Orlistat and Cobicistat: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 9, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Cobicistat
Orlistat
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
Reduced efficacy of antiretrovirals, loss of virological control
Interaction Deep Dive
Concomitant use of orlistat with antiretroviral drugs has resulted in loss of virological control. The exact mechanism for this is unclear, but may include a drug-drug interaction that inhibits systemic absorption of the antiretroviral drug. Monitor HIV RNA levels frequently in patients who take orlistat while being treated for HIV infection. If there is a confirmed increase in HIV viral load, discontinue orlistat1.
Why it happens (mechanism)
Inhibition of systemic absorption of the antiretroviral drug by orlistat
Common questions
Can I take Orlistat and Cobicistat together?
Reduced efficacy of antiretrovirals, loss of virological control Always confirm with your pharmacist or prescriber before making any change.
How serious is the Orlistat and Cobicistat 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 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 Orlistat or Cobicistat 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: XENICAL oral capsules, orlistat oral capsules. H2-Pharma, LLC (per Dailymed), Montgomery, AL, 2023. DailyMed
Keep reading about Cobicistat
Keep reading about Orlistat
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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