Fosamprenavir and Lopinavir and ritonavir interaction
Fosamprenavir and Lopinavir and ritonavir: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Fosamprenavir (Fosamprenavir Calcium) label · effective 2026-06-30
The list of contraindicated drugs applies to the use of fosamprenavir calcium with or without ritonavir, unless otherwise indicated.
If fosamprenavir calcium is coadministered with ritonavir, reference should be made to the full prescribing information for ritonavir for additional contraindications.
Fosamprenavir calcium is contraindicated when coadministered with the following drugs: Alpha 1-adrenoreceptor antagonist: Alfuzosin Antiarrhythmics: Flecainide (with ritonavir ), propafenone (with ritonavir ) Antimycobacterial: Rifampin Antipsychotic: Lurasidone (with ritonavir ), pimozide Ergot derivatives: Dihydroergotamine, ergonovine, ergotamine, methylergonovine…
Review ritonavir contraindications when used in combination.
…clinically significant adverse reactions, potentially leading to severe, life-threatening, or fatal events from greater exposures of concomitant medications. clinically significant adverse reactions from greater exposures of fosamprenavir calcium/ritonavir. loss of therapeutic effect of fosamprenavir calcium/ritonavir and possible development of resistance.
From the Lopinavir and ritonavir (Kaletra) label · effective 2026-07-23
…and Other Potentially Significant Drug Interactions Concomitant Drug Class: Drug Name Effect on Concentration of Lopinavir or Concomitant Drug Clinical Comments HIV-1 Antiviral Agents HIV-1 Protease Inhibitor: fosamprenavir/ritonavir ↓ amprenavir ↓ lopinavir An increased rate of adverse reactions has been observed with co-administration of these medications.
Potential for KALETRA to Affect Other Drugs Lopinavir/ritonavir is an inhibitor of CYP3A and may increase plasma concentrations of agents that are primarily metabolized by CYP3A.
Although not observed in the KALETRA/ketoconazole drug interaction study, co-administration of KALETRA and other drugs that inhibit CYP3A may increase lopinavir plasma concentrations.
Patients who exhibit these signs or symptoms should be evaluated and KALETRA and/or other antiretroviral therapy should be suspended as clinically appropriate.
Elevated transaminases with or without elevated bilirubin levels have been reported in HIV-1 mono-infected and uninfected patients as early as 7 days after the initiation of KALETRA in conjunction with other antiretroviral agents.
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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.