Allongement du temps QT
Événements indésirables médicamenteux
|Réactions cutanées allergiques|
Variantes ✨Pour une évaluation intensive des variantes par ordinateur, veuillez choisir l'abonnement standard payant.
Explications concernant les substances pour les patients
Nous n'avons pas de mise en garde supplémentaire concernant l'association de cyaméazine et de astémizole. Veuillez également consulter les informations pertinentes des spécialistes.
Les changements d'exposition rapportés correspondent aux changements de la courbe concentration-temps plasmatique [ AUC ]. Nous ne prévoyons aucun changement dans l'exposition à la cyaméazine, lorsqu'il est associé à la astémizole (100%). Nous ne prévoyons aucun changement dans l'exposition à la astémizole, lorsqu'il est associé à la cyaméazine (100%).
Les paramètres pharmacocinétiques de la population moyenne sont utilisés comme point de départ pour calculer les changements individuels d'exposition dus aux interactions.
La biodisponibilité de la cyaméazine est inconnue. La liaison aux protéines [ Pb ] n'est pas connue. Le métabolisme ne se fait pas via les cytochromes communs.
La astémizole a une faible biodisponibilité orale [ F ] de 3%, c'est pourquoi la concentration plasmatique maximale [Cmax] a tendance à changer fortement avec une interaction. La demi-vie terminale [ t12 ] est de 22 heures et des taux plasmatiques constants [ Css ] sont atteints après environ 88 heures. La liaison aux protéines [ Pb ] est 97% forte. Le métabolisme a lieu via CYP2D6 et CYP3A4, entre autres.
|Effets sérotoninergiques a||0||Ø||Ø|
Note: À notre connaissance, ni la cyaméazine ni la astémizole n'augmentent l'activité sérotoninergique.
|Kiesel & Durán b||3||+++||Ø|
Recommandation: Par mesure de précaution, une attention particulière doit être portée aux symptômes anticholinergiques, en particulier après augmentation de la dose et à de celles situées dans la marge thérapeutique supérieure.
Notation: La cyaméazine augmente considérablement l'activité anticholinergique. À notre connaissance, la astémizole n'augmente pas l'activité anticholinergique.
Allongement du temps QT
Note: En association, la cyaméazine et la astémizole peuvent potentiellement déclencher des arythmies ventriculaires de type torsades de pointes.
Effets indésirables généraux
|Effets secondaires||∑ fréquence||cya||ast|
|Réactions cutanées allergiques||1.0 %||+||n.a.|
|Syndrome malin des neuroleptiques||0.0 %||0.01||n.a.|
Sur la base de vos réponses et des informations scientifiques, nous évaluons le risque individuel d'effets secondaires indésirables. Ces recommandations sont destinées à conseiller les professionnels et ne se substituent pas à la consultation d'un médecin. Dans la version d'essai (alpha), le risque de toutes les substances n'a pas encore été évalué de manière concluante.
Abstract: Astemizole is a long-acting, highly selective histamine1-receptor antagonist with minimal central and anticholinergic effects. Comparison studies have shown astemizole to be equal or superior to currently available antihistamines, beclomethasone nasal spray, and cromolyn sodium in relieving allergic symptoms of seasonal and perennial allergic rhinitis. Other uses include treatment of allergic conjunctivitis and chronic urticaria. Astemizole is not as effective for treatment of acute allergic symptoms because of its delayed onset of action. Astemizole and its active metabolite, desmethylastemizole, have long elimination half-lives permitting once-daily dosing. The incidence of sedation is lower than with conventional antihistamines, but increased appetite and weight gain do occur. Astemizole should be useful for both maintenance and prophylactic therapy in patients with chronic allergic conditions who cannot tolerate the sedative or anticholinergic effects of conventional antihistamines.
Abstract: Astemizole is an H1-histamine receptor antagonist with a long duration of action permitting once daily administration. Its efficacy in seasonal and perennial allergic rhinitis has been convincingly demonstrated, and several comparative studies suggest that astemizole is at least as effective as some other H1-histamine receptor antagonists. A few smaller studies have shown beneficial effects on the symptoms of allergic conjunctivitis and chronic urticaria (but not atopic dermatitis). While astemizole appears to share with other H1-histamine receptor antagonists a tendency to increase appetite and cause weight gain after prolonged use, it offers the important advantage of an absence of significant central nervous system depression or anticholinergic effects with usual doses. Thus, astemizole offers a worthwhile improvement in side effect profile over 'traditional' H1-histamine receptor antagonists, especially in patients bothered by the sedative effects of these drugs.
Abstract: An overdose of astemizole predisposes the myocardium to ventricular dysrhythmias, including torsades de pointes. Herein we describe a case of astemizole-induced torsades de pointes ventricular tachycardia and also review previous case reports in the literature. All the patients were young, and dysrhythmias developed only in those with corrected QT intervals greater than 500 ms. Although several mechanisms have been postulated, no clear explanation has been provided for why astemizole promotes myocardial dysrhythmias. Treatment of astemizole-induced torsades de pointes includes discontinuing use of astemizole, intravenous administration of magnesium sulfate and isoproterenol, temporary cardiac pacing, and, when necessary, direct current cardioversion. A cardiac cause of syncope or convulsions must not be overlooked, especially in patients taking H1 antagonists because they often have these symptoms before hospitalization or detection of torsades de pointes (or both).
Abstract: No Abstract available
Abstract: A 26 year-old woman was admitted to the hospital two hours after astemizole overdose. Electrocardiograph showed a prolonged QT interval. Torsade de pointes occurred 13 h after ingestion. Plasma levels of astemizole plus hydroxylated metabolites showed an apparent plasma half-life of 17 h. The possible occurrence of torsade de pointes in astemizole overdose, and the long elimination time of astemizole and hydroxylated metabolites, makes it necessary to maintain ECG monitoring until QT interval has returned to normal.
