Etibendazole

A sensitive and specific radioimmunoassay procedure was developed for mebendazole and flubendazole enabling a more thorough study of the systemic absorption and pharmacokinetic behaviour of the drugs. In rats, plasma levels of oral and subcutaneous mebendazole were about 10 times higher than those of flubendazole. The pro-drug R 34 803 showed levels of metabolically formed flubendazole similar to those found for mebendazole. Intramuscular flubendazole in dogs, injected for 5 consecutive days, produced sustained fairly high plasma levels for at least 6 weeks after the last dose. The absorption of oral flubendazole in man was markedly enhanced when the drug was taken together with a meal. A 20-times higher dose, however, produced only an increase by 1.4 of the plasma levels and AUC-values, indicating that the absorption of flubendazole is limited by the extremely poor solubility of the drug in the contents of the gastrointestinal tract.