Abstract
A reversed phase ion pair HPLC method with UV detection has been developed for the determination of clavulanic acid (CVA) in human urine, taking solvent effects on detection wave length and on retention behavior on a hydrophobic stationary phase into account. The addition of tetrabutylammonium bromide (TBAB) to aqueous methanol containing phosphate buffer salts facilitated the detection of CVA at an accessible UV wave length, and also allowed the specific separation of CVA from endogenous urinary components.
The time courses of urinary excretion rate for intact CVA, amoxicillin (AMPC), and the latter's metabolites Denicilloic acid (AMPA) and penamaldic acid (AMPM) 3 following oral doses of BRL25000 or each of CVA and AMPC separately to healthy human subjects were determined by the established HPLC method. The statistical moment analysis of the time course curves indicated that when CVA was dosed in combination with AMPC, 27 to 45% of the dosed amount (125 mg) of CVA was excreted in the urine as the intact form with the mean residence time (MRT) ranging of 1.6 to 2. 1 hours after administration, while the corresponding values for AMPC were 56 to 73%(including metabolites) and 2.0 to 2.6 hours (for intact AMPC). These results indicate that CVA may undergo less absorption (and/or a greater degree of metabolism and extraurinary excretion) and faster urinary excretion than that of AMPC. From comparison of these results with those obtained after administration of individual doses of CVA and AMPC to the same subjects, it was found that there was no appreciable pharmacokinetic interaction between CVA and AMPC ascribable to the combination dose, although the analysis of variance indicated that the difference in the excreted amount of AMPM between individual and combined doses was significant at the 5% level.
