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PubMed1996

Comparison of triamcinolone acetonide nasal inhaler with astemizole in the treatment of ragweed-induced allergic rhinitis.

BACKGROUND: Few clinical trials have directly compared the efficacy of antihistamines with topical nasal corticosteroids. OBJECTIVE: The study was performed to compare the efficacy and safety of triamcinolone acetonide nasal spray at a dose of 110 micro g in each nostril once daily with 10 mg of oral astemizole once daily for the treatment of seasonal allergic rhinitis. METHODS: A multicenter, double-blind, parallel-group study was conducted in 239 patients who were randomized to receive either triamcinolone acetonide or astemizole. A 5-day, drug-free, lead-in period was followed by 4 weeks of double-blind treatment. One hundred four patients treated with triamcinolone acetonide and 105 patients treated with astemizole could be evaluated. RESULTS: Overall, triamcinolone acetonide was more effective than astemizole in reducing total nasal symptoms, nasal stuffiness, nasal itching, and sneezing (p </= 0.01). Triamcinolone acetonide was superior to astemizole at weeks 1, 2, and 3 in reduction of the total nasal symptom score (p </= 0.0401) and in reduction of nasal stuffiness (p </= 0.05). Improvements in individual nasal symptoms (itching, postnasal drip, runny nose, and sneezing) were greater for triamcinolone acetonide at week 2 (p </= 0.01). Ocular symptoms improved from baseline in both groups. When pollen counts were correlated to mean nasal rhinitis scores, the triamcinolone acetonide group showed continued improvement from week 1 to week 2 in nasal symptoms when pollen counts were at their highest. During the same period, patients treated with astemizole failed to show improvement from week 1 to week 2. This study demonstrated that once daily administration of triamcinolone acetonide was more effective than astemizole for controlling nasal symptoms of seasonal allergic rhinitis, especially during the peak pollination period.

Administration, Intranasal↗
PubMed1996

Comparison of efficacy, safety, and skin test inhibition of cetirizine and astemizole.

BACKGROUND: Astemizole, an H1-histamine-receptor antagonist prescribed for seasonal allergic rhinitis, has a slow onset of action and a strong suppressive effect on the wheal and flare reaction, which interferes with skin testing results. The newer antihistamine cetirizine appears to have a rapid onset of action and a low potential to interfere with posttreatment skin testing results. OBJECTIVE: To compare the efficacy, safety, and skin test inhibition of astemizole and cetirizine in the treatment of seasonal allergic rhinitis. METHODS: In a double-blind, parallel-group study conducted at six sites during ragweed pollination season, 263 subjects were randomized to receive 10 mg of astemizole, 5 mg of cetirizine, or 10 mg of cetirizine daily for 2 weeks. The subjects rated seven allergic rhinitis symptoms daily, the subjects and investigators provided global assessments of the responses to the treatments, and the subjects rated their satisfaction with the treatments. Thirty-nine subjects at one study site underwent quantitative skin testing before and after treatment. RESULTS: As measured by reduction from baseline in total symptom severity score, which was the primary efficacy measure in the study, all three treatments significantly relieved the symptoms of allergic rhinitis (P less than .05). This finding was supported by the global ratings and the subject satisfaction ratings. There were no significant differences among the three treatments for reduction from baseline in total symptom severity score. The mean subject satisfaction score with 10 mg of cetirizine was significantly greater than that with astemizole (P less than .05). In the skin tests performed 3, 7, and 14 days after the end of antihistamine treatment, the subjects who had received the cetirizine doses had significantly greater mean sum of wheal and mean sum of erythema values than those who had received the astemizole dose (P less than .05). Sensitivity to ragweed pollen extract returned to 90% of baseline within three days of the end of cetirizine treatment. Both drugs were well tolerated and their adverse event profiles were similar. CONCLUSIONS: Astemizole and cetirizine are effective and well tolerated in alleviating the symptoms of ragweed-induced allergic rhinitis. Cetirizine inhibits skin test results to a much lesser extent than does astemizole. Physicians may wish to consider the potential for skin test inhibition when selecting an antihistamine for patients with allergic rhinitis.

Adolescent↗
PubMed1997

Onset of action and efficacy of terfenadine, astemizole, cetirizine, and loratadine for the relief of symptoms of allergic rhinitis.

