Pore pathway, vaginal

However, these general observations do not take into account the cyclical changes in the vaginal epithelium, which exert profound effects on vaginal absorption, especially for hydrophilic compounds. The permeability coefficient for the vaginal membrane (Pm) is equal to the sum of the permeability coefficient through the lipid pathway (P ) and the pore pathway (Pp) ... 

Fig. 5), the vaginal uptake of both alkanols and alka-noic acids also follows a first-order rate process and is dependent on the drug concentration in the vaginal fluid. The results agree well with a physical model that has a hydrodynamic diffusion layer in series with the mucosal membrane, that consists of two parallel pathways a lipoidal pathway and an aqueous pore pathway (Fig. 6). Immediately behind the mucosa (serosal side) a perfect sink is maintained by hemoperfusion. 

Penetration enhancers are low molecular weight compounds that can increase the absorption of poorly absorbed hydrophilic drugs such as peptides and proteins from the nasal, buccal, oral, rectal, and vaginal routes of administration [186], Chelators, bile salts, surfactants, and fatty acids are some examples of penetration enhancers that have been widely tested [186], The precise mechanisms by which these enhancers increase drug penetration are largely unknown. Bile salts, for instance, have been shown to increase the transport of lipophilic cholesterol [187] as well as the pore size of the epithelium [188], indicating enhancement in both transcellular and paracellular transport. Bile salts are known to break down mucus [189], form micelles [190], extract membrane proteins [191], and chelate ions [192], While breakdown of mucus, formation of micelles, and lipid extraction may have contributed predominantly to the bile salt-induced enhancement of transcellular transport, chelation of ions possibly accounts for their effect on the paracellular pathway. In addition to their lack of specificity in enhancing mem-... 

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