Efficacy and safety of loratadine (10 mg once daily), terfenadine (60 mg twice daily), and placebo in the treatment of seasonal allergic rhinitis

Diphenhydramine: Time to Move on?

Diphenhydramine is one of the most widely available, longest-used antihistamine medications but has many side effects including sedation and risk of toxicity in overdose including cardiac toxicity. It is frequently inappropriately used when newer, more favorable antihistamine medications are available. Second-generation antihistamines are also widely available and affordable, with many of the same desired effects as diphenhydramine and fewer, if any, of the undesirable side effects. Because of the negative side effects and wide availability of alternative antihistamine medications, it is definitively time to move on from diphenhydramine.

Onset of action for loratadine tablets for the symptomatic control of seasonal allergic rhinitis in adults challenged with ragweed pollen in the Environmental Exposure Unit: a post hoc analysis of total symptom score

Background

Loratadine is a second-generation, non-sedating antihistamine used for the relief of allergic rhinitis symptoms. Previous studies reported that when loratadine was encapsulated, the onset of action for symptom relief was 180 min. However, unmodified loratadine tablets were not evaluated at that time. Using data from a previously published Environmental Exposure Unit (EEU) study comparing azelastine nasal spray with loratadine tablets, cetirizine tablets, and placebo, this post hoc analysis determines the onset of action of loratadine tablets (i.e. unmodified) by analyzing the total symptom score for the relief of nasal and ocular seasonal allergic rhinitis (SAR) symptoms.

Methods

A Phase IV, randomized, single-center, double-blind, placebo-controlled, double-dummy, four-way crossover study was conducted in the EEU. Seventy participants were randomized sequentially into one of the four treatments during ragweed pollen exposure. Nasal and ocular symptom scores were self-reported by the participants and recorded. The original study analysis was carried out by evaluating the nasal symptom scores only. For this post hoc analysis, both nasal and ocular data from the loratadine and placebo treatment arms were analyzed. The primary endpoint for this analysis was the onset of action of loratadine as measured by the change in total symptom score (TSS) from baseline in comparison to placebo. The onset of ocular symptom relief using the total ocular symptom score (TOSS) was also reported.

Results

Loratadine tablets demonstrated a significant and durable improvement in both TSS (P = .005) and TOSS (P = .013) at 75 min post-treatment administration compared to placebo. The mean proportion of participants reporting none or mild for all component symptoms of TSS and TOSS at 75 min and thereafter was significantly higher in the loratadine (TSS, P = .0005; TOSS, P ≤ .0001) vs. placebo treatment arm.

Conclusions

The onset of action of loratadine tablets was 75 min for the relief of nasal and ocular symptoms in adults with SAR. These results suggest a faster onset of action for loratadine tablets (75 min) compared to previously reported studies which were conducted with modified (i.e. gelatin-encapsulated) loratadine tablets (180 min).

Trial registration Clinicaltrials.gov identifier NCT00561717

Electronic supplementary material

The online version of this article (10.1186/s13223-017-0227-4) contains supplementary material, which is available to authorized users.

Inhibition of the histamine-induced weal and flare response: a valid surrogate measure for antihistamine clinical efficacy?

Histamine plays a central role in allergic responses. Inhibition of the weal and flare response to histamine is a traditional pharmacodynamic tool to measure the activity of H(1)-receptor antagonists. The time course and duration of cutaneous weal and flare inhibition are often used as surrogate measures of clinical efficacy. Pharmacodynamic differences among antihistamines are often interpreted to indicate differences in clinical efficacy. A systematic review of literature from 1980 to 2006 regarding the histamine induced weal and flare was undertaken. Search terms included 'histamine', 'skin test', 'weal', 'flare', and 'antihistamine'; retrieved articles were searched for relevant studies not identified initially. Data from human studies on the inhibition of the weal and flare by second-generation antihistamines were extracted and assessed. A literature search from 1980 to 2006 was undertaken for comparative studies of second-generation antihistamines in the clinical settings of allergic rhinitis (AR) and chronic idiopathic urticaria; data extracted from these studies underwent systematic review. Differences were noted among second-generation antihistamines in terms of their ability to inhibit the histamine-induced weal and flare. Corresponding differences in terms of clinical efficacy in AR and chronic urticaria were not identified following a systematic review. The reasons for the disconnect between pharmacodynamic effects and clinical efficacy may include differences between the route and concentration of histamine, the involvement of mediators other than histamine in the allergic response, and the short time course of pharmacodynamic studies. The histamine-induced weal and flare response is a pharmacodynamic test that should not be used to compare the clinical efficacy of different antihistamines, and is not an adequate alternative to clinical end-point assessments in AR or chronic idiopathic urticaria.

