DETERMINATION OF TOTAL AND FREE CARBAMAZEPINE AND THE PRINCIPAL METABOLITES IN SERUM BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH PHOTODIODE-ARRAY DETECTION
H. Liu et al., DETERMINATION OF TOTAL AND FREE CARBAMAZEPINE AND THE PRINCIPAL METABOLITES IN SERUM BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH PHOTODIODE-ARRAY DETECTION, Therapeutic drug monitoring, 15(4), 1993, pp. 317-327
A precise and accurate high-performance liquid chromatography (HPLC) m
ethod has been established for the simultaneous analysis of carbamazep
ine (CBZ), carbamazepine-10,11-epoxide (CBZ-E), and trans-10,11-dihydr
oxy-10,11-dihydro-CBZ (CBZ-H) in serum samples and their ultrafiltrate
s. CBZ and its metabolites are eluted in a 3-muM ODS-Hypersil column (
250 x 2 mm) at a column temperature of 40-degrees-C. The mobile phase
is a mixture containing potassium phosphate buffer-acetonitrile-methan
ol (110:50:30, vol/vol/vol) at a flow rate of 0.2 ml/min. Signals are
monitored by a photodiode-array detector with a main sample wavelength
of 215 nm and a bandwidth of 10 nm. Coefficients of variation (CVs) f
or within- and between-day are within 5%, with the recovery rates rang
ing from 98.16 to 104.64%. This method has the necessary sensitivity a
nd linearity for routine therapeutic monitoring of both total and free
CBZ and its principal metabolites. Total serum concentrations of CBZ,
CBZ-E, and CBZ-H obtained from 55 epileptic children were 12.58 +/- 4
.42, 2.45 +/- 1.22, and 5.83 +/- 3.17 (mean +/- SD, mug/ml), respectiv
ely. Levels of free CBZ, CBZ-E, and CBZ-H were 2.59 +/- 0.93, 1.05 +/-
0.57 and 3.73 +/- 1.87, respectively. Free fractions of CBZ, CBZ-E, a
nd CBZ-H were 20.98 +/- 4.34, 42.63 +/- 8.21, and 65.41 +/- 7.80%, res
pectively. CBZ-H and CBZ-E had larger CVs than did CBZ (54.34 and 49.7
5 vs 35.15%, respectively, for total levels, and 50.31 and 54.46 vs 36
.22%, respectively, for free levels), as well as higher free fractions
. Determination of both total and free concentrations and free fractio
ns of CBZ and its metabolites, as well as their ratios, should provide
additional needed information for therapeutic drug monitoring of CBZ.