Plasma concentrations of praziquantel during the therapy of neurocysticerosis with praziquantel, in the presence of antiepileptics and dexamethasone.

Plasma praziquantel concentrations were measured in 11 Thai patients with active neurocysticercosis (8 males and 3 females). Praziquantel (Biltricide 600 mg per tablet) was given at a daily dose of 45 mg/kg given in 3 divided doses for 15 consecutive days. All patients had significant improvement with resolution of symptoms and signs, and reduction of active lesions of cysticercosis shown by the brain computed tomographic scanning. After oral administration, the drug was rapidly absorbed from the gastrointestinal tract. There was substantial inter-individual variability in plasma concentrations of praziquantel. After the first dose, maximum plasma concentrations in the range of 42-540 ng/ml was attained at 30 minutes to 5 hours. In all cases, the drug almost totally disappeared from plasma within 8 hours; drug levels measured prior to the first doses on the following days showed undetectable levels. The area under the plasma concentration-time curves of praziquantel following the first dose were between 125 and 990 ng hour/ml. The results suggested that the unusual low plasma availability of the drug observed in this group of patients could be a consequence of pharmacokinetic drug interactions of the concomitant therapy with antiepileptic drugs and dexamethasone. Active metabolite(s), rather than praziquantel itself, may play a significant part in the therapy of neurocysticerosis.