Effect of innate lipid solubility on buccal absorption of basic drugs

This study is designed, to find out the effect of innate lipid solubility on buccal absorption of basic drugs with similar pka values. Allopurinol hydrochloride, nortriptyline hydrochloride and procainamide hydrochloride with Pka values 9.4, 9.7 and 9.2 respectively were selected for in vivo (buccal absorption test) and in vitro (I-octanol/buffer partitioning coefficient) study at pH range 6-10. Results found that the mean percentage of buccal partitioning and/I-octanol partitioning of allopurinol hydrochloride was decreased with the increase in pH from 6.0-l0. On the other had mean percentage of buccal partitioning and I-octanol partitioning of procainamide hydrochloride and nortriptyline hydrochloride was increased with the increase in pH from 6.010. It is concluded that although the drugs studied have nearly similar Pka values their lipid solubility is widely variable. A good correlation between buccal and I-octanol partitioning excluded the possibility of interaction between these drugs and I-octanol. Decrease in lipid solubility of allopurinol hydrochloride with increase in pH needs further evaluation