Effects of chronic ethanol ingestion on tissue elimination-phase kinetics of procainamide in rats

The effects of chronic ethanol ingestion on the pharmacokinetics of procainamide in various tissues were studied. Ethanol-treated rats received ethanol at 4 g/kg/day for an initial 7 days and then at 8 g/kg/day for the subsequent 21 days; control rats received isocaloric sucrose. After a single intravenous dose, the semilogarithmic procainamide concentration-time profiles observed in hearts and kidneys of both groups of rats were similar to the previously reported biexponential profiles of procainamide concentration in blood. This finding indicates a rapid distribution equilibrium of drug in both blood and these highly perfused tissues. The profiles of drug concentration in thigh muscle and fat of both groups of rats exhibited a drug-uptake phase during the initial 25-min period followed by a monoexponential decline in drug concentration. For all tissues, the slopes (beta values) of the curves of the drug concentration versus time were calculated on the basis of elimination-phase data, except for fat of control rats where the predominant elimination phase was not discernible. The beta values in hearts and thigh muscles of ethanol-treated rats were significantly higher than those in the corresponding tissues of control rats. These results are evaluated in light of previously reported effects of the same ethanol treatment on the distribution pharmacokinetics and the steady-state partition coefficients of the drug in these tissues. Possible mechanisms are proposed to account for these effects on the basis of the known diverse effects of chronic ethanol ingestion on the cellular compositions of individual organs and tissues.