The economic impact of payer policies after the Rx-to-OTC switch of second-generation antihistamines

OBJECTIVE

As a result of the over-the-counter (OTC) introduction of loratadine, health plans have been struggling to determine the best policy to incorporate this change within their existing drug benefit structure for second-generation antihistamines (SGA). The objective of this study was to examine the economic impact of payer policies in response to the Rx-to-OTC switch of loratadine.

STUDY DESIGN

Decision analysis was used to model the budgetary impact and cost-effectiveness of four policies for SGA benefits for the managed care organization (MCO), employer, and Medicaid perspectives separately.

PATIENTS AND METHODS

Outcomes included direct medical costs and lost productivity (employers only), discounted, quality-adjusted life-years (QALYs) saved because of amelioration of allergic rhinitis symptoms and avoidance of unintentional injuries associated with the use of first-generation antihistamines (FGA). Bayesian probabilistic sensitivity analysis was conducted using second-order Monte Carlo simulation.

RESULTS

Providing limited OTC and second-tier prescription benefits would cost approximately 0.13 dollars and 0.30 dollars compared to third-tier prescription benefits for employers and MCOs, respectively, and would save Medicaid 0.02 dollars per member per month (PMPM). Providing limited coverage for OTC loratadine while retaining second-tier prescription benefits for SGA was the optimal policy for a willingness to pay below 26,200 dollars per QALY for all payers.

CONCLUSIONS

Offering second-tier prescription and limited OTC benefits provides greater effectiveness and is not significantly more expensive PMPM than discontinuation. Some of the drug savings from limiting coverage of prescription SGA may be attenuated by the cost of lost productivity and direct medical expenditures due to unintentional injuries associated with increased FGA use in addition to the increased cost of therapeutic substitutes.

Transitioning the Second-Generation Antihistamines to Over-the-Counter Status

BACKGROUND

A U.S. Food and Drug Administration advisory committee deemed the second-generation antihistamines (SGA) safe for over-the-counter use against the preliminary opposition of the manufacturers. As a result, loratadine is now available over-the-counter. First-generation antihistamines (FGA) are associated with an increased risk of unintentional injuries, fatalities, and reduced productivity. Access to SGA over-the-counter could result in decreased use of FGA, thereby reducing deleterious outcomes. The societal impact of transitioning this class of medications from prescription to over-the-counter status has important policy implications.

OBJECTIVE

To examine the cost-effectiveness of transitioning SGA to over-the-counter status from a societal perspective.

RESEARCH DESIGN

A simulation model of the decision to transition SGA to over-the-counter status was compared with retaining prescription-only status for a hypothetical cohort of individuals with allergic rhinitis in the United States. Estimates of costs and effectiveness were obtained from the medical literature and national surveys. Sensitivity analysis was performed using a second-order Monte Carlo simulation.

MAIN OUTCOME MEASURES

Discounted, quality-adjusted life-years saved as a result of amelioration of allergic rhinitis symptoms and avoidance of motor vehicle, occupational, public and home injuries and fatalities; discounted direct and indirect costs.

RESULTS

Availability of SGA over-the-counter was associated with annual savings of 4 billion dollars (2.4-5.3 billion dollars) or 100 dollars (64-137 dollars) per allergic rhinitis sufferer and 135,061 time-discounted quality-adjusted life years (84,913-191,802). The sensitivity analysis provides evidence in support of these results.

CONCLUSION

Making SGA available over-the-counter is both cost-saving and more effective for society, largely as a result of reduced adverse outcomes associated with FGA-induced sedation. Further study is needed to determine the differential impact on specific vulnerable populations.

Montelukast for treating seasonal allergic rhinitis: a randomized, double-blind, placebo-controlled trial performed in the spring

BACKGROUND

Cysteinyl leukotrienes are important proinflammatory mediators believed to have a role in allergic rhinitis.

OBJECTIVE

This multicentre, randomized, double-blind, placebo- and active-controlled trial evaluated the effectiveness and tolerability of montelukast, a cysteinyl leukotriene receptor antagonist, for treating patients with seasonal allergic rhinitis.

METHODS

After a 3- to 5-day, single-blind placebo run-in period, 1302 male and female patients (aged 15-81 years) with active allergic rhinitis symptoms were randomly assigned to receive montelukast 10 mg (n = 348), loratadine 10 mg (n = 602), or placebo (n = 352) administered once daily at bedtime for 2 weeks during the spring allergy season.