BACKGROUND: Terfenadine, astemizole, cetirizine, and loratadine are compared in their abilities to produce relief of symptoms of allergic rhinitis. OBJECTIVE: The aim of this study was to compare the onset of action and efficacy of the study medications. METHODS: 111 ragweed-sensitive subjects were primed with pollen in the Environmental Exposure Unit. Study entry required adequate symptoms over a 3 hour exposure to 5000 +/- 300 grains/m3 of ragweed pollen. On the test day, subjects were given a single dose of either terfenadine 60 mg (22), astemizole 10 mg (22), cetirizine 10 mg (23), loratadine 10 mg (22), or placebo (22) when sufficiently symptomatic after a 60-minute exposure. Allergen levels were maintained and symptoms recorded every 30 minutes. RESULTS: Proportions of subjects with clinically important relief were cetirizine, 69.6%; terfenadine, 54.5%; loratadine, 50.0%; astemizole, 40.9%; and placebo, 31.8% but differences weren't significant between treatment groups (P = .119). Survival curves for times to onset of clinically important relief for the four treatment groups were not different (P = .119). Subjects realizing definitive relief were cetirizine, 65.2%; terfenadine, 45.5%; loratadine, 31.8%; placebo, 27.3%; and astemizole, 22.7% (P = .023). Survival analysis of onset time for definitive relief found significant differences (P = .010). The ranking was cetirizine --> terfenadine --> loratadine --> astemizole (quickest to slowest). Global evaluation based on subject willingness to take the medication again yielded percentages: cetirizine, 82.6%; terfenadine, 66.7%; astemizole, 63.6%; loratadine, 40.9%; and placebo, 36.4% (P = .036). CONCLUSION: Cetirizine and terfenadine continuously ranked higher in terms of onset of action and efficacy, while loratadine and astemizole ranked lower. Significance was detected in definitive relief and relative efficacy.

Adolescent↗
PubMed1995

Electrophysiological and arrhythmogenic effects of the histamine type 1-receptor antagonist astemizole on rabbit Purkinje fibers: clinical relevance.

Astemizole is a potent histamine H1-antagonist that has been associated with cases of life-threatening cardiac arrhythmias, including torsade de pointes and atrioventricular (AV) block. However, its effects on cardiac action potential (AP) has not been described. We examined the electrophysiological effects of astemizole on rabbit Purkinje fibers using conventional glass microelectrodes in parallel with the effects of the widely used histamine H2-antagonist cimetidine, selected because it has no known cardiac arrhythmic toxicity. Astemizole (0.01-3 microM) exerted a concentration-dependent prolonging effect on final repolarization that did not reach steady state after 3 h of exposure. This effect was more pronounced at low stimulation frequency and was less marked at high stimulation frequency. In addition, early afterdepolarizations (EADs) occurred in one third of the fibers. Increasing extracellular concentration of KCl (2.7-5.4 mM) or MgCl2 (1-5 mM) suppressed EADs and reversed the prolonging effect that was conversely exaggerated by decreasing KCl (4-2.7 mM) or MgCl2 (1-0.5 mM) concentration. At higher concentrations (3-30 microM), astemizole induced an increasing depressant effect on the maximal rate of depolarization (Vmax) that became more pronounced with high stimulation frequency. All parameters were strongly depressed at 10 microM astemizole, leading to cellular inexcitability in 5 of 12 fibers when exposed to 30 microM astemizole. In comparison, cimetidine induced minor changes on AP characteristics, i.e., a prolongation in plateau duration at high (30-100 microM) concentrations. These results provide evidence that astemizole exerts quinidine-like effects on cardiac APs that are compatible with the occurrence of the clinically observed arrhythmias.

Action Potentials↗
PubMed1990

Antiallergic effects of astemizole on immediate type hypersensitivity reactions.

Astemizole (0.5-5 mg/kg, p.o.) dose-dependently inhibited heterologous and homologous PCA reactions in rats at ID50 values of 1.48 mg/kg and 2.37 mg/kg, respectively. The inhibitory effect of astemizole on heterologous PCA was most remarkable when this compound was given p.o. 2 h prior to antigen challenge. Astemizole (0.1-5 mg/kg, p.o.) dose-dependently inhibited experimentally-induced asthma in guinea pigs at an ID50 of 0.86 mg/kg. Ex vivo, astemizole (0.5-5 mg/kg, p.o.) inhibited antigen-induced histamine release from lung pieces of sensitized guinea pigs. In in vitro experiments, the drug dose-dependently inhibited antigen-induced histamine and SRS-A releases from guinea pig lung pieces at concentrations of 0.05-10 microM. Furthermore, astemizole (0.1-10 microM) inhibited the histamine release induced by compound 48/80 and antigen-antibody reaction from rat peritoneal mast cells, and at 0.1-500 nM inhibited both leukotriene C4- and platelet-activating factor (PAF)-induced contraction of isolated guinea pig trachea at submicromolar concentrations. Astemizole not only inhibited 45Ca uptake into rat mast cells but also prevented the Ca2+ release from the intracellular Ca store induced by compound 48/80, although this compound did not affect the histamine release from permeabilized mast cells induced by Ca2+. Our results suggest that one of the antiallergic mechanisms of astemizole may be an inhibition of signal transduction from the mast cell membrane to the intracellular systems.