Abstract: AIMS: The aim of this study was to investigate the influence of chronic itraconazole treatment on the pharmacokinetics and cardiovascular effects of single dose astemizole in healthy subjects was studied. METHODS: Twelve male volunteers were taking orally 200 mg twice daily itraconazole or placebo for 14 days with a washout period of 4 weeks in between. Approximately 2 h after the morning dose of itraconazole or placebo on day 11, 10 mg astemizole was orally administered. The plasma concentrations of astemizole and desmethylastemizole were measured by radioimmunoassay up to 504 h after administration; electrocardiograms with analysis of the QTc interval were recorded up to 24 h post administration. RESULTS: Itraconazole treatment did not significantly change the peak concentration of astemizole (0.74 vs 0.81 ng ml-1) but it increased the area under the curve from 0 to 24 h (5.46 to 9.95 ng ml-1 h) and from 0 to infinity (17.4 to 48.2 ng ml-1 h), and the elimination half-life (2.1 to 3.6 days). The systemic bioavailability of desmethylastemizole was also increased. The QTc interval did not increase after astemizole administration and there was no difference in the QTc intervals between the itraconazole and placebo session. CONCLUSIONS: Chronic administration of itraconazole influences the metabolism of single dose astemizole in normal volunteers without changes of cardiac repolarization during the first 24 h after astemizole administration. However, the reduction in astemizole clearance under concomitant administration of itraconazole may result in a marked increase in astemizole plasma concentrations and QTc alterations during chronic combined intake of astemizole with itraconazole.
Abstract: 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.
Abstract: AIMS: The aims of the present study were to investigate the metabolism of astemizole in human liver microsomes, to assess possible pharmacokinetic drug-interactions with astemizole and to compare its metabolism with terfenadine, a typical H1 receptor antagonist known to be metabolized predominantly by CYP3A4. METHODS: Astemizole or terfenadine were incubated with human liver microsomes or recombinant cytochromes P450 in the absence or presence of chemical inhibitors and antibodies. RESULTS: Troleandomycin, a CYP3A4 inhibitor, markedly reduced the oxidation of terfenadine (26% of controls) in human liver microsomes, but showed only a marginal inhibition on the oxidation of astemizole (81% of controls). Three metabolites of astemizole were detected in a liver microsomal system, i.e. desmethylastemizole (DES-AST), 6-hydroxyastemizole (6OH-AST) and norastemizole (NOR-AST) at the ratio of 7.4 : 2.8 : 1. Experiments with recombinant P450s and antibodies indicate a negligible role for CYP3A4 on the main metabolic route of astemizole, i.e. formation of DES-AST, although CYP3A4 may mediate the relatively minor metabolic routes to 6OH-AST and NOR-AST. Recombinant CYP2D6 catalysed the formation of 6OH-AST and DES-AST. Studies with human liver microsomes, however, suggest a major role for a mono P450 in DES-AST formation. CONCLUSIONS: In contrast to terfenadine, a minor role for CYP3A4 and involvement of multiple P450 isozymes are suggested in the metabolism of astemizole. These differences in P450 isozymes involved in the metabolism of astemizole and terfenadine may associate with distinct pharmacokinetic influences observed with coadministration of drugs metabolized by CYP3A4.
Abstract: BACKGROUND: Antipsychotics (APs) have been associated with risk of torsade de Pointes (TdP). This has important public health implications. Therefore, (a) we exploited the public FDA Adverse Event Reporting System (FAERS) to characterize their torsadogenic profile; (b) we collected drug utilization data from 12 European Countries to assess the population exposure over the 2005-2010 period. METHODS: FAERS data (2004-2010) were analyzed based on the following criteria: (1) ≥ 4 cases of TdP/QT abnormalities; (2) Significant Reporting Odds Ratio, ROR [Lower Limit of the 95% confidence interval>1], for TdP/QT abnormalities, adjusted and stratified (Arizona CERT drugs as effect modifiers); (3) ≥ 4 cases of ventricular arrhythmia/sudden cardiac death (VA/SCD); (4) Significant ROR for VA/SCD; (5) Significant ROR, combined by aggregating TdP/QT abnormalities with VA and SCD. Torsadogenic signals were characterized in terms of signal strength: from Group A (very strong torsadogenic signal: all criteria fulfilled) to group E (unclear/uncertain signal: only 2/5 criteria). Consumption data were retrieved from 12 European Countries and expressed as defined daily doses per 1,000 inhabitants per day (DID). RESULTS: Thirty-five antipsychotics met at least one criterium: 9 agents were classified in Group A (amisulpride, chlorpromazine, clozapine, cyamemazine, haloperidol, olanzapine, quetiapine, risperidone, ziprasidone). In 2010, the overall exposure to antipsychotics varied from 5.94 DID (Estonia) to 13.99 (France, 2009). Considerable increment of Group A agents was found in several Countries (+3.47 in France): the exposure to olanzapine increased across all Countries (+1.84 in France) and peaked 2.96 in Norway; cyamemazine was typically used only in France (2.81 in 2009). Among Group B drugs, levomepromazine peaked 3.78 (Serbia); fluphenazine 1.61 (Slovenia). CONCLUSIONS: This parallel approach through spontaneous reporting and drug utilization analyses highlighted drug- and Country-specific scenarios requiring potential regulatory consideration: levomepromazine (Serbia), fluphenazine (Slovenia), olanzapine (across Europe), cyamemazine (France). This synergy should be encouraged to support future pharmacovigilance activities.