5 mg in the intermediate but not short term was effective for complete suppression. Levocetirizine 20 mg was effective in the short term, but 10 mg was not. No difference in rates of withdrawal due to adverse events was noted between active and placebo groups. Evidence for improvement in quality of life was insufficient.

Population pharmacokinetic analysis of fexofenadine in Japanese pediatric patients

A population pharmacokinetic analysis was conducted to characterize the pharmacokinetics of fexofenadine in Japanese pediatric patients (6 months through 16 years) with perennial allergic rhinitis or atopic dermatitis. The dataset was composed of 515 patients (including 109 adults), for a total of 1,080 concentration-time points. The analysis was performed with NONMEM using the SAEM method. Several structural models and residual error models were evaluated. The relationship between the individual estimates and the potential covariates was then investigated: demographic and pathophysiologic characteristics were tested as potential model covariates (forward selection method). The qualification of the model was performed using visual predictive check and bootstrap. A two-compartment disposition model with first-order absorption best fitted the data. The inter-individual variability was modeled through an exponential error model for all parameters (except for ka for which no inter-individual term could be estimated), while a proportional error model was used to model the residual variability. The final model included two covariates on elimination clearance and one on the intercompartmental clearance. CL/F was related to BSA and patient's age (expressed in months) Q/F was also related to BSA. Once the model was correctly qualified, exposure parameters such as Cmax and AUCτ were computed and compared between each age sub-group and between Japanese and Caucasians patients. These comparisons did not reveal any major difference (less than 50 %) between subgroups.

Comparison of levocetirizine pharmacokinetics after single doses of levocetirizine oral solution and cetirizine dry syrup in healthy Japanese male subjects

Objective

Levocetirizine, the R-enantiomer of cetirizine, is classified as a second generation antihistamine used for the treatment of allergic disorders. This study aimed to compare exposure to levocetirizine when given as levocetirizine oral solution (OS) 5 mg to that when given as cetirizine dry syrup (DS) 10 mg, which contains equal proportions of levocetirizine and dextrocetirizine, in healthy Japanese male subjects.

Methods

The study was conducted in an open-label, single dose, randomized and two-way cross-over design. Eligible subjects were allocated to one of two groups and received either levocetirizine OS 5 mg or cetirizine DS 10 mg under fasting conditions, and the alternate treatment after a 7-days washout period. Serial blood samples were taken after each administration, and plasma levocetirizine concentrations were determined using a validated LC-MS/MS method. Pharmacokinetic parameters were calculated by using non-compartmental analysis. Comparisons of levocetirizine pharmacokinetics were conducted with maximum concentration (C_max) and the area under the plasma concentration-time curve from dosing until 48 h post-dose (AUC_0–48) after each treatment.

Clinical Trial registration number

ClinicalTrials.gov identifier is NCT01622283

Results

The mean C_max and AUC_0–48 of levocetirizine after a single dose of levocetirizine OS 5 mg and cetirizine DS 10 mg were 203.3 ± 42.49 ng/mL and 1814.9 ± 304.22 ng.hr/mL, and 196.5 ± 31.31 ng/mL and 1710.5 ± 263.31 ng hr/mL, respectively. The ratios and the 90% CIs of the geometric least squares means ratios of C_max and AUC_0–48 were 1.027 (0.968–1.091) and 1.059 (1.024–1.094), respectively.

Limitation

The small sample size and single dose design of this study prevent definitive conclusions regarding the pharmacokinetics and safety of levocetirizine OS in a Japanese patient population being made. Study limitations include conducting the study in adult males, not in children.

Conclusions

Levocetirizine exposure in plasma was equivalent when given as levocetirizine OS 5 mg and as cetirizine DS 10 mg. Both preparations were safe and well-tolerated in healthy Japanese male subjects.