Airway Resistance↗
PubMed1985

Astemizole--a new, non-sedating antihistamine for hayfever.

Astemizole, a new histamine H1 receptor blocker, was compared with placebo in an eight week, double-blind trial in the treatment of seasonal allergic rhinitis. Sixty-five patients of either sex were randomized to either astemizole (32 patients: 10 mg t.i.d. on day 1, 10 mg b.i.d. on day 2, 10 mg o.d. for the remainder of the study) or placebo (33 patients). Patients were seen bi-weekly and maintained a daily diary record of symptoms throughout the study. Significantly more patients in the placebo group (12) compared to the astemizole group (2) dropped out of the study due to treatment failure (p less than 0.05). Astemizole significantly reduced the frequency and severity of allergic symptoms. In subjective evaluations of each treatment by both the investigator and the patients, astemizole was judged good to excellent by 68% compared to 30% for placebo (p less than 0.05). One patient in each group experienced drowsiness. The only significant side effect of astemizole was weight gain (20 patients compared to 1 in the placebo group), although only one patient discontinued astemizole for this reason.

Adolescent↗
PubMed1988

[General review of a non-sedative antihistaminic, astemizole (Hismanal), a H1 receptor antagonist].

The non-sedating antihistamine Astemizole seems to approach all the major characteristics of the ideal histamine H1 antagonist, according to a comprehensive review of 54 clinical trials and clinical use in over 6,500,000 patients worldwide. The following statements concerning Astemizole can now be made: Astemizole is more potent than any other known antihistamine, following Astemizole therapy, H1 blockade is complete in the main target tissues, such as nasal and ocular mucosa, this blockade is also specific, since all histamine-mediated signs and symptoms respond to the drug, this blockade is maintained, since tolerance does not appear during long-term treatment. Astemizole is a non-sedative and non-toxic drug, even during chronic use. Astemizole is very effective in patients with chronic urticaria. Astemizole has well-documented beneficial protective effects on histamine-induced bronchoconstriction.

Astemizole↗
PubMed1985

Astemizole and other H1-antihistaminic drug treatment of asthma.

The disparity between the activation of mast cells in the airways of patients with allergic asthma and the lack of efficacy of H1-antihistamines in asthma therapy has been difficult to reconcile. Histamine causes bronchoconstriction when inhaled by subjects with asthma and is released in detectable amounts into the circulation after bronchial provocation with an antigen. However, it is only weakly antagonized at bronchial H1-receptors by conventional antihistamines such as chlorpheniramine and clemastine, achieving dose ratios of 2 to 4 at maximally tolerated doses. Astemizole and terfenadine are two new H1-histamine antagonists with greatly increased potency and no sedative and anticholinergic side effects. Astemizole has a delayed onset of maximal activity but induces prolonged H1-blockade that extends 15 to 30 days after the end of treatment, whereas terfenadine has a rapid onset of action with a much shorter duration of effect. With therapeutic doses (10 mg/day), astemizole is at least four times more potent in antagonizing histamine-induced bronchoconstriction than the previously available H1-antihistamines and also effectively antagonizes antigen-induced bronchoconstriction in asthma. Astemizole has been shown to be highly effective in the symptomatic treatment of seasonal allergic rhinoconjunctivitis, with the exception of nasal obstruction. With continued treatment, astemizole also offers useful protection from the symptoms of seasonal asthma. Thus the role of histamine in the pathogenesis of asthma should be reappraised. Potent H1-histamine antagonists such as astemizole and terfenadine may offer some benefit in asthma therapy, but the precise clinical indications for their use will require critical evaluation.

Astemizole↗
PubMed1989

Comparison of beclomethasone dipropionate aqueous nasal spray, astemizole, and the combination in the prophylactic treatment of ragweed pollen-induced rhinoconjunctivitis.