RESULTS

Mean patient characteristics and symptom scores at baseline were similar for the three treatment groups. The primary end-point, daytime nasal symptoms score (mean of nasal congestion, rhinorrhea, nasal pruritus, and sneezing scores; 0-3 scale), improved from baseline during treatment by (least squares mean, 95% confidence interval) - 0.37 (- 0.43, - 0.31), - 0.47 (- 0.52, - 0.43), and - 0.24 (- 0.29, - 0.18) in the montelukast, loratadine, and placebo groups, respectively (P < or = 0.001 comparing each active treatment with placebo). Mean changes from baseline in all other diary-based scores, including night-time and eye symptom scores, were significantly greater for each active treatment than for placebo. The rhinoconjunctivitis quality of life overall score improved significantly with montelukast and with loratadine as compared with placebo. Montelukast and loratadine showed a safety profile comparable to that of placebo.

CONCLUSION

Montelukast is well tolerated and provides improvements in daytime and night-time symptoms, as well as quality of life parameters, for patients with seasonal allergic rhinitis.

The added benefit of local Patanol therapy when combined with systemic Claritin for the inhibition of ocular itching in the conjunctival antigen challenge model

BACKGROUND

Allergic conjunctivitis very often occurs simultaneously with rhinitis in seasonal allergy sufferers. While systemic anti-allergic and antihistaminic agents are effective against many signs and symptoms of allergy, they may not adequately control ocular signs and symptoms in patients with multiple target organ hypersensitivity. Patanol (olopatadine hydrochloride 0.1% ophthalmic solution, Alcon Laboratories, Inc., Fort Worth, TX), a new effective anti-allergic mast cell stabilizer with antihistaminic properties, is approved for the prevention of ocular itching due to allergic conjunctivitis.

OBJECTIVE

To determine whether Patanol in combination with the systemic antihistamine Claritin (loratadine, Schering, Kenilworth, NJ) reduces the ocular itching associated with allergic conjunctivitis more effectively than Claritin alone. A topical ocular antigen challenge induced the allergic conjunctivitis in 15 subjects.

METHODS

This was a randomized, double-masked study in which the contralateral eye served as the control. On Visit 1, an allergen dose which elicited response scores > 2 for ocular itching was identified. Itching was graded by the subject using a 0 to 4 point scale. At Visit 2, the threshold allergen concentration was confirmed. At Visit 3, the onset of action challenge, in addition to Claritin (10 mg tablet), each subject received Patanol in one eye and placebo in the fellow eye in a randomized, double-masked fashion. Allergen was instilled one hour after dosing, and ocular itching was graded at 3, 7, 10 and 20 minutes after challenge. At Visit 4, the duration of action challenge, the same drug regimen was followed as in Visit 3. However, allergen challenge was performed eight hours after dosing, and itching graded after 3, 7, 10 and 20 minutes.

RESULTS

Patient eyes treated with Patanol were significantly less itchy than those treated with systemic Claritin alone at critical time points 3, 7, and 10 minutes after the onset of action challenge (p < 0.05), and at 3 and 7 minutes after the duration of action challenge (p < 0.05).

CONCLUSION

The addition of topical Patanol to systemic Claritin therapy significantly reduced ocular itching associated with allergic conjunctivitis compared to treatment with Claritin alone. These findings prove the added benefit of local Patanol therapy in the treatment of ocular allergic symptoms in patients receiving systemic antihistamines for concomitant systemic allergies.

Triamcinolone acetonide aqueous nasal spray versus loratadine in seasonal allergic rhinitis: efficacy and quality of life

BACKGROUND

The new aqueous formulation of triamcinolone acetonide (TAA) was compared with loratadine in patients with seasonal allergic rhinitis.

OBJECTIVE

The primary objective of the study was to compare the safety and efficacy of TAA aqueous with loratadine in relieving the symptoms of seasonal allergic rhinitis.

METHODS

A total of 351 patients were enrolled into this 4-week, double-blind, double-dummy, randomized, parallel group study. Patients received either TAA aqueous nasal spray (220 microg) or loratadine (10 mg) once daily. Efficacy variables were rhinitis symptom changes from baseline, physician global evaluations, and the patient dropout rate due to insufficient treatment effect. Safety and quality of life also was evaluated.

