Buccal permeation of buspirone: mechanistic studies on transport pathways.

The transport of buspirone across porcine buccal mucosa in vitro was investigated to elucidate the mechanisms of transport and permeation enhancement. The apparent permeability increased with an increase in pH to a lesser degree than the dependence of the partition coefficient. Whereas the lipophilic or apparent transcellular pathway was found to be the dominant buccal transport route for buspirone, ionized species contributed significantly to transport at acidic pH. At neutral pH, bile salts did not increase the flux of the lipophilic species of buspirone, and in contrast to its effect on stratum corneum, aqueous propylene glycol alone did enhance the flux of buspirone across buccal mucosa in vitro. The use of an enhancer combination containing 5% oleic acid, 40% propylene glycol in buffer resulted in the greatest flux, and this was consistent with the effect of this combined enhancer on the flux of lipophilic drugs across stratum corneum and the dominance of the transcellular pathway for buspirone at neutral pH.