Supplements and Ritonavir.
Ritonavir, sold under the brand name Norvir, is classified under "hiv protease inhibitor" in the BNF.
Ritonavir is an HIV protease inhibitor. The class blocks the viral enzyme that cleaves precursor proteins into mature infectious virus, and it is almost always used within combination antiretroviral therapy. Two features drive the supplement rules. Protease inhibitors are CYP3A4 substrates with little margin for error, and the whole point of treatment is a steady drug level that keeps the virus suppressed. Ritonavir is the telling exception: at low dose it is used deliberately as a CYP3A4 inhibitor to raise the levels of the partner drug. Supplements that induce CYP3A4 push levels the wrong way and risk treatment failure and resistance. St John's Wort is the textbook exclusion here, and garlic supplements cut unboosted saquinavir levels by about half in a controlled study (Piscitelli 2001); modern boosted regimens would blunt the size of that effect but not the direction. Supplements that inhibit CYP3A4, including curcumin, quercetin, resveratrol, schisandra and berberine, push levels up toward toxicity instead. Immune-active herbs (echinacea, andrographis, elderberry, cordyceps, astragalus) are excluded as a precaution on antiretroviral therapy regardless of CD4 count. The HIV team, not community pharmacy, signs off any supplement.
Below are the 1 documented pair we have explicitly assessed against Ritonavir in the Distil database: 1 red. The pairs cluster around 1 mechanism: CYP3A4 induction. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Last reviewed 14 June 2026. Each interaction below is assessed against PubMed-indexed evidence.
CYP3A4 induction
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
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How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
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