RESULTS

Both TAA aqueous-treated and loratadine-treated patients had improvement in symptoms as early as day 1. Overall, TAA aqueous was significantly (P < .05) more effective than loratadine in reducing total nasal symptoms and individual symptoms of nasal congestion, nasal itch, and sneezing. Ocular symptoms improved from baseline in both groups. There was no statistically significant difference between groups based on physician global evaluation. A similar number of patients in each group discontinued the study due to ineffective treatment. Triamcinolone acetonide aqueous patients maintained a significantly (P < .05) better quality of life in three of the dimensions (activity, nasal symptoms, and practical problems) and for overall quality of life. There were no differences between the two treatment groups in the incidence of adverse events, none of which were clinically significant.

CONCLUSIONS

Both TAA aqueous and loratadine were effective and well-tolerated in the treatment of patients with seasonal allergic rhinitis. Triamcinolone acetonide aqueous was significantly (P < .05) more effective than loratadine in controlling nasal symptoms of seasonal allergic rhinitis and maintaining a better quality of life for the patients.

Onset-of-action for antihistamine and decongestant combinations during an outdoor challenge

BACKGROUND

Medications containing a combination antihistamine-decongestant are commonly used for allergic rhinitis yet onset-of-action comparisons for symptom relief after a single dose have not been performed.

OBJECTIVE

To determine the onset of symptom relief and efficacy of antihistamine-decongestant medications (acrivastine-pseudoephedrine and loratadine-pseudoephedrine) compared with placebo in an outdoor park.

METHODS

This study was conducted during the spring of 1997 using a double-blind, placebo-controlled design. Patients completed baseline rhinitis symptom diaries from 7:30 to 9:30 AM. Subjects with qualifying symptom scores received one dose of either acrivastine-pseudoephedrine, loratadine-pseudoephedrine, or placebo at 10:00 AM. Symptom diaries were recorded for the next 4 hours.

RESULTS

Of 593 patients randomized to treatment, 592 were included in efficacy analysis. Acrivastine-pseudoephedrine and loratadine-pseudoephedrine demonstrated a mean onset-of-action by 45 and 30 minutes respectively for total symptom and rhinitis symptom scores for the five sites. Onset-of-action for nasal congestion scores was 45 minutes for both medications. Sites having higher pollen exposure (>100 pollen grains over 6 hours) demonstrated a difference between the antihistamine combinations: acrivastine-pseudoephedrine had an onset of action at 45 minutes for total symptom and rhinitis symptom scores, and 15 minutes for nasal congestion scores whereas loratadine-pseudoephedrine had onset-of-action for nasal congestion score of 105 minutes but failed to reach significance at any timepoint for total symptom and rhinitis symptom scores.

CONCLUSIONS

Both antihistamine-decongestant combinations demonstrate an onset-of-action within 60 minutes of administration but under conditions of higher pollen exposure, the acrivastine combination was more effective for total symptoms, rhinitis symptoms, and nasal congestion with an onset-of-action within 45 minutes for rhinitis symptoms and 15 minutes for congestion.

Lack of effect of terfenadine on the pharmacokinetics of the CYP3A4 substrate buspirone

The effects of terfenadine, a non-sedating antihistamine on the pharmacokinetics and pharmacodynamics of buspirone, a CYP3A4 substrate, were investigated in a randomised, placebo-controlled, two-phase cross-over study. Ten healthy volunteers took either 120 mg terfenadine or matched placebo orally once daily for 3 days. On day 3, 10 mg buspirone was taken orally. Plasma concentrations of buspirone were measured up to 18 hr and its pharmacodynamic effects up to 8 hr. Terfenadine slightly but not significantly increased plasma concentrations of buspirone. No psychomotor deterioration was observed during the terfenadine phase. In conclusion, terfenadine did not significantly affect the pharmacokinetics of buspirone, a CYP3A4 substrate shown to be very susceptible to interactions with CYP3A4 inhibitors. Thus, terfenadine is expected to have little effect on the pharmacokinetics of CYP3A4 substrates in general.

