Spectrofluorimetric determination of vigabatrin and gabapentin in urine and dosage forms through derivatization with fluorescamine

A stability-indicating, sensitive, simple and selective spectrofluorimetric method was developed for the determination of vigabatrin (VG) and gabapent in (GB). The method is based on the reaction between the two drugs and fluo rescamine in borate buffer of pH 8.2 to give highly fluorescent derivatives that are measured at 472 nm using an excitation wavelength of 390 nn for b oth drugs. The optimum conditions were ascertained and the method was appli ed for the determination of VG and GB over the concentration range of 0.20- 4.00 and 0.1-1.0 mug/ml, respectively with detection limits of 0.05 mug/ml (2.9 x 10(-7) M) and 0.06 mug/ml (2.3 x 10(-7) M) for VG and GB, respective ly. The suggested method was applied, without any interference from the exc ipients, to the determination of the two drugs in their pharmaceutical form ulations. Furthermore, the method was extended to the in-vitro determinatio n of both drugs in spiked human urine. Interference from endogenous amino a cids could be eliminated through selective complexation with copper acetate , the % recovery (n = 4) is 98.0 +/- 7.05. Co-administered drugs such as la motrigine, phenobarbitone, valproic acid, clopazam, carbamazepine, clonazep am and cimitidine did not interfere with the assay. The method is also stab ility-indicating; as the degradation product of vigabatrin: 5-vinylpyrrolid in-2-one, produced no interference with its analysis. (C) 2002 Elsevier Sci ence B.V. All rights reserved.