Abstract: This invention relates to a method for improving the efficiency of a drug containing a free carboxy group, the improvement comprising esterifying said carboxy group to the hydroxy group of the glycerol portion of a glycerolphospholipid ester having the formula: or pharmaceutically acceptable salts thereof wherein one of R1 and R2 is hydrogen and the other is hydrogen, a hydrocarbyl fatty acid acyl group having 4-26 carbon atoms or a hydrocarbyl heteroatom fatty acid acyl group having 3-25 carbon atoms, or and R is a naturally occurring polar head group characteristic of a glycerophospholipid isolated from endogenous sources; R3 is hydrogen or lower alkyl and R4 is hydrogen, hydrocarbyl containing from 1-18 carbon atoms in a principal chain and up to a total of 23 carbon atoms, said principal chain may contain 1-5 double bonds or 1-2 triple bonds; phenyl which may be unsubstituted or substituted with lower alkyl; naphthyl which may be unsubstituted or substituted with low

Abstract: This invention relates to a method for improving the efficiency of a drug containing a free carboxy group, the improvement comprising esterifying said carboxy group to the hydroxy group of the glycerol portion of a glycerolphospholipid ester having the formula: ##STR1## or pharmaceutically acceptable salts thereof wherein one of R.sub.1 and R.sub.2 is hydrogen and the other is hydrogen, a hydrocarbyl fatty acid acyl group having 4-26 carbon atoms or a hydrocarbyl heteroatom fatty acid acyl group having 3-25 carbon atoms, or ##STR2## and R is a naturally occurring polar head group characteristic of a glycerophospholipid isolated from endogenous sources;R.sub.3 is hydrogen or lower alkyl andR.sub.