Cobicistat and Amitriptyline: 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
Amitriptyline
Cobicistat
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.
Here's what's going on. Your body uses an enzyme called CYP2D6 to break down amitriptyline. Cobicistat slows that enzyme down, so amitriptyline can build up higher than expected in your blood. That means the usual side effects of amitriptyline, like drowsiness, dry mouth, constipation, dizziness, or an irregular heartbeat, could become stronger.
This is based mostly on how the drugs work rather than lots of real-world cases, so please don't worry. Don't stop or change either medicine on your own. Your care team can manage this easily by starting low, checking your blood levels if needed, and adjusting your dose so you stay safe and comfortable.
Mechanism: Cobicistat inhibits CYP2D6, the primary pathway clearing amitriptyline (an active drug, not a prodrug). Result: increased amitriptyline exposure (higher AUC/Cmax), pronounced in CYP2D6 poor metabolizers.
Direction: Increased TCA effect and toxicity risk (anticholinergic effects, sedation, orthostasis, QRS/QT-related cardiotoxicity).
- Evidence: Theoretical; magnitude not quantified.
- Onset: Unspecified.
- Management: Use lowest feasible initial/maintenance dose, titrate carefully to effect, monitor clinically, and consider measuring amitriptyline plasma levels. Reduce dose if warranted. If cobicistat is discontinued, a dose increase may be needed.
What happens
Increased exposure of amitriptyline
Interaction Deep Dive
Taking amitriptyline (a CYP2D6 substrate) together with cobicistat (a CYP2D6 inhibitor) can raise amitriptyline exposure, particularly among poor metabolizers. Should combined use be necessary, proceed cautiously and keep the patient under close observation. It is also advisable to check amitriptyline plasma concentrations and lower the dose when warranted. Discontinuation of cobicistat may make it necessary to raise the amitriptyline dose1. When cobicistat is given alongside TCAs like amitriptyline, it is recommended to titrate the antidepressant dose carefully toward the intended effect, employing the lowest practical starting or maintenance dose, while monitoring the antidepressant response 2345.
Why it happens (mechanism)
Inhibition of CYP2D6-mediated metabolism of amitriptyline
How to manage this interaction
The good news: this is very manageable when your care team knows you take both.
- Keep taking both medicines exactly as prescribed unless your prescriber tells you otherwise.
- Your team will typically start amitriptyline at the lowest reasonable dose and titrate slowly to the effect you need.
- They may check amitriptyline blood levels and adjust the dose based on results.
- They will watch for side effects like heavy drowsiness, dry mouth, constipation, dizziness on standing, or heart rhythm changes.
- If cobicistat is ever stopped, your amitriptyline dose may need to be raised.
Report new or worsening side effects to your pharmacist or prescriber.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Cobicistat and Amitriptyline together?
Cobicistat can raise amitriptyline levels by blocking its breakdown, which may increase side effects; your care team can manage this by starting low, monitoring you, and adjusting the dose as needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Cobicistat and Amitriptyline 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 Cobicistat and Amitriptyline interaction managed?
The good news: this is very manageable when your care team knows you take both. Keep taking both medicines exactly as prescribed unless your prescriber tells you otherwise. Your team will typically start amitriptyline at the lowest reasonable dose and titrate slowly to the effect you need. They may check amitriptyline blood levels and adjust the dose based on results. They will watch for side effe… 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Cobicistat or Amitriptyline 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)
- Product Information: amitriptyline HCl oral tablet, amitriptyline HCl oral tablet. RemedyRepack Inc. (per DailyMed), Indiana, PA, 2010. DailyMed
- Product Information: TYBOST(R) oral tablets, cobicistat oral tablets. Gilead Sciences Inc (per FDA), Foster City, CA, 2025. DailyMed
- Product Information: SYMTUZA(R) oral tablets, darunavir, cobicistat, emtricitabine, tenofovir alafenamide oral tablets. Janssen Products, LP (per FDA), Horsham, PA, 2023. DailyMed
- Product Information: PREZCOBIX® PED oral tablets for suspension, darunavir cobicistat oral tablets for suspension. Janssen Products, LP (per FDA), Horsham, PA, 2026. DailyMed
- Product Information: PREZCOBIX® oral tablets, darunavir cobicistat oral tablets. Janssen Products, LP (per FDA), Horsham, PA, 2026. DailyMed
Keep reading about Amitriptyline
Keep reading about Cobicistat
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