Biphasic effect of local anesthetic and beta-blocker heptacaine on fluidity of phosphatidylcholine bilayers as detected by ESR spin probe method.

Heptacaine (1), the monohydrochloride of [2-(heptyl-oxy)phenyl]-2-(1-piperidinyl)ethyl ester of carbamic acid, exerts a biphasic effect on the fluidity of egg yolk phosphatidylcholine (EYPC) model membranes as detected by the methyl esters of stearic acid spin probes with the paramagnetic doxyl group bound to the C-12 or C-16. The fluidity initially increases with an increase in the molar ratio of 1:EYPC, but a molar ratios above 1:EYPC = 0.5 a decrease of fluidity has been observed.