The clinical efficacy and side effect of (1) beclomethasone dipropionate aqueous nasal spray, 400 micrograms daily, (2) astemizole, 10 mg daily, and (3) beclomethasone, 400 micrograms, plus astemizole, 10 mg daily, were compared in a double-blind, randomized, parallel-group trial. Ninety adults were matched into groups of three according to sensitivity to ragweed pollen. One of each of the three subjects was assigned to nasal spray alone, one was assigned to astemizole alone, and one subject was assigned to both medications. Medications were started 1 week before and continued daily until 1 week after the ragweed-pollen season (6 weeks). If rhinoconjunctivitis was inadequately controlled with the trial medications, pressurized steroid nasal spray and/or antihistamine-decongestant eye drops were used in the minimum dose that would ensure relief. Nose and eye symptoms and concomitant medication use were recorded daily in a diary. Sneezing, nasal obstruction, and rhinorrhea were significantly better, and less additional nasal spray was used in subjects taking beclomethasone alone than in subjects taking astemizole alone. Beclomethasone plus astemizole provided no better control of rhinitis than beclomethasone alone. Eye symptoms and eye drop use tended to be less in subjects taking astemizole alone than in subjects taking beclomethasone alone, but the best control of eye symptoms was recorded in the subjects taking both trial medications. Side effects were mild or transient.

Administration, Intranasal↗
PubMed1995

Cetirizine and astemizole therapy for chronic idiopathic urticaria: a double-blind, placebo-controlled, comparative trial.

BACKGROUND: Cetirizine and astemizole have been shown to be safe and effective in the treatment of patients with chronic idiopathic urticaria. Cetirizine brings about clinical benefit more rapidly. OBJECTIVE: The purpose of this study was to compare the efficacy of single daily doses of cetirizine and astemizole in relieving the symptoms of chronic idiopathic urticaria, with particular emphasis on the commencement of action. METHODS: Patients with chronic idiopathic urticaria were randomly assigned to relieve either 10 mg of cetirizine, 10 mg of astemizole, or placebo for 4 weeks in a multicenter double-blind trial. Patients rated symptom severity each night, and investigators rated symptoms weekly. RESULTS: One hundred eighty-seven patients were enrolled in the trial; 180 were included in the safety analysis and 177 were included in at least one efficacy analysis. Both cetirizine and astemizole were significantly superior to placebo in relieving symptoms of chronic idiopathic urticaria. Both patients' and investigators' ratings indicated that cetirizine acted more rapidly. Both active treatments were well tolerated, and the incidence of somnolence did not differ statistically between cetirizine (14.5%) and astemizole (10.3%). CONCLUSION: Both cetirizine and astemizole provide effective relief of the symptoms of chronic idiopathic urticaria with similar side-effect profiles. However, clinical benefit occurs significantly more rapidly with cetirizine.

Adult↗
PubMed1991

Detection and determination of free and plasma protein-bound astemizole by thin-layer chromatography: a useful technique for bioavailability studies.

A thin-layer chromatographic (TLC) procedure has been developed for the determination of astemizole in plasma as the free and as protein-bound substance. The detection and quantification were performed without using internal standards. In earlier described methods for the estimation of astemizole by high-performance liquid chromatography and radioimmunoassay, only free levels in plasma were quantified, at 3.3% of the total astemizole, with the remaining 96.7% bound to plasma protein and tissue. Our method employs proteolysis of plasma proteins by incubating plasma for 2 h in pepsin. After proteolysis the astemizole is extracted, and a known amount of the extract is spotted on precoated silica gel F 254 plates. Astemizole was quantified using a Shimadzu CS-930 dual-wavelength TLC scanner. The method provides a direct estimate of total astemizole present in the plasma.

Animals↗
PubMed1986

Comparison of the suppressive effect of astemizole, terfenadine, and hydroxyzine on histamine-induced wheals and flares in humans.

Thirty-two healthy volunteers completed a 14-day, double-blind, noncrossover study comparing the efficacy and adverse effects of astemizole, terfenadine, and hydroxyzine. The subjects received either astemizole (load), 30 mg once daily for 1 week and then 10 mg once daily for 1 week, or astemizole (no load), 10 mg once daily for 2 weeks, or terfenadine, 60 mg twice daily for 2 weeks, or hydroxyzine, 50 mg once daily for 2 weeks. Before and on days 7 and 14 of treatment, five intradermal tests with various amounts of histamine phosphate (range 0.3 to 40 micrograms) were performed. Wheal-and-flare responses were traced, and the areas were computed by use of a graphics tablet. All four H1-receptor antagonist treatment regimens were equally effective in reducing the flare response to histamine. Astemizole (load) and hydroxyzine were significantly more effective than terfenadine and astemizole (no load) in reducing wheal size. The incidence of adverse effects, including sedation, was low overall and lowest in the astemizole (no load) and terfenadine groups, although this difference was not statistically significant.

