Pharmacokinetics of carbamazepine derived from a new tablet formulation

The pharmacokinetics of a new tablet formulation of carbamazepine, an antiepileptic agent, have been investigated in 9 normal healthy subjects. The drug was given as a single oral dose of 400 mg. Ten blood samples were collected after administration. Plasma carbamazepine concentrations were determined by a sensitive method (HPLC). Areas under the plasma level-time curves for each subject were evaluated by means of the trapezoidal rule. The peak plasma concentration of 3.96-8.25 mg/l was reached 4-24 h after drug administration. The terminal phase half-life was 22.19-39.61 h and a systemic clearance was 1.05-2.06 l/h. The new tablet formulation of carbamazepine seems to be bioequivalent when compared to the one used so far. For the prediction of systemic availability and estimation of the first-pass metabolism, from plasma level data, a hepatic blood flow rate limited model were used. The systemic availability was 97.8-98.9% and the elimination of the drug on its first-pass through the liver was 1.13-2.20%.