Second-generation antihistamines: a comparative review

Second-generation histamine H1 receptor antagonists (antihistamines) have been developed to reduce or eliminate the sedation and anticholinergic adverse effects that occur with older H1 receptor antagonists. This article evaluates second-generation antihistamines, including acrivastine, astemizole, azelastine, cetirizine, ebastine, fexofenadine, ketotifen, loratadine, mizolastine and terfenadine, for significant features that affect choice. In addition to their primary mechanism of antagonising histamine at the H1 receptor, these agents may act on other mediators of the allergic reaction. However, the clinical significance of activity beyond that mediated by histamine H1 receptor antagonism has yet to be demonstrated. Most of the agents reviewed are metabolised by the liver to active metabolites that play a significant role in their effect. Conditions that result in accumulation of astemizole, ebastine and terfenadine may prolong the QT interval and result in torsade de pointes. The remaining agents reviewed do not appear to have this risk. For allergic rhinitis, all agents are effective and the choice should be based on other factors. For urticaria, cetirizine and mizolastine demonstrate superior suppression of wheal and flare at the dosages recommended by the manufacturer. For atopic dermatitis, as adjunctive therapy to reduce pruritus, cetirizine, ketotifen and loratadine demonstrate efficacy. Although current evidence does not suggest a primary role for these agents in the management of asthma, it does support their use for asthmatic patients when there is coexisting allergic rhinitis, dermatitis or urticaria.

Rapid and sustained efficacy of mizolastine 10 mg once daily in seasonal allergic rhinitis

This 28-day, double-blind, randomized study in 256 patients compared the efficacy and safety of mizolastine 10 mg daily with placebo in patients with seasonal allergic rhinoconjunctivitis. All four nasal symptoms (itch, rhinorrhoea, sneezing, obstruction) and three ocular symptoms (itch, tears, redness) were rated by investigators using both a 0-3 and a 0-9 rating scale. Compared with the placebo group total, nasal and ocular scores were all significantly lower in the mizolastine-treated patients at day 14 of the study (P = 0.0002-0.0009, using the 0-9 scale) and relief was maintained throughout the 4-week study duration. Patient diary total scores showed that mizolastine was effective from the first day of treatment. The 0-9 scale appears to be more sensitive than the 0-3 scale for rating symptoms of seasonal allergic rhinitis.

Changes in skin-test reactivity do not correlate with clinical efficacy of H1-blockers in seasonal allergic rhinitis

New-generation H1-blockers may possess antiallergic properties, and their effect may differ, depending on the target organ. A double-blind, placebo-controlled, parallel-group study was carried out during the pollen season to compare the clinical effect on nasal and conjunctival symptoms of astemizole (10 mg o.d.) and loratadine (10 mg o.d.) with their effect on skin-test reactivity to allergen and histamine. Thirty-eight patients (12-56 years of age) were studied. Nasal and ocular symptoms were recorded daily from days 4 to 7. Skin prick tests with serial concentrations of allergens and one concentration of histamine were carried out before and at the end of the 7-day treatment period. Parallel-line bioassay, analysis of variance, and covariance were used to analyze skin test data. Loratadine and astemizole significantly decreased symptoms from baseline (P < 0.004 and P < 0.006). Skin-test reactivity to allergen and histamine was more profoundly decreased by astemizole than loratadine. The histamine covariant was more important in the allergen effect of astemizole than in that of loratadine. Two H1-blockers having the same clinical effect on nasal and ocular symptoms during the pollen season have totally different effects on skin-test reactivity. Skin-test reactivity to allergen or histamine is not predictive of the clinical efficacy of H1-blockers during seasonal allergic rhinitis.

Brompheniramine, loratadine, and placebo in allergic rhinitis: a placebo-controlled comparative clinical trial

A double-blind, randomized, placebo-controlled, parallel-group, multicenter study was conducted to compare the effectiveness of an extended-release formulation of a classical antihistamine, brompheniramine, and a second-generation compound, loratadine, in the treatment of allergic rhinitis. Subjects with symptoms of allergic rhinitis received brompheniramine 12 mg twice daily (n = 112), loratadine 10 mg once daily (n = 112), or placebo twice daily (n = 114) for 7 days. Study medications were blinded using a double-dummy technique. Subjects completed an overall evaluation of symptom relief on a daily basis and returned on treatment days 3 and 7, at which times the investigator assessed symptom severity. The investigator and subject each completed a global efficacy evaluation, and subjects were interviewed regarding adverse experiences. The primary efficacy variable was the physicians' global efficacy evaluation on day 3. Symptoms also were analyzed as summed severity scores for all symptoms and for the nasal symptom cluster of rhinorrhea, sneezing, and nasal blockage. At all post-baseline evaluations (days 3, 7, and averaged over the two days), brompheniramine was significantly better than loratadine and placebo for both sets of summed symptom scores and all three global assessments. Loratadine was significantly better than placebo for physician ratings of total symptom severity averaged over the two days and for the physician and subject ratings of the nasal cluster on day 3. Central nervous system-related symptoms were the most frequently reported adverse experiences; somnolence was reported most frequently by patients taking brompheniramine, and its occurrence was less frequent as treatment continued. A nonprescription, extended-release formulation of brompheniramine 12 mg twice daily provided significantly better relief of symptomatic allergic rhinitis than loratadine 10 mg once daily.

