Possible Interaction: Dextroamphetamine and Guanethidine

“ Dextroamphetamine and methamphetamine totally reversed the blocking action of guanethidine on the cold‐pressor response and simultaneously antagonized the hypotensive effect of guanethidine.”

“The effects of dextroamphetamine , methamphetamine, methylphenidate, nialamide, imipramine, and ephedrine in reversing the adrenergic neuron blocking action of guanethidine were investigated in 16 human hypertensive subiects, with the abolition of the cold‐pressor response and the fall of arterial blood pressure as evidence of the blocking action of guanethidine.”

“These observations suggest that hypertensive patients taking dextroamphetamine for weight reduction will respond poorly to guanethidine, and that dextroamphetamine and methamphetamine would serve as effective antagonists of guanethidine in clinical situations where the drug has caused an excessive fall in blood pressure.”

“ Dexamphetamine antagonized the sympathetic nerve block by guanethidine in the isolated hypogastric nerve-vas deferens preparation of the guinea-pig.”

“ Dexamphetamine antagonized the sympathetic nerve block by guanethidine in the isolated sympathetically innervated rabbit ileum; the evidence suggests that the antagonism was competitive.”

“Doses of dexamphetamine , larger than those required to antagonize the blocking action of guanethidine , abolished the responses of the nictitating membrane, ileum and vas deferens to nerve stimulation.”

“ Dexamphetamine and certain other indirectly acting sympathomimetic amines prevent or reverse the sympathetic nerve blocking action of guanethidine in anaesthetised cats and dogs.”

“In contrast, guanethidine (0·2 μg ml−1) produced a slow onset blockade which was completely reversed by (+)‐amphetamine.”

“6 Dexamphetamine both prevented and antagonized the neurone blockade and the subcellular noradrenaline‐depleting action of PEG and guanethidine.”

“4 It is suggested that the antagonism between dexamphetamine and guanethidine is due to a reduction in the uptake of guanethidine by the nerve endings rather than to interaction of the two drugs at the receptor site for the adrenergic neurone blocking action of guanethidine.”