The present invention relates to the formulations of ester derivatives of capsaicin and ester derivatives of myristoleic acid. These derivatives are capable of reverting to the active parent compound following enzymatic or chemical hydrolysis. These derivatives have a higher lipophilicity, lipid solubility and less irritation to the skin than the parent compound, and hence are better able to be incorporated into certain pharmaceutical formulations, including cream and ointment pharmaceutical formulations. The pharmaceutical compositions of the present invention contain a compound of following formula (Ia): R—CO-CAP  (Ia) wherein CAP refers to collectively the capsaicins represented in FIG. 1 and a compound of formula (Ib): MCO-O—R  (Ib) wherein MCO refers to myristoleic acid. In formulae Ia and Ib, R is selected from alkyl groups of up to about 18 carbon atoms and aryl groups of up to about 18 carbon atoms and alkylene group of up to about 18 carbon atoms and an arylene group of up to about 18 carbon atoms. The alkyl, aryl and alkylene groups may be substituted or un-substituted, branched or straight chains. In addition, R may contain heteroatoms and may be straight chained or branched. The pharmaceutical compositions containing compounds of formulae Ia and Ib are useful for pain management in mammals in vivo and have been contemplated to be used in the treatment of various pains in humans.
Esters of capsaicin for treating pain