What the FDA labels say about taking them together
Efavirenz and rifampin
Efavirenz's FDA label of March 31, 2024 names rifampin in its drug interactions section; the rifampin label PlainMeds reads does not name efavirenz. The efavirenz label: “… a week. Increase efavirenz to 800 mg once daily when coadministered with rifampin to patients weighing 50 kg or more.”
Check it at the source: the efavirenz FDA label on DailyMed (effective March 31, 2024, Cipla USA Inc.); the rifampin FDA label on DailyMed (effective February 11, 2026, Lupin Pharmaceuticals, Inc.).
What does the efavirenz label say about rifampin?
Efavirenz label, drug interactionsConcomitant Drug Class/Drug Name: Antimycobacterial: Rifabutin Rifampin; Effect: ↓ rifabutin * ↓ efavirenz *; Clinical Comment: Increase daily dose of rifabutin by 50%. Consider doubling the rifabutin dose in regimens where rifabutin is given 2 or 3 times a week. Increase efavirenz to 800 mg once daily when coadministered with rifampin to patients weighing 50 kg or more.
Efavirenz label, warnings and precautionsConsider potential for cross-resistance when choosing other agents. ( 5.3 ) Not recommended with ATRIPLA, which contains efavirenz, emtricitabine, and tenofovir disoproxil fumarate, unless needed for dose adjustment when coadministered with rifampin. ( 5.4 ) Serious psychiatric symptoms:
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 rifampin label say about efavirenz?
Rifampin's label (effective February 11, 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 (rifampin), Lupin Pharmaceuticals, Inc., effective February 11, 2026 (SPL set b56004f0-f23d-47f6-80c7-39884fccbccc), 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 | Rifampin | |
|---|---|---|
| Labeled for | HIV | n/a |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | $1.28 per tablet 600 mg tablet | $0.679 per capsule 300 mg capsule |
| Shortage now | No current entry | In shortage |
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