Halothane and Labetalol: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Halothane
No brand names on recordLabetalol
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
Hypotension or decreased cardiac output
Interaction Deep Dive
Concurrent use of labetalol and halothane has caused significant hypotension and cardiac depression when the halothane concentration was 3%2341. Beneficial hypotension has been induced without myocardial depression with 1% halothane concentrations 5.
Why it happens (mechanism)
Additive hypotensive and cardiodepressant effects
Literature reports
1 report — tap to read
a) A 49-year old woman with chronic renal failure received labetalol 800 mg daily, hydralazine 50 mg daily, and diazepam as preoperative medication for a kidney transplant. The patient had a history of myocardial infarction 18 months previously, followed by left heart failure, but no evidence of damage was seen on the preoperative electrocardiogram. Anesthesia was induced with intravenous atropine 0.6 mg, intravenous fentanyl 100 mcg, nitrous oxide, oxygen, and 0.5% halothane. Tubocurarine 20 mg was also given to provide muscular relaxation. Ten minutes after induction of anesthesia, complete heart block developed. Atropine 1.8 mg was given and halothane was discontinued, but the pulse rate continued to slow and asystole developed. A post-mortem examination revealed a posterior myocardial infarction two to three days prior to the anesthesia. The author suggests the possibility that in patients with previous myocardial damage, synergistic effects such as heart block may be more likely to occur between halothane and labetalol 1.
Common questions
Can I take Halothane and Labetalol together?
Hypotension or decreased cardiac output Always confirm with your pharmacist or prescriber before making any change.
How serious is the Halothane and Labetalol interaction?
It is rated major. Potentially serious — often needs a change or close 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 Halothane 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 a safer alternative to one of these medications for me?
References (5)
- Hunter JM: Synergism between halothane and labetalol. Anaesthesia 1979; 34:257-259. PubMed
- Scott DB, Buckley FP, Drummond GB, et al: Cardiovascular effects of labetalol during halothane anaesthesia. Br J Clin Pharmacol 1976; 3:817S-821S.
- Scott DB, Buckley FP, Littlewood DG, et al: Circulatory effects of labetalol during halothane anaesthesia. Anaesthesia 1978; 33:145-156. PubMed
- Scott DB: The use of labetalol in anaesthesia. Br J Clin Pharmacol 1982; 13(suppl 1):133S-135S. PubMed
- Toivonen J, Virtanen H, & Kaukinen S: Deliberate hypotension induced by labetalol with halothane, enflurane or isoflurane for middle-ear surgery. Acta Anaesthesiol Scand 1989; 33:283-289. PubMed
Keep reading about Halothane
Keep reading about Labetalol
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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