What the FDA labels say about taking them together
Doravirine/islatravir and lamivudine
Doravirine/islatravir's FDA label of April 20, 2026 names lamivudine in its contraindications section; the lamivudine labels PlainMeds reads (2) do not name doravirine/islatravir. The doravirine/islatravir label: “Co-administration is contraindicated with lamivudine or emtricitabine.”
Check it at the source: the doravirine/islatravir FDA label on DailyMed (effective April 20, 2026, Merck Sharp & Dohme LLC); the lamivudine FDA label on DailyMed (effective January 5, 2026, Strides Pharma Science Limited).
What does the doravirine/islatravir label say about lamivudine?
Doravirine/islatravir label, contraindicationsCONTRAINDICATIONS IDVYNSO is contraindicated when co-administered with: drugs that are strong cytochrome P450 (CYP)3A enzyme inducers as significant decreases in doravirine plasma concentrations may occur, which may decrease the effectiveness of IDVYNSO [see Warnings and Precautions (5.2), Drug Interactions (7.2), and Clinical Pharmacology (12.3) ]. lamivudine (3TC) or emtricitabine (FTC) as significant decreases in islatravir-triphosphate (ISL-TP) concentrations may occur, which may decrease the effectiveness of IDVYNSO [see Warnings and Precautions (5.2), Drug Interactions (7.2) and Clinical Pharmacology (12.3) ].
Doravirine/islatravir label, drug interactionsConcomitant Drug Class/Drug Name: Anti-virals lamivudine emtricitabine; Effect on Concentration: ↓ ISL-TP; Clinical Comment: Co-administration is contraindicated with lamivudine or emtricitabine.
Source: FDA drug label (IDVYNSO), NDA216964 (Msd), as published by Merck Sharp & Dohme LLC, effective April 20, 2026 (SPL set 11aaeb53-9848-433c-be7f-db8a5bc0b26f), via openFDA; the full label on DailyMed
What does the lamivudine label say about doravirine/islatravir?
Lamivudine's label (effective January 5, 2026) and its 1 other brand-application label do not name doravirine/islatravir in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Lamivudine), Strides Pharma Science Limited, effective January 5, 2026 (SPL set ac824c7e-9c9f-487b-ad2f-d50eaef5cbda), 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
| Doravirine/islatravir | Lamivudine | |
|---|---|---|
| Labeled for | HIV | HIV, Hepatitis B |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | n/a | $0.489 per tablet 150 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