Pharmacology of antihistamines

H1-antihistamines, the mainstay of treatment for urticaria, were developed from anticholinergic drugs more than 70 years ago. They act as inverse agonists rather than antagonists of histamine H1-receptors which are members of the G-protein family. The older first generation H1-antihistamines penetrate readily into the brain to cause sedation, drowsiness, fatigue and impaired concentration and memory causing detrimental effects on learning and examination performance in children and on impairment of the ability of adults to work and drive. Their use should be discouraged. The newer second-generation H1-antihistamines are safer, cause less sedation and are more efficacious. Three drugs widely used for symptomatic relief in urticaria, desloratadine, levocetirizine and fexofenadine are highlighted in this review. Of these levocetirizine and fexofenadine are the most potent in humans in vivo. However, levocetirizine may cause somnolence in susceptible individuals, whereas fexofenadine has a relatively short duration of action and may be required to be given twice daily for all round daily protection. Although desloratadine is less potent, it has the advantages of rarely causing somnolence and having a long duration of action.

Safety evaluation of desloratadine in allergic rhinitis

INTRODUCTION

Desloratadine is a biologically active metabolite of second-generation antihistamine loratadine. It is also indicated for the treatment of allergic diseases, including allergic rhinitis.

AREAS COVERED

A Medline search was conducted to identify preclinical and clinical studies of desloratadine. This was supplemented with additional articles obtained from online sources. The focus of this review is on the safety profile of desloratadine.

EXPERT OPINION

The review of these data indicates that the safety profile of desloratadine is similar to other second-generation antihistamines. Desloratadine is highly selective for histamine H₁-receptors, does not cross the blood-brain barrier (BBB), and has minimal adverse events (very low sedation rate), with a better safety and tolerability than first-generation antihistamines. Desloratadine is safe and well tolerated without having central nervous system (CNS) or cardiovascular effects and with low drug interaction.

Pharmacology of antihistamines

This article reviews the molecular biology of the interaction of histamine with its H1-receptor and describes the concept that H1-antihistamines are not receptor antagonists but are inverse agonists i.e. they produce the opposite effect on the receptor to histamine. It then discourages the use of first-generation H1-antihistamines in clinical practice today for two main reasons. First, they are less effective than second generation H1-antihistamines. Second, they have unwanted side effects, particularly central nervous system and anti-cholinergic effects, and have the potential for causing severe toxic reactions which are not shared by second-generation H1-antihistamines. There are many efficacious and safe second-generation H1-antihistamines on the market for the treatment of allergic disease. Of the three drugs highlighted in this review, levocetirizine and fexofenadine are the most efficacious in humans in vivo. However, levocetirizine may cause somnolence in susceptible individuals while fexofenadine has a relatively short duration of action requiring twice daily administration for full all round daily protection. While desloratadine is less efficacious, it has the advantages of rarely causing somnolence and having a long duration of action. Lastly, all H1-antihistamines have anti-inflammatory effects but it requires regular daily dosing rather than dosing 'on-demand' for this effect to be clinically demonstrable.

Pharmacology of antihistamines

This article reviews the molecular biology of the interaction of histamine with its H₁-receptor and describes the concept that H₁-antihistamines are not receptor antagonists but are inverse agonists i.e. they produce the opposite effect on the receptor to histamine. It then discourages the use of first-generation H₁-antihistamines in clinical practice today for two main reasons. First, they are less effective than second generation H₁-antihistamines. Second, they have unwanted side effects, particularly central nervous system and anti-cholinergic effects, and have the potential for causing severe toxic reactions which are not shared by second-generation H₁-antihistamines. There are many efficacious and safe second-generation H₁-antihistamines on the market for the treatment of allergic disease. Of the three drugs highlighted in this review, levocetirizine and fexofenadine are the most efficacious in humans in vivo. However, levocetirizine may cause somnolence in susceptible individuals while fexofenadine has a relatively short duration of action requiring twice daily administration for full all round daily protection. While desloratadine is less efficacious, it has the advantages of rarely causing somnolence and having a long duration of action. Lastly, all H₁-antihistamines have anti-inflammatory effects but it requires regular daily dosing rather than dosing 'on-demand' for this effect to be clinically demonstrable.

