Abstract
A high-performance liquid chromatographic method was developed for the measurement of carbamazepine (CBZ) and carbamazepine 10,11-epoxide (CBZE) in human breast milk and plasma. The method involves rapid C18 solid-phase extraction of CBZ and CBZE. Chromatographic separation was achieved with a reversed-phase C8 column using a mobile phase of potassium dihydrogenphosphate (pH 2·5) and acetonitrile (67:33 v/v), with ultraviolet detection at 254 nm. 2-Methyl CBZ was used as the internal standard. Determination of both CBZ and CBZE was possible in the range of 0·01 - 6·0 mg/L and 0·02 - 6·0 mg/L in milk and plasma, respectively. The recoveries of CBZ and CBZE added to the milk and plasma were 90·6 - 98.0% and 88·9 - 104·0%, respectively, with coefficients of variation less than 8·3% and 10·5%, respectively. The method has been used for drug level monitoring in milk and plasma samples obtained from CBZ-treated patients. The mean (SD) levels for CBZ in milk and plasma samples were 3·50 (0·4) mg/L and 6·18 (2·9) mg/L, and for CBZE were 1·28 (0·3) mg/L and 1·85 (1·0) mg/L, respectively. The mean (SD) milk/plasma ratios of CBZ and CBZE were 0·64 (0·2) and 0·79 (0·3), respectively. The milk/plasma ratio of CBZE was slightly higher than that of CBZ.