Transport of organic ions through lipid bilayers

Abstract

In a previous article [Naunyn-Schmiedeberg's Arch Pharmacol (1981) 316:266-272] transport of a number of organic ions across lipid bilayers was investigated using single bilayer liposomes. In this investigation the translocation of structurally closely related barbiturates across lipid bilayers is studied. The anionic form of the barbiturates can pass lipid bilayers, provided that the lipophilicity of the 5,5-disubstituted side chain is high enough. This permeability of barbiturates in the ionized form explains their uncoupling action of the oxidative phosphorylation and the deviations from the pH-partition theory found in absorption processes.

Renal Excretion of Drugs and Other Xenobiotics

“…Finally, since the xenobiotic will cross cellular membranes pre ferentially in its undissociated form, its pKa will indicate the proportion of undissociated moiety at a given pH. The dissociated form may also diffuse across lipidic membranes to some extent if the structure of the molecule is such that its lipophilic properties mask its charged character [111].…”