Absorption and excretion of drugs. XXXIX. The absorption of isonicotinic acid derivatives from the skeletal muscle of the rats.

Abstract

Aqueous solutions of seven isonicotinic acid derivatives were injected to the hind leg of rats and the intramuscular absorption was followed by the local clearance method for a period of 5 min under the conditions in which the constant body temperature and smaller injection volume were maintained. Drug absorption is proportional to the amount remaining in the injection site, and both molecular weight and partition coefficient of drugs affect the intramuscular absorption. The observation presented here supported the conclusion that (1) the abscrption of unionized drugs from the injection site was chiefly proceeded by the apparent first order process and (2) the diffusion through the pores of the capillary vessels was predominant compared with the penetration through the capillary endothelial cells. In the case of ionized drugs, there was evidence that the absorption of a drug was influenced by the factor other than the above.