Effect of antihistamines on anaphylactoid oedema in rats using a modified plethysmometer for measuring foot volume

This study reports the quantitative effect of the H1--and H2--receptor antagonists on dextran-induced anaphylactoid oedema in rats. The findings indicate that mepyramine, promethazine and chlorpromazine which are H1--receptor antagonists significantly inhibited this anaphylactoid oedema. While on the other hand burimamide an H2--receptor antagonist at doses below 500 micrograms/kg inhibit dextran-induced oedema but at higher doses enhances oedema formation in the test rats. E.D50 values obtained for mepyramine, chlorpromazine and promethazine are 5.01 mg/kg, 0.36 mg/kg, 1.78 mg/kg respectively. The dual effects of burimamide on dextran-induced oedema merits further investigation and confirmation with the aid of other H1--and/or H2--receptor systems. A modification of the plethysmometric method of Buttle et. al. (1957) is also described.