What the FDA labels say about taking them together
Efavirenz and ritonavir
Efavirenz's FDA label of March 31, 2024 names ritonavir in its drug interactions section; the ritonavir label PlainMeds reads does not name efavirenz. The efavirenz label: “Fosamprenavir (unboosted): Appropriate doses of the combinations with respect to safety and efficacy have not been established. Fosamprenavir/ritonavir: An additional 100 mg/day (300 mg total) of ritonavir is …”
Check it at the source: the efavirenz FDA label on DailyMed (effective March 31, 2024, Cipla USA Inc.); the ritonavir FDA label on DailyMed (effective July 23, 2026, AbbVie Inc.).
What does the efavirenz label say about ritonavir?
Efavirenz label, drug interactionsConcomitant Drug Class/Drug Name: Protease inhibitor: Fosamprenavir Calcium; Effect: ↓ amprenavir; Clinical Comment: Fosamprenavir (unboosted): Appropriate doses of the combinations with respect to safety and efficacy have not been established. Fosamprenavir/ritonavir: An additional 100 mg/day (300 mg total) of ritonavir is recommended when efavirenz is administered with fosamprenavir/ritonavir once daily. No change in the ritonavir dose is required when efavirenz is administered with fosamprenavir plus ritonavir twice daily.
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
What does the ritonavir label say about efavirenz?
Ritonavir's label (effective July 23, 2026) does not name efavirenz in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Norvir), AbbVie Inc., effective July 23, 2026 (SPL set 2849298e-de6e-47bb-8194-56e075b33fc3), 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
| Efavirenz | Ritonavir | |
|---|---|---|
| Labeled for | HIV | HIV |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.28 per tablet 600 mg tablet | $0.607 per tablet 100 mg tablet |
| Shortage now | No current entry | A presentation being discontinued |
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