What the FDA labels say about taking them together
Cobicistat and efavirenz
Cobicistat's FDA label of February 10, 2026 names efavirenz in its drug interactions section; the efavirenz label PlainMeds reads does not name cobicistat. The cobicistat label: “TYBOST coadministered with darunavir: Coadministration of darunavir and TYBOST with efavirenz is not recommended because it may result in the loss of therapeutic effect and development of resistance to darunavir. …”
Check it at the source: the cobicistat FDA label on DailyMed (effective February 10, 2026, Gilead Sciences, Inc.); the efavirenz FDA label on DailyMed (effective March 31, 2024, Cipla USA Inc.).
What does the cobicistat label say about efavirenz?
Cobicistat label, drug interactionsConcomitant Drug Class/Drug Name: efavirenz; Potential Effect ↑ = Increase, ↓ = Decrease, ↔ = No change: ↓ cobicistat ↓ darunavir ↓ atazanavir; Clinical Comment: TYBOST coadministered with darunavir: Coadministration of darunavir and TYBOST with efavirenz is not recommended because it may result in the loss of therapeutic effect and development of resistance to darunavir. TYBOST coadministered with atazanavir: In treatment-naïve adult patients: Atazanavir 400 mg with TYBOST 150 mg should be coadministered once daily as a single dose with food, and efavirenz 600 mg should be administered once daily on an empty stomach, preferably at bedtime. …
Cobicistat label, warnings and precautionsMore than one antiretroviral that requires pharmacokinetic enhancement (i.e., two protease inhibitors or a protease inhibitor in combination with elvitegravir) Darunavir in combination with efavirenz, nevirapine, or etravirine Atazanavir in combination with etravirine Atazanavir in combination with efavirenz in treatment-experienced patients Darunavir 600 mg twice daily Other HIV-1 protease inhibitors including fosamprenavir, saquinavir, or tipranavir TYBOST in combination with fixed-dose combination tablets that contain cobicistat is not recommended.
Source: FDA drug label (Tybost), Gilead Sciences, Inc., effective February 10, 2026 (SPL set 3784c35c-e87f-410c-900b-8fd6313c6010), via openFDA; the full label on DailyMed
What does the efavirenz label say about cobicistat?
Efavirenz's label (effective March 31, 2024) does not name cobicistat in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Efavirenz), Cipla USA Inc., effective March 31, 2024 (SPL set 92603fa5-7a2c-4bfb-9a70-aadb4fba952c), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Cobicistat | Efavirenz | |
|---|---|---|
| Labeled for | HIV | HIV |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $1.28 per tablet 600 mg tablet |
| Shortage now | A presentation being discontinued | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once