Synthesis and evaluation of some acyloxyethyl mefenamates as possible prodrugs

Various acyloxyethyl mefanamates were synthesized and evaluated for potential application as prodrugs. Their kinetics of hydrolysis were examined in aqueous solutions of pH 1.0 and 7.4 and in human plasma at 37 degrees C. Among the synthesized compounds, the beta-carboxypropionylethyl mefenamate and the pivaloyloxyethyl mefenamate show high stability against enzymatic and non enzymatic hydrolysis. On the other hand the acetyloxyethyl mefenamate shows t1/2s of 1.4 h, 1.41 h and 3.61 h in human plasma, solutions of pH 7.4 and pH 1.0 respectively; However, its hydrolysis to mefenamic acid in plasma was not quantitative. Preliminary in vivo study shows that acetyloxyethyl mefenamate gave plasma concentration of mefenamic acid lower than that of control after oral administration. The calculated AUC0-inf for the acetyloxyethyl and control were 45 and 85 micrograms.h/ml respectively.