What the FDA labels say about taking them together
Efavirenz and methadone
Efavirenz's FDA label of March 31, 2024 names methadone in its drug interactions section, and methadone's label names efavirenz too. The efavirenz label: “Monitor for signs of methadone withdrawal and increase methadone dose if required to alleviate withdrawal symptoms.”
Check it at the source: the efavirenz FDA label on DailyMed (effective March 31, 2024, Cipla USA Inc.); the methadone FDA label on DailyMed (effective December 8, 2025, Epic Pharma, LLC).
What does the efavirenz label say about methadone?
Efavirenz label, drug interactionsConcomitant Drug Class/Drug Name: Narcotic analgesic: Methadone; Effect: ↓ methadone *; Clinical Comment: Monitor for signs of methadone withdrawal and increase methadone dose if required to alleviate withdrawal 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 methadone label say about efavirenz?
Methadone label, drug interactionsClinical Impact: The concomitant use of anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. … CYP3A4 inhibitory activity, alone and in combination, such as abacavir, amprenavir, darunavir+ritonavir, efavirenz, nelfinavir, nevirapine, ritonavir, telaprevir, lopinavir+ ritonavir, saquinavir+ ritonavir, and tipranavir+ ritonavir, has resulted in increased clearance or decreased plasma levels of …
Source: FDA drug label (Diskets, NDA017058), Hikma Pharmaceuticals USA Inc., effective December 1, 2025 (SPL set e6af84de-cbfc-4a3b-bd73-6bcf77337168), via openFDA
Source: FDA drug label (Methadose, NDA017116), SpecGx LLC, effective April 27, 2026 (SPL set 808a9d0b-720b-4034-a862-5122ff514608), via openFDA
Source: FDA drug label (Methadone Hydrochloride, NDA021624), Mylan Institutional LLC, effective December 31, 2025 (SPL set 092d78eb-6423-495c-bf0d-e6532bea7138), via openFDA
Source: FDA drug label (Methadone Hydrochloride), Epic Pharma, LLC, effective December 8, 2025 (SPL set 6da7501b-b881-4bc7-891a-74214a00a3ac), 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 | Methadone | |
|---|---|---|
| Labeled for | HIV | Pain, Opioid use disorder |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $1.28 per tablet 600 mg tablet | $0.177 per tablet 10 mg tablet |
| Shortage now | No current entry | 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