The impact of P-glycoprotein mediated efflux on absorption of 11 sedating and less-sedating antihistamines using Caco-2 monolayers

Caco-2 cells were used to compare P-gp mediated efflux and passive permeability using bidirectional transport of 11 antihistamines. An efflux ratio >2 indicated active efflux, with PSC833 and GF120918 used as functional P-gp inhibitors. Antihistamines were measured directly by HPLC or LC/MS. Fexofenadine had an efflux ratio of 37, yet had negligible passive permeability, even in the presence of a pH gradient (0.1 × 10(-6) cm/sec). Its precursor, terfenadine, had an efflux ratio of 2.5, while cetirizine, desloratadine and hydroxyzine were 4, 7 and 14, respectively. After incubation with P-gp inhibitors, these ratios dropped significantly. Loratadine, by contrast, had equivalent transport in both directions and passive permeability was high (24 × 10(-6) cm/sec). Dimenhydrinate was the only other sedating antihistamine to exhibit efflux, with a ratio of 10. Gradient conditions of pH (6/7.4) increased efflux of terfenadine and desloratadine to over 31 and 38 fold respectively, yet this increased efflux was not associated with P-gp. Altering functional P-gp in the gut is likely to influence absorption of some sedating antihistamines such as dimenhydrinate and hydroxyzine and most less-sedating antihistamines except loratadine. In addition, desloratadine exhibits pH dependent efflux which could further induce variable absorption of this antihistamine.

H1-antihistamine up-dosing in chronic spontaneous urticaria: patients' perspective of effectiveness and side effects--a retrospective survey study

BACKGROUND

The guidelines recommend that first line treatment of chronic spontaneous urticaria should be second generation non-sedating H(1)-antihistamines with a positive recommendation against the use of old sedating first generation antihistamines. If standard dosing is not effective, increasing the dosage up to four-fold is recommended. The objective of this study was to obtain the chronic spontaneous urticaria-patient perspective on the effectiveness and unwanted effects of H(1)-antihistamines in standard and higher doses.

METHODOLOGY/PRINCIPAL FINDINGS

This was a questionnaire based survey, initially completed by 368 individuals. 319 (248 female, 71 male, median age 42 years) had a physician-confirmed diagnosis of chronic spontaneous urticaria and were included in the results. Participants believed standard doses (manufacturers recommended dose) of second generation antihistamines to be significantly (P<0.005) more effective than first generation drugs. Furthermore, they believed that second generation drugs caused significantly (P<0.001) fewer unwanted effects and caused significantly (P<0.001) less sedation than first generation antihistamines. Three-quarters of the patients stated that they had up-dosed with antihistamines with 40%, 42% and 54% reporting significant added benefit from taking 2, 3 or 4 tablets daily respectively. The number of reports of unwanted effects and sedation following up-dosing were not significantly different from those reported for standard doses.

CONCLUSIONS

This survey supports the urticaria guidelines recommendations that the first line treatment for chronic spontaneous urticaria should be second generation rather than first generation H(1)-antihistamines and that, if standard dosing is not effective, the dosage should be increased up to four-fold.

Mast cell activation by fibrinogen-related homologous c-terminal peptides (haptides) modulates systemic blood pressure

BACKGROUND

Haptides are a family of short peptides homologous to C-termini sequences of fibrinogen chains β and γ (haptides Cβ and preCγ, respectively) which were previously shown to penetrate and bind cells.

OBJECTIVES

This work investigates the systemic effect of the haptides with possible clinical implications.

METHODS

Intra-arterial monitoring in rats recorded the haptides' effects on systemic blood pressure. In parallel, their effect was also tested in vitro on isolated rat peritoneal mast cells and on human mast cells.

RESULTS

Intra-arterial monitoring in rats showed that intravenous administration of low haptides concentrations (35-560 μg/kg rat) caused a shocklike behavior with transient decrease in the systolic and diastolic blood pressure by up to 55% (P < .05) in a dose-dependent manner and a minor increase in their heart rate. Randomly scrambled sequences of the haptides had no such effect, suggesting a specific interaction with receptors. Intravenous administration of blockers to histamine receptors H1 and H2 before haptides administration attenuated this effect. Furthermore, in vitro incubation of human LAD2 mast cell line or isolated rat peritoneal mast cells with the haptides caused degranulation of the mast cells. We found that the haptides Cβ and preCγ activated mast cells causing histamine release, resulting in a steep decrease in blood pressure, comparable to anaphylactic shock.

CONCLUSION

In treating vascular occlusive diseases, massive fibrinolysis is induced, and haptide-containing sequences are released. We suggest that treatment with histamine receptor blockers or with mast cell stabilizing agents in such pathological conditions may overcome this effect.