Analgesic Activity of Novel GABA Esters after Transdermal Delivery.

Analgesic activity of novel GABA esters with l-menthol (1), thymol (2), carvacrol (3) and guaiacol (4) was investigated by pharmacological models of thermal and chemical stimuli in mice after topical application in an ointment (2% w/w). The initial terpenes - l-menthol (5), thymol (6), carvacrol (7) and guaiacol (8) have also been studied under the same experimental conditions. All studied compounds were found to produce an antinociceptive effect in both thermal- and chemical-induced models of acute pain after their topical application. In the hot plate test, compound 1 demonstrated maximum analgesic activity and attenuated acute pain more than the reference drug BZC. GABA esters with l-menthol (1) and carvacrol (3), as well as l-menthol (5) itself exhibited analgesic activity which is the same or better in comparison with benzocaine in chemical-stimulated models of pain caused by either formalin or capsaicin.