The bioavailability of carbamazepine.

Two aspects of the correlation of plasma carbamazepine level with drug dose in patients taking carbamazepine tablets indicated the possibility that the drug may be incompletely and variably absorbed from the alimentary tract of man. To investigate this possibility, pharmacokinetic studies were undertaken in six volunteers, who were given increasing single doses of carbamazepine in tablet form at appropriate intervals. These studies gave evidence of slow, and probably incomplete, absorption of carbamazepine. After administration of carbamazepine in a specially-prepared solution to 5 of the subjects, rapid absorption of the drug occurred, and in 4 subjects more drug was absorbed than when the same normal dose was given as tablets. It was concluded that the pharmaceutical formulation of carbamazepine tablets limits the bioavailability of the drug, and that problems may arise if the bioavailability of the drug is to be increased.