Adult↗
PubMed1998

Evaluation of the potential cardiotoxicity of the antihistamines terfenadine, astemizole, loratadine, and cetirizine in atopic children.

BACKGROUND: Adverse cardiac effects have been related to the use of H1-receptor antagonists terfenadine and astemizole. OBJECTIVE: We have investigated the cardiac effects of the H1-receptor antagonists terfenadine, astemizole, loratadine and cetirizine, used in recommended doses, concomitantly or not with the antibiotic erythromycin. METHODS: A group of 80 children aged 5 to 12 years was studied. All children had been diagnosed with perennial allergic rhinitis based on symptoms, clinical signs and a positive immediate skin test to Dermatophagoides pteronyssinus. The children had no personal history of cardiac disease or hepatic dysfunction, and they had a normal electrocardiogram (ECG) at the beginning of the study. Forty children had allergic rhinitis and sinusitis, and were assigned to subgroups of ten children who received terfenadine, astemizole, loratadine, or cetirizine, concomitantly with erythromycin, for 14 days. Erythromycin was started to treat presumed bacterial infection in children with complete radiologic opacification of the maxillary sinus(es). The remaining 40 children had no sinusitis, and were assigned to subgroups of 10 children who received terfenadine, astemizole, loratadine, or cetirizine for 14 days. RESULTS: No significant changes in the QT interval and QTc (QT corrected by Bazzett's equation) were observed among children who received astemizole, loratadine or cetirizine, with or without erythromycin. Children who have received terfenadine and erythromycin showed significantly prolonged QT interval (mean pretreatment and posttreatment values 0.32s and 0.34s, respectively). Analysis of the QTc interval, however, showed no significant differences in the group treated with terfenadine and erythromycin (mean values 0.39s and 0.39s, respectively). CONCLUSIONS: Our results show that H1-receptor antagonists terfenadine, astemizole, loratadine and cetirizine, administered with or without erythromycin, to atopic children in recommended doses, do not induce adverse cardiac effects. Although the association between terfenadine and erythromycin has caused a statistically significant increase in QT interval measurements, the magnitude of these changes was below levels considered cardiotoxic or clinically relevant.

Anti-Allergic Agents↗
PubMed1985

A comparison of astemizole and chlorpheniramine in dermographic urticaria.

The effects of the H I receptor antagonists astemizole and chlorpheniramine on dermographism were compared in a double-blind study in sixteen patients. Both drugs resulted in a parallel and significant depression of the dermographic force-response curve and an elevation of the weal-force threshold, but the changes were greater in the patients receiving astemizole (a maximal potency shift of 74% for astemizole and 37% for chlorpheniramine). Subjective itch (10 cm line) and frequency of dermographic episodes were also reduced more by astemizole than by chlorpheniramine. The effect of astemizole was greater at 4 weeks than at 2 weeks, whereas the effect of chlorpheniramine had decreased at 4 weeks. The effect of astemizole but not chlorpheniramine was still apparent 4 weeks after treatment had been stopped. Since the degree of residual dermographism was comparable despite great differences in histamine weal inhibition a vasoactive mechanism in addition to that mediated by histamine must be involved in dermographic urticaria.

Adolescent↗
PubMed1995

Cardiac electrophysiological actions of the histamine H1-receptor antagonists astemizole and terfenadine compared with chlorpheniramine and pyrilamine.

