Drug Interaction Report

Rifampin and Diazepam Rectal: Interaction Details

A pharmacist-reviewed analysis of the Rifampin and Diazepam Rectal 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

Rifampin

Rifadin
+

Diazepam Rectal

Diastat Diastat®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close 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 176 documented Rifampin interactions, 130 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
delayed
Evidence
theoretical
Severity
Major

What happens

Reduced diazePAM exposure

Interaction Deep Dive

Exert caution with coadministration of rifAMPin with drugs metabolized by cytochrome P4501. In a controlled study, the addition of rifAMPin to diazePAM treatment decreased the diazePAM half-life from 58 hours to approximately 14 hours 4. Patients also appeared to eliminate the desmethyldiazePAM metabolite more rapidly (halazepam, clorazepate, and prazepam have a desmethyldiazePAM metabolite) 5. Coadministration of rifAMPin (inducers of CYP3A4 and CYP2C19) and diazePAM (substrates of CYP3A4 and CYP2C19) may reduce diazePAM exposure 231.

Why it happens (mechanism)

Increased hepatic metabolism; induction of CYP3A4-mediated metabolism of diazePAM; induction of CYP2C19-mediated metabolism of diazePAM

Literature reports

1 report — tap to read

a) In a controlled study, the addition of rifAMPin to diazePAM treatment decreased the diazePAM half-life from 58 hours to approximately 14 hours 4. Patients also appeared to eliminate the desmethyldiazePAM metabolite more rapidly (halazepam, clorazepate, and prazepam have a desmethyldiazePAM metabolite) 5.

Common questions

Can I take Rifampin and Diazepam Rectal together?

Reduced diazePAM exposure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Rifampin and Diazepam Rectal interaction?

It is rated major. Potentially serious — often needs a change or close monitoring.

How quickly could this interaction happen?

The documented onset is "delayed". Effects tend to build up gradually over days to weeks.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

  • Does my dose of Rifampin or Diazepam Rectal 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)

  1. Product Information: RIFATER(R) oral tablets, rifampin, isoniazid, pyrazinamide oral tablets. sanofi-aventis US LLC (per FDA), Bridgewater, NJ, 2023. DailyMed
  2. Product Information: RIFADIN(R) IV intravenous injection, rifampin intravenous injection. sanofi-aventis US LLC (per FDA), Bridgewater, NJ, 2023. DailyMed
  3. Product Information: RIFADIN(R) oral capsules, rifampin oral capsules. sanofi-aventis US LLC (per FDA), Bridgewater, NJ, 2023. DailyMed
  4. Ochs HR, Greenblatt DJ, & Roberts GM: Diazepam interaction with antituberculosis drugs. Clin Pharmacol Ther 1981b; 29:671-678. PubMed
  5. Ohnhaus EE, Brockmeyer N, Dylewicz P, et al: The effect of antipyrine and rifampin on the metabolism of diazepam. Clin Pharmacol Ther 1987; 42:148-156. DOI
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Rifampin

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All Rifampin interactions (176)
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Diazepam Rectal

Keep reading about Diazepam Rectal

All Diazepam Rectal interactions (281) Diazepam Rectal drug information
Also serious with: Isocarboxazid Flumazenil Ensitrelvir Zuranolone
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:

Rifampin + Activated Charcoal Apple Asarabacca Beer Grapefruit Siberian Cocklebur St. John's Wort Sweet Orange + 214 more

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

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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.