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It is a directly acting arteriolar vasodilator with little action on venous capacitance vessels; reduces total peripheral resistance and thus corrects a primary abnormality of hypertension. It causes greater reduction of diastolic than systolic BP, causes reflex tachycardia and therefore is often combined with b blockers to null each others side effects.


Moderate to severe hypertension not controlled by the first line drugs. Hypertension with renal involvement.


25-50 mg once to thrice daily.


Pregnancy, elderly, Ischaemic heart disease, tachycardia, aortic or mitral stenosis, dissecting aortic aneurysm, idiopathic, constrictive pericarditis.

Special Precautions

Liver impairment, severe renal failure, lactation, coronary or cerebrovascular disease. Abrupt withdrawal. Paediatrics: Reduce dose necessary. Pregnancy: Safety not established. Lactation: Drug passes into breast milk. Elderly: No special problem reported.

Side Effects

Facial flushing, throbbing, headache, dizziness, palpitation, nasal stuffiness. Paresthesias, tremors, muscle cramps, edema, lupus erythematosus or rheumatoid arthritis like symptoms.

Drug Interactions

Tricyclic antidepressents and monoamine oxidase inhibitors may increase the effects of hydralazine. Adrenaline enhances cardiac accelerating effect.

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