Pharmacokinetics of loratadine and pseudoephedrine following single and multiple doses of once- versus twice-daily combination tablet formulations in healthy adult males

The pharmacokinetic profiles of single and multiple doses of loratadine, descarboethoxyloratadine (DCL) (the major active metabolite of loratadine), and pseudoephedrine were determined in a randomized, open-label, two-way crossover study in 24 healthy men. Subjects received a single dose (day 1) and multiple doses (days 3 to 10) of a once-daily (QD) formulation of loratadine 10 mg in an immediate-release coating and pseudoephedrine sulfate 240 mg in an extended-release core (CLAR-ITIN-D 24 HOUR tablets), and a twice-daily (BID) formulation of loratadine 5 mg in an immediate-release coating and pseudoephedrine sulfate 120 mg, with 60 mg in an immediate-release coating and 60 mg in the barrier-protected core (CLARITIN-D 12 HOUR tablets) in study sessions, each separated by a 10-day washout period. Both regimens were safe and well tolerated. On day 1, plasma loratadine, DCL, and pseudoephedrine concentrations were higher following the QD formulation than following the BID formulation, as expected. On day 10, loratadine and DCL maximum plasma concentration (Cmax) values were, on average, 87% and 35% higher, respectively, for the QD formulation than for the BID formulation; however, the values of the area under the plasma concentration-time curve from 0 to 24 hours (AUC0-24) for loratadine and DCL were equivalent (90% confidence interval [CI]: 83% to 110% for loratadine; 90% to 107% for DCL). On day 10, pseudoephedrine Cmax and AUC0-24 values were equivalent (90% CI for Cmax: 94% to 109%; for AUC: 91% to 106%) for the two formulations, and lower pseudoephedrine concentrations were observed from 16 to 24 hours with the QD formulation. Both loratadine/pseudoephedrine formulations produced equivalent loratadine and DCL AUC0-24 values and equivalent pseudoephedrine Cmax and AUC0-24 values following multiple dosing. The lower pseudoephedrine concentrations in the evening with the QD formulation may minimize the potential for insomnia in patients when compared with the BID formulation.

Loratadine in the treatment of urticaria

Urticaria is a common skin disease, which in its chronic form, is a very disturbing condition. Because histamine is the best-documented chemical mediator of urticaria, histamine-antagonists are the mainstay of therapy. First-generation antihistamines are limited by their tendency to produce sedation and anticholinergic side effects. Most of the newer second generation antihistamines compare well with the earlier agents in efficacy but are not limited by the same adverse side effects. Loratadine may be distinguished from other second-generation antihistamines by its pharmacodynamic profile, as well as its tolerability and safety.

Milestones in the biology and pharmacology of H1-receptor antagonists

Daniele Bovet's pioneering discovery that a series of compounds possessing anti-histamine activity reduced the symptoms of anaphylaxis provided the proof that histamine plays a pivotal role as a mediator of allergic reactions. Basophils and mast cells are the major sources of histamine in man and they are thus one of the primary effector cells of allergic inflammation. Some H1-receptor antagonists possess a variety of antiinflammatory activity to H1 antagonism in vitro and in vivo. This promising area should be explored further and much remains to be done in the evaluation of the immunomodulatory effects of anti-histamines.

Highlights in cardiovascular effects of histamine and H1-receptor antagonists

Despite numerous studies, the cardiac actions of histamine are still obscure. Yet, histamine could probably be clinically relevant. It is stored in large amounts in human cardiac tissue, where it is contained in the cytoplasmatic granules of mast cells. Mast cells are present in normal human heart tissue; they are more abundant in diseased human heart tissue where they lie in close proximity to blood vessels and between myocytes. The histamine content of human heart mast cells is comparable to the histamine content of lung parenchymal and skin mast cells. Ultrastructural studies confirmed the presence of mast cells around vessels and between myocytes. Consequently, these cells are easily accessible to circulating antigens, drugs and stimuli that activate the cells to release vasoactive mediators which in turn can exert significant cardiovascular effects. Histamine possesses arrhythmogenic effects and once locally released, may enhance automaticity and induce triggering activity resulting in severe tachyarrhythmias. The major arrhythmogenic effects of histamine consist in increasing sinus rate and ventricular automaticity, and in slowing atrioventricular conduction. In addition, histamine may interfere with depolarization and repolarization through its effects on calcium and potassium currents. These effects are mediated by H2-receptor. Therefore direct activation of histamine receptor can induce cardiac arrhythmias. Consequently, the interference of these histaminergic effects may explain, at least in part, the arrhythmogenic effects described for some second-generation antihistamines, such as terfenadine and astemizole. In this brief review we will discuss the cardiac effects of histamine in experimental animal models and in man, and will review data on the safety of the new second-generation antihistamines, focusing on their cardiotoxic effects.

