Antagonism of adrenergic neuron blockade in hypertensive subjects

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Abstract
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. Dextroamphetamine and methamphetamine totally reversed the blocking action of guanethidine on the cold‐pressor response and simultaneously antagonized the hypotensive effect of guanethidine. Nialamide, methylphenidate, and ephedrine had a similar but less pronounced effect. The probable mechanism of this antagonism is discussed. Imipramine did not reverse the circulatory guanethidine effect. 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.