Foscarnet and Buprenorphine: 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
Buprenorphine
Foscarnet
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.
Both buprenorphine (a pain and addiction medicine) and foscarnet (an antiviral) can affect the timing of your heartbeat. On an ECG, this is called the QT interval. When two medicines that each stretch out this timing are taken together, the effects can add up. In rare cases, a very long QT can lead to a dangerous irregular heartbeat.
The good news is this is a possible risk based on how these drugs work, not something proven to happen often. Your care team can manage it by checking your heart rhythm, keeping your minerals (like potassium and magnesium) in balance, and deciding what is safest for you. Please talk with your pharmacist or doctor before making any changes.
Effect: Additive QT-interval prolongation from concurrent buprenorphine and foscarnet, both of which independently carry QT liability.
Direction/mechanism: Pharmacodynamic additive effect on cardiac repolarization; neither agent is dependent on the other's metabolism here. The magnitude of combined risk is not quantified.
- Onset: Unspecified.
- Evidence: Theoretical.
- Severity: Major.
Management: Avoid concomitant use where feasible. If co-administered, obtain baseline and follow-up ECGs, correct electrolytes (K+, Mg2+), and heighten caution with additional risk factors: bradycardia, CHF, recent AF cardioversion, digitalis therapy, congenital or baseline long QT.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Buprenorphine should not be taken together with medications known to lengthen the QT interval342. It remains unclear what risk arises when buprenorphine is paired with other agents that prolong the QT interval. When prescribing buprenorphine to patients who present with risk factors, including hypokalemia, bradycardia, recent conversion from atrial fibrillation, congestive heart failure, digitalis therapy, baseline QT prolongation, subclinical long-QT syndrome, or severe hypomagnesemia, clinicians should take these considerations into account in their decision making1.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Because both can lengthen the QT interval, your team may take steps to keep you safe.
- Your prescriber may check an ECG to watch your heart rhythm.
- Your team may check and correct blood minerals like potassium and magnesium.
- They may consider whether an alternative is a better fit, especially if you have heart risk factors.
Tell your pharmacist or doctor if you have heart rhythm problems, a slow heartbeat, or a family history of long-QT, and report fainting, dizziness, or palpitations right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Foscarnet and Buprenorphine together?
Buprenorphine and foscarnet can each prolong the QT interval, so combining them may add to that risk; talk with your care team, who can monitor your heart rhythm and electrolytes or choose an alternative. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Foscarnet and Buprenorphine 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 Foscarnet and Buprenorphine interaction managed?
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Because both can lengthen the QT interval, your team may take steps to keep you safe. Your prescriber may check an ECG to watch your heart rhythm. Your team may check and correct blood minerals like potassium and magnesium. They may consider whether an alternative is a better fit, especially if you have hea… 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 Foscarnet or Buprenorphine 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 (4)
- Product Information: BRIXADI(TM) subcutaneous extended-release injection, buprenorphine subcutaneous extended-release injection. Braeburn Inc (per FDA), Plymouth Meeting, PA, 2023. DailyMed
- Product Information: BUTRANS(R) transdermal system patch, buprenorphine transdermal system patch. Purdue Pharma L.P. (per FDA), Stamford, CT, 2016. DailyMed
- Product Information: BELBUCA(TM) buccal film, buprenorphine buccal film. Endo Pharmaceuticals Inc. (per FDA), Malvern, PA, 2016.
- Product Information: BUPRENEX(R) intravenous injection, intramuscular injection, buprenorphine HCl intravenous injection, intramuscular injection. Indivior Inc. (per DailyMed), Richmond, VA, 2016. DailyMed
Keep reading about Buprenorphine
Keep reading about Foscarnet
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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