Influence of food on the oral bioavailability of loratadine and pseudoephedrine from extended-release tablets in healthy volunteers

The effect of a high-fat breakfast on the bioavailability of the components of an extended-release tablet containing 10 mg loratadine in the immediate-release coating and 240 mg pseudoephedrine sulfate in the extended-release core was studied in 24 healthy male volunteers in a single-dose, two-way crossover study. The drug was administered after a 10-hour overnight fast or within 5 minutes of consuming a standardized high-fat breakfast. Serial blood samples were collected over a 48-hour period, and plasma was analyzed for loratadine and its active metabolite descarboethoxyloratadine (DCL), and pseudoephedrine. For pseudoephedrine, maximum concentration (Cmax) and area under the concentration-time curve extrapolated to infinity (AUCzero-infinity) were similar after both treatments, indicating no relevant food effect on the bioavailability of pseudoephedrine. Also, the absorption profiles of pseudoephedrine (from Wagner-Nelson analysis) were similar for the fed and fasted treatments, indicating no apparent differences in absorption. Plasma concentration-time profiles and values for Cmax and AUCzero-infinity of DCL were similar for the two treatments, indicating no relevant food effect on the pharmacokinetics of DCL. In contrast, for loratadine, administration with food resulted in a significantly increased mean Cmax (53%) and AUC from time zero to the final quantifiable sample (AUCif) (76%). However, the resultant Cmax and AUC of loratadine under fed conditions were well below those previously obtained at steady-state after multiple-dose administration of loratadine (40 mg/day) that were shown to be safe and well-tolerated in several clinical studies. The effect of food on the bioavailability and pharmacokinetic profiles of the components of a combination loratadine/pseudoephedrine extended-release tablet is not likely to be clinically significant.

Special considerations in the treatment of seasonal allergic rhinitis in adolescents: the role of antihistamine therapy

The symptoms of seasonal allergic rhinitis often develop during adolescence. Teen-age students with seasonal allergic rhinitis may experience decreased academic performance and productivity from the disease or because of the sedative effects of some antihistamines. The pharmacologic effects of nonsedating second-generation antihistamines are compared with those of classical antihistamines. The effects of antihistamines on sedation and motor and cognitive function are discussed. The role of antiinflammatory agents, decongestants, and combination products is reviewed. Potential drug interactions must be considered along with factors such as drug-induced weight gain and the use of antihistamines in potentially pregnant patients in selecting appropriate antihistamine therapy for adolescent patients.

Efficacy and safety of mizolastine in seasonal allergic rhinitis. The Rhinase Study Group

BACKGROUND

Mizolastine is a new, nonsedating antihistamine under clinical investigation for treatment of allergic rhinitis and urticaria.

OBJECTIVE

The purpose of this study was to determine the optimally active dose of once-daily mizolastine in seasonal allergic rhinitis.

METHODS

This multicenter, double-blind, parallel study involved 494 patients randomly allocated to mizolastine (5, 10, or 15 mg) or placebo for 2 weeks.

RESULTS

Physicians' assessments indicated the superiority of 10 and 15 mg mizolastine to placebo in reducing total symptom scores (P=.002), nasal scores (P=.004), and ocular scores (P=.007) at day 7. Patients' diaries showed a significant change from baseline in daily symptom scores as early as day 2 (P=.01) in 10- and 15-mg mizolastine groups in comparison to placebo, but this was not maintained throughout the study. No additional benefits were demonstrated during the second week of treatment in terms of efficacy. Adverse events were slightly more frequent in the 15-mg mizolastine group.

CONCLUSION

This study conforms mizolastine is an effective and well tolerated antihistamine in the treatment of seasonal allergic rhinitis; 10 mg is the optimal dose.

