Relugolix and Alfentanil: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Alfentanil
No brand names on recordRelugolix
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.
Alfentanil is a strong opioid pain medicine, and relugolix (Orgovyx) can speed up how fast your body breaks alfentanil down. That means the alfentanil may not work as well, so your pain could be less controlled. If your body has gotten used to the opioid, this faster clearing can even bring on withdrawal symptoms like sweating, chills, restlessness, or belly cramps.
Here is the reassuring part: your care team can handle this. They can adjust your alfentanil dose to keep you comfortable and watch how you are doing. Please do not change either medicine on your own. Just let your doctor or pharmacist know you take both.
Mechanism: Relugolix may induce CYP3A4, the enzyme responsible for alfentanil metabolism, lowering alfentanil exposure (AUC/Cmax). Neither drug is a prodrug, so the net effect is reduced opioid effect.
Direction/effect: Decreased alfentanil efficacy and possible opioid withdrawal in dependent patients.
Evidence: Theoretical; magnitude and onset unspecified. Severity rated major.
Management:
- If co-use is necessary, titrate alfentanil upward to stable effect.
- Monitor for inadequate analgesia and withdrawal signs.
- On discontinuing relugolix, alfentanil exposure rises; monitor closely and consider dose reduction to avoid respiratory depression.
What happens
Reduced ALfentanil exposure, reduced efficacy of ALfentanil and an increased risk of a withdrawal syndrome
Interaction Deep Dive
Taking ALfentanil together with CYP3A4 inducers can lower ALfentanil exposure, which may diminish its effectiveness or trigger a withdrawal syndrome in patients who have become physically dependent on ALfentanil. When such combined use cannot be avoided, an increase in the ALfentanil dose may be considered until stable drug effects are reached, and patients should be watched for indications of respiratory depression. Once a CYP3A4 inducer is discontinued and its effects gradually diminish, ALfentanil exposure will rise, potentially heightening or extending both the intended effects and the adverse reactions, and possibly producing serious respiratory depression. Close and frequent monitoring is warranted, along with consideration of reducing the ALfentanil dose1.
Why it happens (mechanism)
Induction of CYP3A4-mediated metabolism of ALfentanil
How to manage this interaction
Keep taking both medicines as prescribed unless your care team tells you otherwise. Here is what your team may do:
- Adjust and individualize your alfentanil dose so your pain stays controlled while you are on relugolix.
- Monitor you more closely for signs the opioid is not working or for withdrawal (sweating, chills, restlessness, cramps).
- Watch carefully when relugolix is stopped, since alfentanil levels can rise again; the dose may need lowering and they will watch for slowed breathing.
Tell your pharmacist or prescriber if your pain worsens, you feel withdrawal symptoms, or you become very drowsy or short of breath.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Relugolix and Alfentanil together?
Relugolix may speed up how your body clears alfentanil, weakening pain relief and risking withdrawal; your care team can manage this by adjusting the dose and monitoring you, especially when relugolix is started or stopped. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Relugolix and Alfentanil interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Relugolix and Alfentanil interaction managed?
Keep taking both medicines as prescribed unless your care team tells you otherwise. Here is what your team may do: Adjust and individualize your alfentanil dose so your pain stays controlled while you are on relugolix. Monitor you more closely for signs the opioid is not working or for withdrawal (sweating, chills, restlessness, cramps). Watch carefully when relugolix is stopped, since alfentanil… Management is individual — always follow your own care team's guidance.
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 Relugolix or Alfentanil 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 (1)
- Product Information: Alfentanil HCl intravenous injection, alfentanil HCl intravenous injection. Rising Pharma Holdings, Inc (per FDA), East Brunswick, NJ, 2025.
Keep reading about Alfentanil
Keep reading about Relugolix
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