Ascorbic Acid (Vitamin C) and Indinavir: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Indinavir
No brand names on recordAscorbic Acid (Vitamin C)
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Decreased indinavir plasma concentrations
Interaction Deep Dive
In healthy subjects, co-administration of indinavir with high-dose ascorbic acid (vitamin C) significantly reduced the serum concentration of indinavir1.
Why it happens (mechanism)
Induction of cytochrome P450 3A4-mediated indinavir metabolism
Literature reports
1 report — tap to read
a) Co-administration of indinavir with high-dose ascorbic acid (vitamin C) significantly reduced the serum concentration of indinavir. In a crossover, 2-phase study, healthy subjects (n=7) received 4 doses of indinavir 800 milligrams (mg) every 8 hours. After the 4th dose, baseline serum analysis of indinavir pharmacokinetics was completed over a 5-hour period, followed by a non-quantified wash-out phase. Thereafter, the 4-dose indinavir regimen was repeated in conjunction with concomitant administration of ascorbic acid 1 gram daily given for 1 week (concluding on the day of the 4th dose of indinavir). Dietary intake was controlled for all subjects throughout the study. The concomitant use of ascorbic acid significantly reduced by 20% the maximum serum concentration of indinavir (p=0.04) and reduced by 14% the indinavir steady-state area under the concentration-time curve (p less than 0.05). Although not statistically significant, the indinavir minimum serum (trough) concentrations were lower in the presence of ascorbic acid (265 versus 181 nanograms/milliliter, p=0.09) 1.
Common questions
Can I take Ascorbic Acid (Vitamin C) and Indinavir together?
Decreased indinavir plasma concentrations Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ascorbic Acid (Vitamin C) and Indinavir interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Ascorbic Acid (Vitamin C) or Indinavir need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (1)
- Slain D, Amsden JR, Khakoo RA et al: Effect of high-dose vitamin C (Vit C) on the steady-state pharmacokinetics (PK) of the protease inhibitor (PI) indinavir (IDV) in healthy volunteers (abstract A-1610). Presented at the 43rd Interscience Conference On Antimicrobial Agents and Chemotherapy; Chicago, IL, USA, September 14-17, 2003.
Keep reading about Indinavir
Keep reading about Ascorbic Acid (Vitamin C)
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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