Effect of pH on Absorption of Basic Drugs outside membrane inside In a low pH (acid)environment (e.g. stomach): ·H+is high H++B HB* .[BH]increases H++B B .'drug absorption decreases In a high pH(basic)environment(e.g. small intestine): [H+]is low HB* H++B HB+ HB ,∴.[increases .'drug absorption increases