Pharmacokinetics of astemizole in children.

Astemizole is often administered to children in the treatment of rhinoconjunctivitis and urticaria with good efficacy and few side effects. Both astemizole and its major metabolite desmethylastemizole (DMA) are clinically effective without annoying side effects such as sedation. The pharmacokinetics in adults is well known. In three different studies we have investigated the pharmacokinetical properties of the drug in children. Study I (absorption): Thirty-eight children 8-16 years old (mean 12.6 years) and weighing 25-80 kg (mean 45 kg), with rhinoconjunctivitis due to birch pollinosis, were pretreated with either astemizole 5 mg daily or placebo for two weeks. Then, all children were treated with astemizole in doses increasing every week, i.e. 5, 10, 20 and 40 mg per day. There was a good correlation between the given dose per kg body weight and the plasma concentration of astemizole plus hydroxylated metabolites, indicating that astemizole is completely absorbed. Study II (time to reach steady state): A group of 21 children 7-18 years old (mean 13.9 years), plus 2 younger children, 2 and 5 years old, with allergy against birch- or grass pollen were treated with astemizole 10 mg daily for 12 weeks. Astemizole had reached steady-state plasma levels when the first sample was taken after 1 week, DMA reached steady state within 4 weeks. Study III (elimination half-life [t1/2 beta]): In 10 of the children from study II, t1/2 beta for astemizole plus DMA could be calculated (two samples) and was 10.8 days.(ABSTRACT TRUNCATED AT 250 WORDS)