Pharmacokinetic disposition of isoxicam in hepatic cirrhosis

To determine the effect of liver dysfunction on the absorption and disposition of isoxicam, we administered a single oral dose of 200 mg to 8 patients with alcoholic cirrhosis, and followed the plasma concentration-time curve for 96 h. The calculated isoxicam disappearance t 1/2 of 30 +/- 19.1 h in these patients was not different from the mean value of 31 +/- 5.7 h obtained in 10 normal subjects studied earlier by our group; however, interindividual variation was larger. No differences in lag time (0.42 +/- 0.3 vs 0.49 +/- .2 h) or time to peak concentration (9.0 +/- 2.5 vs 10.0 +/- 2.9 h) were observed. However, the peak plasma isoxicam concentrations and the areas under the plasma concentration-time curves (AUC) were reduced 32% (p less than 0.01) and 41% (p less than 0.01), respectively. Plasma protein binding of isoxicam studied by equilibrium dialysis was 80 +/- 16% in the cirrhotic patients compared with 96 +/- 1.4% in the normal volunteers (p less than 0.02), again with larger interindividual variation noted in patients with cirrhosis. The binding did not correlate significantly with any laboratory tests of liver function or with the AUC for plasma isoxicam. As compared to the normal subjects, these cirrhotic patients had decreased plasma isoxicam binding, peak plasma isoxicam concentrations and AUC, without a significant change in the apparent disappearance half-life of total plasma isoxicam after a single oral dose.