Effect of pH on Absorption of Acidic Drugs outside membrane inside In a low pH(acid)environment(e.g. stomach): ·[H+is high HA H++A .'[HA]increases HA HA .'drug absorption increases In a high pH(basic)environment (e.g. small intestine): ·H+is low H++A HA H++A- A ,'.IA】increases .'drug absorption decreases