Drug Interaction Report

Cimetidine and Labetalol: Interaction Details

A pharmacist-reviewed analysis of the Cimetidine and Labetalol interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Cimetidine

Tagamet
+

Labetalol

Normodyne® Trandate Trandate®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
LinkedIn
Interaction severity
Moderate
Can be significant — usually manageable with monitoring.
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.

Of 83 documented Cimetidine interactions, 22 are rated moderate — including this one.
Onset
rapid
Evidence
probable
Severity
Moderate

What happens

Increased labetalol serum levels, bradycardia, and hypotension

Interaction Deep Dive

Cimetidine has been reported to increase propranolol, metoprolol, and labetalol levels by as much as two-fold, but not atenolol, nadolol, or pindolol levels231. The clinical significance of the interaction is unknown because most studies report no changes in heart rate or blood pressure with concurrent cimetidine 435.

Why it happens (mechanism)

Decreased labetalol metabolism

Literature reports

1 report — tap to read

a) Concurrent use of cimetidine and labetalol resulted in increased labetalol serum levels, but there was no change in pharmacologic response. In a pharmacokinetic study of nine healthy subjects, concurrent use of oral cimetidine 300 mg four times daily and labetalol 200 mg twice daily resulted in a mean increase of 79% in the labetalol AUC (835 +/- 496 vs 1380 +/- 588 ng/hr/mL; P less than 0.05) and a significant increase in Cmax (274+/- 99 vs 356 +/-109 mg/mL; P less than 0.05). Systemic clearance decreased from 23.2 +/- 5.3 to 17.7 +/- 3.7 mL/min/kg (P less than 0.05). However, there were no significant changes in beta-blockade 1.

Common questions

Can I take Cimetidine and Labetalol together?

Increased labetalol serum levels, bradycardia, and hypotension Always confirm with your pharmacist or prescriber before making any change.

How serious is the Cimetidine and Labetalol interaction?

It is rated moderate. Can be significant — usually manageable with monitoring.

How quickly could this interaction happen?

The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.

How strong is the evidence for this interaction?

The evidence is graded "probable". Good supporting evidence, though not definitively proven.

From our Q&A

Real reader questions about these medications, each personally answered by our pharmacist:

Questions for your pharmacist

  • Does my dose of Cimetidine or Labetalol 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 (5)

  1. Lalonde RL, O'Rear TL, Wainer IW, et al: Labetalol pharmacokinetics and pharmacodynamics: evidence of stereoselective disposition. Clin Pharmacol Ther 1990; 48:509-519. PubMed
  2. Duchin KL, Stern MA, Willard DA, et al: Kinetic interactions of nadolol and propranolol with cimetidine. Br J Clin Pharmacol 1984a; 17:486-487. PubMed
  3. Mutschler E, Spahn H, & Kirch W: The interaction between H2-receptor antagonists and beta-adrenoceptor blockers. Br J Clin Pharmacol 1984; 17(suppl 1):51S-57S. PubMed
  4. Donn KJ, Powell JR, Rogers JF, et al: The influence of H2-receptor antagonists on steady-state concentrations of propranolol and 4-hydroxypropranolol. J Clin Pharmacol 1984; 24:500-508.
  5. Kirch W, Ramsch K, Janisch HD, et al: The influence of two histamine H2-receptor antagonists, cimetidine and ranitidine, on the plasma levels and clinical effect of nifedipine and metoprolol. Arch Toxicol Suppl 1984; 7:256-259. PubMed
Was this write-up helpful?
Cimetidine

Keep reading about Cimetidine

All Cimetidine interactions (83)
Also serious with: Dofetilide Colchicine Octreotide Injection Meloxicam Injection
Labetalol

Keep reading about Labetalol

All Labetalol interactions (215) Labetalol drug information
Also serious with: Methotrexate Methylergonovine Olodaterol Oral Inhalation Melatonin
Beyond drug–drug

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:

Cimetidine + Activated Charcoal Pu-erh Tea St. John's Wort Adrafinil African Wild Potato Banderol Beer Bitter Melon + 87 more
Labetalol + Activated Charcoal American Hellebore American Mistletoe Beer Indian Snakeroot Siberian Cocklebur Tyramine Wine + 168 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

Check another combination

Our instant two-drug interaction checker is almost here.

Coming soon

The instant two-drug checker is on its way.

In the meantime, browse the directory below to look up any drug and see its documented interactions.

Still have questions about this combination?

Every question gets a real answer from a licensed pharmacist — free, and usually within a day.

Ask the pharmacist
This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.