Possible ion-pair-mediated absorption of mixidine I: partitioning and lethality studies.

Mixidine, a very soluble base which is completely ionized in all physiological fluids, was found to form ion-pairs as demonstrated by its ability to partition into 1-butanol from acidic solutions. A similar relationship was observed for the effect of acids on the absorption of intraduodenally and orally administered solutions of mixidine in rats (as determined by lethality). Studies also demonstrated that the pH-lethality effects were not specific for a particular counterion. Mixidine was more lethal when administered intraduodenally than when administered orally, and the counterions per se were not lethal in the doses used.