Effect of alphamethyldopa and of phenobarbitone on angiotensin responsiveness and renin activity in man.

Changes of angiotensin sensitivity and renin activity were studied in 25 subjects after one week's administration of alphamethyldopa, phenobarbitone and both compounds. The increase of angiotensin sensitivity produced by alphamethyldopa is abolished by the simultaneous administration of phenobarbitone, moreover angiotensin sensitivity rather decreases. Peripheral renin activity does not change in either of the cases. Phenobarbitone per se does not affect either angiotensin sensitivity or plasma renin activity. Possible mechanisms of the phenomenon are outlined. It is also concluded that angiotensin sensitivity may change considerably without detectable alteration of plasma renin sensitivity.