SIMULTANEOUS MEASUREMENT OF NICOTINIC-ACID AND ITS MAJOR METABOLITE, NICOTINURIC ACID IN URINE USING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY- APPLICATION OF SOLID-LIQUID EXTRACTION

The concentrations of nicotinic acid (NiAc) and nicotinuric acid (NiUA c), a major metabolite of NiAc, were simultaneously determined in urin e using solid-phase extraction (cation-exchange extraction) and revers ed-phase high-performance liquid chromatography with ultraviolet detec tion. The intra- and inter-day precision studies showed good reproduci bilities: the coefficients of variations were less than 8.1% for NiAc and 8.8% for NiUAc. The calibration curves were linear (r(2)>0.9934) i n the concentration range 10-1000 mu g/ml. The removal of endogenous i nterferences in urine by solid-phase extraction presented here is supe rior to the pretreatment protocols reported previously by other worker s. The method was used in a preliminary pharmacokinetic study in rats after intravenous administration of NiAc (5 and 15 mg/kg).