We compared the cardiac electrophysiological actions of two types of H1-receptor antagonists--the piperidines, astemizole and terfenadine, and the nonpiperidines, chlorpheniramine and pyrilamine-in vitro in guinea pig ventricular myocytes and in vivo in chloralose-anesthetized dogs. Astemizole and terfenadine significantly increased action potential duration of guinea pig myocytes. This concentration-dependent prolongation of action potential duration was reverse frequency dependent and led to development of early afterdepolarizations, which occurred more frequently at higher concentrations and slower pacing frequencies. Astemizole and terfenadine potently blocked the rapidly activating component of the delayed rectifier, IKr, with IC50 values of 1.5 and 50 nmol/L, respectively. At 10 mumol/L, terfenadine but not astemizole blocked the slowly activating component of the delayed rectifier, IKs (58.4 +/- 3.1%), and the inward rectifier, IK1 (20.5 +/- 3.4%). Chlorpheniramine and pyrilamine blocked IKr relatively weakly (IC50 = 1.6 and 1.1 mumol/L, respectively) and IKs and IK1 less than 20% at 10 mumol/L. Astemizole and terfenadine (1.0 to 3.0 mg/kg IV) significantly prolonged the QTc interval and ventricular effective refractory period in vivo. Chlorpheniramine and pyrilamine (< or = 3.0 mg/kg) did not significantly affect these parameters. Block of repolarizing K+ currents, particularly IK1, by astemizole and terfenadine produces reverse rate-dependent prolongation of action potential duration and development of early afterdepolarizations, delays ventricular repolarization, and may underlie the development of torsade de pointes ventricular arrhythmias observed with the use and abuse of these agents.

Action Potentials↗
PubMedDate not supplied

A parallel-group comparison of astemizole and loratadine for the treatment of perennial allergic rhinitis.

The efficacy and safety of the two antihistamines, astemizole and loratadine, were compared in a double-blind study of 84 patients with perennial allergic rhinitis. Patients were randomized to receive orally either astemizole 10 mg once daily (n = 40) or loratadine 10 mg once daily (n = 44) for 1 week. No other antirhinitis medication was allowed during the study. By day 7 the mean daily symptom scores, recorded on diary cards, were lower in patients receiving astemizole than in those receiving loratadine for runny nose, itchy nose and sneezing, although not for blocked nose, and treatment differences only reached statistical significance for runny nose. After 7 days, 53.75% of patients on astemizole and 38.6% on loratadine were free of symptoms, and 87% of patients on astemizole described the treatment as good or excellent compared with 62% on loratadine. The present results suggest that astemizole may be more effective than loratadine in controlling symptoms of perennial allergic rhinitis.

Administration, Oral↗
PubMed1997

Effects of astemizole on ventricular activation delay and RT intervals in a canine myocardial infarction model.

In order to clarify the arrhythmogenic effects of nonsedating antihistamines, we examined the effects of astemizole, a nonsedating antihistamine, on ventricular activation and RT intervals in a canine myocardial infarction model. Myocardial infarction was produced by two-stage ligation of the left anterior descending coronary artery in dogs. Seven days after ligation, bipolar electrodes were sutured on the ventricular surface of the infarcted and normal zones to apply an electrical stimulation or record the ventricular activation. An electrical stimulation with coupling intervals between 300 and 140 ms was applied on the ventricular surface of the normal zone during atrial pacing, and the ventricular activation delay was measured. The effect of astemizole on the RT interval was also determined during atrial pacing, sinus rhythm or after premature stimulation. The ventricular activation delay increased after astemizole at doses of 0.3 to 3 mg/kg in the infarcted and at 3 mg/kg in the normal zones, and the effect of astemizole was greater in the infarcted zone. Astemizole increased the RT interval in the normal zone to a greater extent at a long coupling interval. The increase in the RT interval was greater in the infarcted zone compared with that in the normal zone. In conclusion, astemizole increased the activation delay in the infarcted zone, probably through prolongation of the repolarization time, and its effect on the activation delay may be arrhythmogenic.

Animals↗
PubMed1991

Antiallergic effects of major metabolites of astemizole in rats and guinea pigs.

Antiallergic effects of astemizole (CAS 68844-77-9) and its metabolites were studied using rats and guinea pigs. All the metabolites of astemizole tested i.e., desmethylastemizole, 6-hydroxydesmethylastemizole and norastemizole, were more active than astemizole in inhibiting the contraction of the ileum as well as the bronchoconstriction induced by histamine in guinea pigs. Desmethylastemizole was about the same as the parent compound in inhibiting the 3H-mepyramine binding in guinea pig cerebellum. In heterologous passive cutaneous anaphylaxis (PCA) and homologous PCA, the metabolites caused almost equipotent inhibition to that seen in astemizole. On the other hand, in the studies of histamine release from rat peritoneal mast cells induced by compound 48/80 or from lung fragments in actively sensitized guinea pigs, desmethylastemizole, 6-hydroxydesmethylastemizole and norastemizole were much less potent than was astemizole. No H2-antagonistic activity was observed with either astemizole or desmethylastemizole.

Animals↗