What the FDA labels say about taking them together
Atazanavir and irinotecan
Atazanavir's FDA label of August 6, 2025 names irinotecan in its contraindications section, and irinotecan's label names atazanavir too. The atazanavir label: “Coadministration of REYATAZ with irinotecan is contraindicated. Atazanavir inhibits UGT1A1 and may interfere with the metabolism of irinotecan, resulting in increased irinotecan toxicities.”
Check it at the source: the atazanavir FDA label on DailyMed (effective August 6, 2025, Aurobindo Pharma Limited); the irinotecan FDA label on DailyMed (effective May 12, 2026, Pharmacia & Upjohn Company LLC).
What does the atazanavir label say about irinotecan?
Atazanavir label, contraindicationsDrug Class: Antineoplastics; Drugs within class that are contraindicated with atazanavir capsules: Apalutamide, encorafenib, irinotecan, ivosidenib
Atazanavir label, drug interactionsConcomitant Drug Class/Specific Drugs: Antineoplastics: irinotecan apalutamide ivosidenib encorafenib; Effect on Concentration of Atazanavir or Concomitant Drug: ↑ irinotecan ↓ atazanavir ↓ atazanavir ↑ ivosidenib ↓ atazanavir ↑ encorafenib; Clinical Comment: Coadministration of atazanavir with irinotecan is contraindicated. Atazanavir inhibits UGT1A1 and may interfere with the metabolism of irinotecan, resulting in increased irinotecan toxicities [see ]. Coadministration of atazanavir (with or without ritonavir) and apalutamide is contraindicated due to the potential for subsequent loss of virologic response and possible resistance to the class of protease inhibitors [see ]. …
Reyataz label (E.R. Squibb & Sons, L.L.C., December 5, 2024), drug interactionsConcomitant Drug Class/Specific Drugs: Antineoplastics: irinotecan; Effect on Concentration of Atazanavir or Concomitant Drug: ↑ irinotecan; Clinical Comment: Coadministration of REYATAZ with irinotecan is contraindicated. Atazanavir inhibits UGT1A1 and may interfere with the metabolism of irinotecan, resulting in increased irinotecan toxicities [see ].
Source: FDA drug label (Reyataz, NDA021567), E.R. Squibb & Sons, L.L.C., effective December 5, 2024 (SPL set 165cff62-b284-4a27-a65d-9ec8a5bfcdd8), via openFDA
Source: FDA drug label (Atazanavir Sulfate), Aurobindo Pharma Limited, effective August 6, 2025 (SPL set 7fbea274-d6b5-4faa-bbf0-05fefab42114), via openFDA; the full label on DailyMed
What does the irinotecan label say about atazanavir?
Irinotecan label, drug interactionsCoadministration of CAMPTOSAR with other inhibitors of CYP3A4 (e.g., clarithromycin, indinavir, itraconazole, lopinavir, nefazodone, nelfinavir, ritonavir, saquinavir, telaprevir, voriconazole) or UGT1A1 (e.g., atazanavir, gemfibrozil, indinavir) may increase systemic exposure to irinotecan or SN-38.
Source: FDA drug label (Onivyde, NDA207793), Ipsen Biopharmaceuticals, Inc., effective March 3, 2025 (SPL set c8b58efa-1820-48a4-b70d-62918fc4abfc), via openFDA
Source: FDA drug label (Camptosar), NDA020571 (Pfizer Inc), as published by Pharmacia & Upjohn Company LLC, effective May 12, 2026 (SPL set e518dfc6-7e93-4fee-a66c-51e1ab71c056), 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
| Atazanavir | Irinotecan | |
|---|---|---|
| Labeled for | HIV | Colorectal cancer |
| Boxed warning | No | Yes |
| Pharmacy cost (NADAC) | $2.23 per capsule 300 mg capsule | n/a |
| Shortage now | No current entry | A presentation being discontinued |
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