What the FDA labels say about taking them together
Abacavir and methadone
Abacavir's FDA label of July 17, 2025 names methadone in its drug interactions section, and methadone's label names abacavir 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 abacavir FDA label on DailyMed (effective July 17, 2025, Mylan Institutional Inc.); the methadone FDA label on DailyMed (effective December 8, 2025, Epic Pharma, LLC).
What does the abacavir label say about methadone?
Abacavir label, drug interactionsDRUG INTERACTIONS Methadone: An increased methadone dose may be required in a small number of patients.
Source: FDA drug label (Ziagen, NDA020978), ViiV Healthcare Company, effective September 29, 2023 (SPL set ca73b519-015a-436d-aa3c-af53492825a1), via openFDA
Source: FDA drug label (Abacavir Sulfate), Mylan Institutional Inc., effective July 17, 2025 (SPL set 80c1702a-973c-436a-90f8-69b29674dca0), via openFDA; the full label on DailyMed
What does the methadone label say about abacavir?
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. … use of certain antiretroviral agents with 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 …
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
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
| Abacavir | Methadone | |
|---|---|---|
| Labeled for | HIV | Pain, Opioid use disorder |
| Boxed warning | Yes | Yes |
| Pharmacy cost (NADAC) | $0.546 per tablet 300 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