Determinants of response to intravenous hydralazine in hypertension

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Abstract
There is marked interindividual variation in hypotensive response to i.v. hydralazine (H). The determinants of response were examined in patients with hypertension. After a single i.v. dose of 0.3 mg/kg H, response was correlated independently (r = 0.8364) with both predrug blood pressure and acetylator index (AI). I.v. dose ranging studies showed that response also depended on the amount of H in the systemic circulation. Plasma H levels depend on AI after oral doses, but not after i.v. administration. AI affects response to H by an alternative, presumably nonmetabolic mechanism which, after oral dosing, would add to its effect on H levels. Response to i.v. nitroprusside was not related to AI, perhaps indicating specificity of this effect for H. Determining AI before giving H to a patient is useful.