Hydralazine is a direct arteriolar vasodilator used for hypertension and heart failure. The A-HeFT trial demonstrated significant mortality benefit when combined with isosorbide dinitrate (BiDil) in self-identified Black patients with heart failure. Also used for hypertensive emergencies in pregnancy.
Evidence rating strong. Most-documented uses: reduces mortality in black patients with hfref (a-heft, combined with isdn), direct arteriolar vasodilation reduces afterload, safe in pregnancy for hypertension management. 10 sources indexed (2003–2025), with 1 interaction record on file.
The science
How it works, mechanistically.
Core mechanism
Directly relaxes arteriolar smooth muscle through incompletely understood mechanisms, possibly involving interference with calcium transport, increased nitric oxide release, or activation of potassium channels. Reduces peripheral resistance without significant venous dilation. Causes reflex tachycardia and increased cardiac output. Combined with nitrates, the hydralazine-nitrate combination improves NO bioavailability by scavenging reactive oxygen species.
Class
Direct Arteriolar Vasodilator
Absorption
Water-soluble; take with food
Dosing
Dosing & protocol.
Common range
25–100 mg 2–3 times daily (HF combination: 37.5 mg three times daily with ISDN) (as prescribed by your physician)
Recommended form
Oral tablet or IV/IM injection
Food enhances bioavailability; undergoes extensive first-pass hepatic metabolism via acetylation (metabolism rate depends on acetylator phenotype)
Depletions
What it depletes.
Nutrients this medication can lower over time, and what to replace.
Vitamin B6
Moderate
Hydralazine can antagonize pyridoxine metabolism and has been linked to pyridoxine-deficiency neuropathy during prolonged therapy.
Replace PyridoxineMonitor Clinical neuropathy assessment + plasma PLP if availableOnset Usually with high-dose or prolonged therapy
Long-term hydralazine can interfere with vitamin B6 biology and has caused pyridoxine-deficiency neuropathy in case reports. Vitamin B6 can help prevent or correct deficiency-related nerve symptoms when hydralazine is the cause. Very high-dose B6 can also cause neuropathy, so replacement should stay in a conservative range unless supervised.
Recommendation: If you take hydralazine long term, ask your prescriber whether low-dose vitamin B6 is appropriate, especially if you develop numbness, tingling, burning, or poor dietary intake. Avoid chronic high-dose B6 unless directed and monitored.
Govindasamy V, Kamel MA, Volucke G et al.. Efficacy and Safety of Nifedipine Compared to Intravenous Hydralazine for Severe Hypertensive Disorders in Pregnancy: A Systematic Review and Meta-Analysis of Randmomized Controlled Trials. Medical sciences (Basel, Switzerland). 2025
Gonçalves OR, Bendaham LCAR, Simoni GH et al.. Comparative efficacy and safety between intravenous labetalol and intravenous hydralazine for hypertensive disorders in pregnancy: A systematic review and meta-analysis of 19 randomized controlled trials. European journal of obstetrics, gynecology, and reproductive biology. 2024
Farag M, Mabote T, Shoaib A et al.. Hydralazine and nitrates alone or combined for the management of chronic heart failure: A systematic review. International journal of cardiology. 2015
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