Lopinavir and ritonavir and Warfarin interaction
Lopinavir and ritonavir and Warfarin: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Lopinavir and ritonavir (Kaletra) label · effective 2026-07-23
Initial frequent monitoring of the INR during KALETRA and warfarin co-administration is recommended.
Anticoagulants: warfarin, rivaroxaban ↑↓ warfarin ↑ rivaroxaban Concentrations of warfarin may be affected.
From the Warfarin (Warfarin Sodium) label · effective 2026-06-24
…conivaptan, cyclosporine, darunavir/ritonavir, diltiazem, erythromycin, fluconazole, fluoxetine, fluvoxamine, fosamprenavir, imatinib, indinavir, isoniazid, itraconazole, ketoconazole, lopinavir/ritonavir, nefazodone, nelfinavir, nilotinib, oral contraceptives, posaconazole, ranitidine, ranolazine, ritonavir, saquinavir, telithromycin, tipranavir, voriconazole, zileuton…
Concomitant use of drugs that increase bleeding risk, antibiotics, antifungals, botanical (herbal) products, and inhibitors and inducers of CYP2C9, 1A2, or 3A4.
Inducers of CYP2C9, 1A2, and/or 3A4 have the potential to decrease the effect (decrease INR) of warfarin by decreasing the exposure of warfarin.
Examples of inhibitors and inducers of CYP2C9, 1A2, and 3A4 are below in Table 2 ; however, this list should not be considered all-inclusive.
Closely monitor INR if a concomitant drug is a CYP2C9, 1A2, and/or 3A4 inhibitor or inducer.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.