The short answer
High-dose niacin deserves review before oral ketoconazole because some niacin formulations can injure the liver. Do not add it on your own; this is a liver-risk precaution rather than a proven absorption interaction or timing solution.
What this answer covers
High-dose nicotinic acid supplements with oral ketoconazole. Sustained-release, immediate-release, other B3 forms and ordinary nutritional amounts differ.
- Supplement or preparation
- Niacin
- Medication ingredient
- ketoconazole
Check the exact medicine and regimen
This review applies to oral ketoconazole tablets, whose use is limited because of serious systemic risks. It does not assign the same interactions to ketoconazole shampoo or skin cream. Keep the prescribed indication, other medicines and liver-monitoring plan in view.
Why the formulation and dose matter
A randomized trial of escalating pharmacologic nicotinic-acid doses found liver toxicity with the tested sustained-release preparation, while the immediate-release arm did not show that outcome. This does not assign the same risk to ordinary food intake, nutritional-dose vitamins or every B3 form.
Not all studies had the same outcome
A shorter trial of another extended-release preparation reported generally good tolerance with small mean liver-enzyme increases. It did not include ketoconazole. Differences in dose, release formulation and duration limit any attempt to predict a universal combined risk.
Coordinate monitoring and supplements
Oral ketoconazole can cause serious liver injury and its label advises avoiding other potentially hepatotoxic agents when possible. Show the exact niacin product to the prescriber and follow the liver-monitoring plan. Moving doses a few hours apart is not established to prevent liver injury.
Evidence and practical considerations
Side effects & toxicity
The oral ketoconazole warning against other potentially hepatotoxic agents supports a conditional high-dose nicotinic-acid precaution.
- Exact scope
- High-dose nicotinic acid supplements with oral ketoconazole. Sustained-release, immediate-release, other B3 forms and ordinary nutritional amounts differ. with RxNorm 6135 IN ketoconazole. Exact oral 200 mg base tablets; topical creams, shampoos and other local routes are not comparable systemic exposure.
- Medication form and route
- Oral
What remains uncertain
- No exact combination toxicity trial. Conditional bridge from high-dose formulation-specific niacin hepatotoxicity to exact oral ketoconazole warning; no blanket nutritional-niacin ban or validated spacing.
Factors that may matter: Exact oral regimen and formulation; Booster or fixed-combination context; Mineral preparation and dosing order; Food requirements.
Read the supporting source summaries
Source 1: Current original prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed the specified oral regimen.
Reduced acidity impairs absorption; acid-neutralizing drugs at least one hour before or two hours after. Serious liver toxicity warning and contraindication with lovastatin/simvastatin.
How this applies: RxNorm 6135 IN ketoconazole. Exact oral 200 mg base tablets; topical creams, shampoos and other local routes are not comparable systemic exposure.
No automatic topical route transfer, fruit-extract interaction or every-mineral binding effect. Constituent bridges and liver-risk precaution distinct from exact-pair clinical event data.
Source 2: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 46 adults with high LDL cholesterol.
Hepatotoxicity occurred with the tested sustained-release regimen; none in immediate-release arm.
How this applies: Exact reported regimen, preparation and endpoints only; other drugs or forms remain indirect.
Abstract-only pharmacologic-dose formulations; not ketoconazole combination or ordinary dietary niacin/nicotinamide; no universal low-dose toxicity claim.
Source 3: Original clinical research
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 120 adults with mild-to-moderate dyslipidemia, three groups.
Generally good tolerance with small mean transaminase increases; inositol hexanicotinate showed no measurable bioavailability or lipid benefit.
How this applies: Exact reported regimen, preparation and endpoints only; other drugs or forms remain indirect.
Abstract-only different formulation/duration and no ketoconazole. Retains variability; not proof that all high-dose niacin combinations are safe.
Source 4: Medication terminology
rxnav.nlm.nih.gov · Source check Sep 10, 2026
Population: Terminology.
ketoconazole is IN.
How this applies: Exact ingredient.
Not clinical evidence.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Research summary published | |
| Article prepared | |
| Sources checked and article drafted. |
Article revision: 65816bd00e1169e2
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.