High pressure liquid chromatographic assay of 4-methylpyrazole. Measurements of plasma and urine levels.

4-Methylpyrazole (4-MP), a potent competitive inhibitor of alcohol dehydrogenase activity, has potential usefulness as a treatment means for methanol and ethylene glycol poisoning as well as severe disulfiram-ethanol interactions. Further study of the safety and metabolism of 4-MP in human subjects is needed before it can be used in such therapies. An HPLC assay has been developed to measure 4-MP levels in plasma and urine samples. The method was sensitive enough to quantitate 4-MP in an amount as low as 0.1 nmol. Recovery of 4-MP from spiked urine and plasma samples was greater than 90%. 4-MP levels in the plasma and urine of rats injected with an oral dose of 50 mg/kg of body weight were determined; the detectability limit in these samples was about 3 microM. The method is easy to perform and thus has practical application for research laboratories dealing with ethanol metabolism and clinical laboratories desiring to monitor 4-MP levels.