Bioavailability of phenobarbital by rectal administration.

Phenobarbital was administered to five patients, eight to 20 years of age, by four different administration routes: Intravenous, intramuscular, oral, and rectal. At each administration, extent of bioavailability, elimination rate constant, absorption rate constant, and volume of distribution of phenobarbital were calculated using a one-compartment open model. The results obtained suggest that rectal administration of phenobarbital is more reliable than intramuscular or oral administration of the drug for rapid treatment in children.