Hydralazine and Metoprolol: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Hydralazine
Metoprolol
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased metoprolol concentrations
Interaction Deep Dive
HydrALAZINE increases the oral bioavailability of metoprolol; this interaction occurs more frequently in a fasting state and does not occur with sustained-release beta-blockers14. Concomitant use of hydrALAZINE and metoprolol may cause inhibition of presystemic metabolism of metoprolol by hydrALAZINE, resulting in increased metoprolol bioavailability and metoprolol levels. HydrALAZINE is also a CYP2D6 inhibitor, which may increase plasma concentrations of metoprolol, leading to decreased cardioselectivity 23. If concurrent therapy is required, monitor blood pressure carefully.
Why it happens (mechanism)
Inhibition of presystemic metabolism of metoprolol and inhibition of CYP2D6-mediated metabolism of metoprolol by hydrALAZINE
Literature reports
1 report — tap to read
a) Concomitant administration of oral metoprolol 50 mg twice daily and oral hydrALAZINE 25 mg twice daily resulted in significant increases (38%) in the median area under the plasma concentration-time curve (AUC) for metoprolol in 10 hypertensive pregnant women. Metoprolol Cmax levels were increased by 88%, and the Tmax was decreased from 1.5 to 1 hour. No effect on plasma levels of alpha-hydroxymetoprolol were observed, suggesting that the mechanism of this interaction is primarily related to a reduction in the hepatic first-pass elimination. No significant increases in the metoprolol serum levels occurred if the baseline levels were high during monotherapy. The hydrALAZINE effect on the metoprolol serum levels was of short duration (2 to 3 hours) in most of the patients. This interaction should not be clinically significant for this patient population 1.
Common questions
Can I take Hydralazine and Metoprolol together?
Increased metoprolol concentrations Always confirm with your pharmacist or prescriber before making any change.
How serious is the Hydralazine and Metoprolol interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Hydralazine or Metoprolol need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (4)
- Lindeberg S, Holm B, Lundborg P, et al: The effect of hydralazine on steady-state plasma concentrations of metoprolol in pregnant hypertensive women. Eur J Clin Pharmacol 1988; 35:131-135. PubMed
- Product Information: Lopressor(R) oral tablets, metoprolol tartrate oral tablets. Validus Pharmaceuticals, LLC (per FDA), Parsippany, NJ, 2013. DailyMed
- Product Information: Lopressor(R) intravenous injection, metoprolol tartrate intravenous injection. Novartis Pharmaceuticals Corporation (per FDA), East Hanover, NJ, 2013. DailyMed
- Schafer-Korting M & Mutschler E: Pharmacokinetics of bendroflumethiazide alone and in combination with propranolol and hydralazine. Eur J Clin Pharmacol 1982; 21:315-323. PubMed
Keep reading about Hydralazine
Keep reading about Metoprolol
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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