Pharmacokinetics of oral glycerol-1-nitrate

The plasma kinetics and urinary excretion of glycerol-1-nitrate (G-1-N), a water soluble metabolite of glycerol trinitrate with anti-anginal potential, have been investigated in healthy human volunteers following oral doses of 10, 20 and 40 mg tablets and 20 mg as drops. In all volunteers G-1-N was rapidly absorbed. The mean concentration-time curves peaked 40 min after administration of tablets at 144 ng/ml (10 mg), 308 ng/ml (20 mg) and 573 ng/ml (40 mg). After the drops the peak of 324 ng/ml occurred at 1 h. The areas under the G-1-N concentration-time curve and the G-1-N peak heights were linear with dose. Tablets and drops can be regarded as bioequivalent with respect to area under the curve and elimination half-life. The bioavailability of the 20 mg tablet relative to the 20 mg drops was 98.6% in terms of area under the curve. The mean apparent half-life of G-1-N elimination from plasma was 2.69 +/- 0.67 h (n = 46). The mean residence time of G-1-N in the body was 4.65 h compared to 0.28 h for glycerol trinitrate after buccal administration. Female volunteers were found to have significantly lower areas under the curve than male volunteers. The difference was probably due to differences in body weight. Renal excretion does not play an important role in the elimination of oral G-1-N from the body. An overall average of 5.42% of the G-1-N dose was excreted in the urine; free drug accounted for 4.02% and conjugated drug for 1.40%.