Loratadine. A reappraisal of its pharmacological properties and therapeutic use in allergic disorders

Loratadine is a long-acting antihistamine agent, exhibiting partial selectivity for peripheral histamine H1-receptors. To date, loratadine has been evaluated in allergic rhinitis, urticaria and, to a limited extent, in asthma. In several large controlled comparative clinical studies, loratadine was superior to placebo, faster acting than astemizole and as effective as azatadine, cetirizine, chlorpheniramine (chlorphenamine), clemastine, hydroxyzine, mequitazine and terfenadine in patients with allergic rhinitis and chronic urticaria. The clinical effectiveness of loratadine in asthma is at present unclear. Loratadine is well tolerated. At dosages of 10 mg daily, commonly reported adverse events were somnolence, fatigue and headache. Sedation occurred less frequently with loratadine than with azatadine, cetirizine, chlorpheniramine, clemastine and mequitazine. Serious ventricular arrhythmias, as reported with some other second generation histamine H1-receptor antagonists, have not been observed with loratadine to date. Thus, loratadine, with its attributes of once daily administration, fast onset of action and essentially nonsedating properties, would appear to be an appropriate first-line agent for the treatment of allergic rhinitis or urticaria.

The pharmacology and use of H1-receptor-antagonist drugs

The second-generation H1-antagonist drugs are supplanting their predecessors in the treatment of allergic rhinoconjunctivitis and chronic urticaria. Their use can be justified mainly on the basis of a more favorable risk-benefit ratio, because they are less toxic to the central nervous system. Future research into H1 antagonists should include additional dose-response studies in patients with allergic disorders, especially children and the elderly; objective studies of adverse effects; studies of topical mucosal application of H1 antagonists; and studies of H1-antagonist enantiomers and active metabolites. With the cloning of the gene encoding the H1 receptor and increased understanding of the precise structural requirements for H1-receptor activity, H1 antagonists with an even more favorable therapeutic index may be developed.

The effect of terfenadine on unilateral nasal challenge with allergen

To investigate the role of H1 receptor-mediated effects in allergic rhinitis, we challenged 12 allergic volunteers with allergen 2 hours after administration of either placebo or 60 mg of terfenadine. Filter paper discs were used for the unilateral administration of allergen and the collection of nasal secretions. Secretion weights, levels of histamine in recovered nasal secretions, and nasal airway resistance (NAR) were measured for each nostril separately, and the number of sneezes was counted. After placebo treatment, allergen challenge led to significant increases in ipsilateral and contralateral secretion weights, ipsilateral histamine levels, ipsilateral NAR, and sneezing. Contralateral histamine levels were not elevated. H1 antagonism with terfenadine markedly reduced the number of sneezes and partially decreased ipsilateral and contralateral secretion weights, without affecting the increase in NAR. Terfenadine premedication also lowered the amount of histamine in ipsilateral secretions after allergen challenge. Performing identical nasal challenges with a 10-fold lower dose of antigen produced similar results. Previous studies showed that terfenadine had no effect on methacholine provocation and completely abolished ipsilateral and contralateral secretion weights after histamine challenge. We conclude that sneezing after allergen challenge is caused almost exclusively by a reflex initiated through H1 receptors and that H1 antagonism has no influence on allergen-induced increases in NAR. Unilateral allergen challenge leads to bilateral increases in secretion weights, which are only partially inhibited by terfenadine, suggesting the involvement of mediators other than histamine in the nasonasal reflex. As reported earlier, terfenadine also decreases allergen-induced histamine release after challenge with the highest dose of antigen.

Loratadine. A review of recent findings in pharmacology, pharmacokinetics, efficacy, and safety, with a look at its use in combination with pseudoephedrine

Antihistamines are considered first-line therapy for the relief of symptoms from allergic rhinitis and chronic urticaria. The newer, second-generation, nonsedating antihistamines reduce the central nervous system and anticholinergic side effects commonly found with previous drugs. The availability of H1-receptor antagonists that produce therapeutic effects without causing unwanted CNS effects fulfills an important practical need, since these drugs are clearly preferable in patients who drive or operate heavy machinery, or who are involved in activities requiring full alertness. Physicians and patients alike are pleased with the efficacy and safety the second-generation antihistamines bring to the treatment of allergy symptoms. Loratadine is an especially effective second-generation H1-receptor antagonist and is comparable to many of the other second-generation antihistamines. Loratadine may be particularly advantageous because of its low dose and the convenience of once-daily dosing. A more subtle advantage, loratadine's antiallergic properties, may warrant its use for specific treatment situations as future research clarifies the nature of the inflammatory response and the mechanisms of action antiallergic antagonists have in this regard.