Lansoprazole and Nelfinavir: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Nelfinavir
Lansoprazole
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 nelfinavir plasma concentrations and risk of diminished therapeutic effect of nelfinavir
Interaction Deep Dive
The concomitant use of nelfinavir and proton pump inhibitors, which increase gastric pH, is not recommended as this may result in a reduction in nelfinavir absorption and reduced nelfinavir plasma concentrations, loss of nelfinavir efficacy, and development of resistance12. Coadministration of nelfinavir and omeprazole significantly reduced the systemic exposure of nelfinavir and its active metabolite, M8 in an open-label, two-period, single-fixed sequence study in 20 subjects 3.
Why it happens (mechanism)
Reduced absorption of nelfinavir due to an increase in gastric pH
Literature reports
2 reports — tap to read
a) Coadministration of nelfinavir and omeprazole appeared to significantly reduce the systemic exposure of nelfinavir and its active metabolite, M8. In an open-label, two-period, single-fixed sequence study, 20 subjects (ages 18 to 48 years) received nelfinavir 1250 mg every 12 hours days 1 through 3 and 1250 mg the morning of day 4 (period 1). Following a 7 day washout, subjects received omeprazole 40 mg every 24 hours and nelfinavir 1250 mg every 12 hours for 3 days and omeprazole 40 mg with nelfinavir 1250 mg the morning of day 4 (period 2). Plasma samples showed decreases of 36%, 37%, and 39% in nelfinavir Cmax, AUC, and Cmin, respectively, compared to nelfinavir alone. In addition, the M8 metabolite was measured and showed a reduction of 92% (Cmax), 89% (AUC), and 75% (Cmin) 3.
b) In a retrospective cohort study of adult HIV-positive patients who received at least 2 prescriptions for nelfinavir, an intent-to-treat (ITT)-like analysis revealed increased risk for virologic rebound in patients with concomitant proton-pump inhibitor (PPI) exposure, particularly long-term exposure, compared with those who were not exposed; however, an as-treated analysis found no significant difference in virologic rebound between the 2 groups. The primary endpoints were time to virologic undetectability (HIV viral load less than 75 copies/mL) and time to virologic rebound (HIV viral load 75 copies/mL or more after previous virologic undetectability). Patients were followed until nelfinavir discontinuation, an insurance lapse of 3 or more months, a delay of more than 30 days in nelfinavir refill, achievement of primary endpoint, or end of study. The ITT-like analysis assumed continuous use of PPI once prescribed whereas in the as-treated analysis, patients were considered to be exposed to the PPI only until 30 days after the last PPI refill was expected to run out. There was no significant difference in the time to virologic undetectability in either analysis. However, the ITT-like adjusted results showed a significantly increased risk for virologic rebound in nelfinavir-treated patients with PPI exposure compared with those with no PPI exposure (hazard ratio (HR), 1.53; 95% confidence interval (CI), 1.06 to 2.19; p=0.02). Stratifying data by length of PPI exposure revealed a 56% increased risk of virologic rebound (HR, 1.56; 95% CI, 1.08 to 2.26; p=0.02) with long-term exposure (30 days or greater) but not with short-term exposure (less than 30 days); however, this increased risk was not significant in the as-treated analysis 4.
Common questions
Can I take Lansoprazole and Nelfinavir together?
Decreased nelfinavir plasma concentrations and risk of diminished therapeutic effect of nelfinavir Always confirm with your pharmacist or prescriber before making any change.
How serious is the Lansoprazole and Nelfinavir interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Lansoprazole or Nelfinavir 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 a safer alternative to one of these medications for me?
References (4)
- Product Information: DEXILANT oral delayed-release capsules, dexlansoprazole oral delayed-release capsules. Takeda Pharmaceuticals America, Inc. (per FDA), Deerfield, IL, 2015. DailyMed
- Product Information: VIRACEPT(R) oral powder, tablets, nelfinavir mesylate oral powder, tablets. Agouron Pharmaceuticals,Inc. LaJolla, CA, 2008. DailyMed
- Fang AF, Damle BD, LaBadie RR, et al: Significant decrease in nelfinavir systemic exposure after omeprazole coadministration in healthy subjects. Pharmacotherapy 2008; 28(1):42-50. PubMed
- Saberi P, Ranatunga DK, Quesenberry CP, et al: Clinical implications of the nelfinavir-proton pump inhibitor drug interaction in patients with human immunodeficiency virus. Pharmacotherapy 2011; 31(3):253-261. PubMed
Keep reading about Nelfinavir
Keep reading about Lansoprazole
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist