Observations on and pharmacokinetic discussion of percutaneous absorption of mefenamic acid

Abstract

Percutaneous absorption of a non-steroidal anti-inflammatory drug, mefenamic acid, was investigated biopharmaceutically using rabbits. The presence or absence of absorption was examined in simple ointment, macrogols ointment, hydrophilic ointment and absorptive ointment, which are listed in the Japanese Pharmacopeia. Favorable absorption was observed in the case of hydrophilic ointment, and it was also revealed that the volume of the intracutaneous reserve was large. p]The effects of the concentration of mefenamic acid, site of application, area of application and of additives in the ointments on acceleration of absorption were studied. When the concentration of mefenamic acid was more than 4.2%, the absorption was favorable. When the ointment was applied to the thigh, abdomen and back in that order, the amount of absorption increased. Although the amount of absorption increased with an increase in the area of application, no definite relationships could be found between the area of application and the amount of absorption. Concerning the additives, nicotinamide and N-methyl-2-pyrrolidone showed a favorable effect to accelerate absorption. The fraction of drug absorbed to the total drug (F) after intrarectal administration of hydrophilic ointment and absorptive ointment was compared with those after oral administration and percutaneous absorption.