What the FDA labels say about taking them together
Methadone and nelfinavir
Methadone's FDA label of December 8, 2025 names nelfinavir in its drug interactions section, and nelfinavir's label names methadone too. The methadone label: “The concomitant use of anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus.”
Check it at the source: the methadone FDA label on DailyMed (effective December 8, 2025, Epic Pharma, LLC); the nelfinavir FDA label on DailyMed (effective December 11, 2025, AGOURON).
What does the methadone label say about nelfinavir?
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. … 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 methadone. …
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), Epic Pharma, LLC, effective December 8, 2025 (SPL set 6da7501b-b881-4bc7-891a-74214a00a3ac), via openFDA; the full label on DailyMed
What does the nelfinavir label say about methadone?
Nelfinavir label, drug interactionsConcomitant Drug Class/Drug Name: Methadone; Effect on Concentration: ↓ methadone; Clinical Comment: Concentrations of methadone were decreased when coadministered with VIRACEPT. Dosage of methadone may need to be increased when coadministered with VIRACEPT.
Source: FDA drug label (VIRACEPT), AGOURON, effective December 11, 2025 (SPL set e72c2bc6-9462-4a2e-8e1d-b97592376cbd), 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
| Methadone | Nelfinavir | |
|---|---|---|
| Labeled for | Pain, Opioid use disorder | HIV |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.177 per tablet 10 mg tablet | n/a |
| 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