Drug & supplement interaction

Neem + Nelfinavir Mesylate

Nelfinavir Mesylate brand name: Viracept.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Nelfinavir Mesylate falls into 2 drug categories that Neem can interact with; the most serious is rated moderate. Theoretically, neem leaf extract might increase the levels and clinical effects of P-glycoprotein substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Neem and Nelfinavir Mesylate

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Neem interacts with whole categories of medication. Nelfinavir Mesylate falls into 2 of those categories, so it can interact with Neem in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

P-GLYCOPROTEIN SUBSTRATES

1 of 2

Why this applies to Nelfinavir Mesylate

Nelfinavir Mesylate falls under P-GLYCOPROTEIN SUBSTRATES — the group Neem interacts with.

Theoretically, neem leaf extract might increase the levels and clinical effects of P-glycoprotein substrates.
In vitro research shows that neem leaf methanol extract inhibits renal P-glycoprotein transport activity. So far, this reaction has not been reported in humans.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist with neem and your HIV medicine, nelfinavir (Viracept). Your body uses a kind of cellular pump called P-glycoprotein to move certain drugs around and help clear them. Nelfinavir is one of those drugs the pump handles. In lab and animal studies, neem leaf extract seems to slow this pump down. If that happened in people, more nelfinavir could stay in your system, which in theory might mean stronger effects and a higher chance of side effects like diarrhea, nausea, gas, or stomach upset.

The honest part: this is only test-tube and animal evidence, and it has never actually been reported in a real person. Still, HIV medicines are too important to gamble with, so please check with your pharmacist or doctor before adding any neem product.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Amaeze O, Marques ES, Wei W, et al. Evaluation of Nigerian Medicinal Plants Extract on Human P-glycoprotein and Cytochrome P450 Enzyme Induction: Implications for Herb-drug Interaction. Curr Drug Metab. 2021;22(14):1103-1113. PubMed
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Nelfinavir Mesylate also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, neem leaf extract might increase the levels and clinical effects of CYP3A4 substrates.
In vitro research shows that neem leaf methanol extract inhibits CYP3A4 enzymes. So far, this reaction has not been reported in humans.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the short version on combining neem with nelfinavir (Viracept). Your body relies on a liver enzyme called CYP3A4 to break down nelfinavir. In test-tube studies, neem leaf extract seems to slow that same enzyme down. If that happened in a person, nelfinavir could build up more than expected, which might mean more of its usual side effects like diarrhea, nausea, gas, or stomach upset.

The important thing to know is that this is purely theoretical right now. It's based only on lab research, and it has never actually been reported in people taking neem. Still, since keeping your HIV treatment steady matters, I'd run any neem product past your pharmacist or doctor before starting it.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Amaeze O, Eng H, Horlbogen L, Varma MVS, Slitt A. Cytochrome P450 Enzyme Inhibition and Herb-Drug Interaction Potential of Medicinal Plant Extracts Used for Management of Diabetes in Nigeria. Eur J Drug Metab Pharmacokinet. 2021;46(3):437-450. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Neem Also Interacts With Other Medications

Neem has 1,012 moderate known drug interactions in our database — the Nelfinavir Mesylate one above is among them. If you take anything else, check it against the full list below.

Moderate 1,012 No known interaction 1,818 (incl. Nelfinavir Mesylate)
Taking anything else?

Check Another of Your Medications Against Neem

Covers the 2,830 medications we’ve checked against Neem. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Nelfinavir Mesylate

This page covers Neem only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Nelfinavir Mesylate page lists 153 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), Acacia Rigidula (moderate) and Adrafinil (moderate).

By severity: 3 major · 113 moderate · 37 minor.

From our pharmacist’s overview on the Nelfinavir Mesylate page

“Nelfinavir mesylate (Viracept) treats HIV, where a steady drug level is what keeps the virus suppressed, so this is a list to read with real care before adding any supplement. Three of the 153 ingredients on file rate major, and St.”

Reviewed by 2 · Jul 18, 2026

Open the Nelfinavir Mesylate interaction page

One more smart check

Taking Neem as Part of a Dietary Supplement Product? Check It for Interactions

We hold 288 real supplement products containing Neem, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Neem. Your product may carry other ingredients that interact with Nelfinavir Mesylate too, on top of Neem — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Neem and Nelfinavir Mesylate Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Neem
Top 25%

#359 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Nelfinavir Mesylate
Top half

#1,127 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Neem

What is Neem?

Neem
  • Skin conditions
  • Dental and gum health
  • Antimicrobial and antiparasitic
  • Digestive upset
  • Blood sugar support
  • Insect repellent/pesticide

Neem is a tree from India used for centuries in traditional medicine, especially for skin, dental, and antimicrobial purposes. Some small studies are promising for oral health and skin, but high-quality human evidence is limited for most uses. Neem oil and seed extracts can be toxic if swallowed, especially in children, so use with caution and talk to your pharmacist or doctor first.

Read the full Neem monograph & all interactions
Medication

About Nelfinavir

What Is Nelfinavir Used For?

Brand name: Viracept

Viracept (nelfinavir) is used to treat HIV-1 infection. It is always taken alongside other antiretroviral (HIV-fighting) medicines — it is not used alone.

Viracept tablets are approved for adults, adolescents 13 years and older, and children aged 2 to less than 13 years.

See full Nelfinavir drug information
Keep checking

Other Drugs & Neem

Browse every other medication we’ve checked against Neem — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
1,012Moderate
0Minor
1,817No known interaction
1,012 Moderate 1,817 No interaction
Moderate

1,012 interactions

Showing 60 of 1,012 moderate interactions — see all 1,012 on the Neem page.

No interaction 1,817 drugs checked — show the list

We also checked Neem against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,817 medications checked with no known interaction — see the full Neem list.

See the full Neem interactions page
See every supplement checked against Nelfinavir Mesylate, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Neem monograph › Uses, safety, and every drug interaction in one place Nelfinavir Mesylate supplement interactions › Every supplement checked against Nelfinavir Mesylate, ranked by severity Nelfinavir drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Neem and Nelfinavir Mesylate Together: Common Questions

Can you take Neem with Nelfinavir Mesylate?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Neem and Nelfinavir Mesylate?
Nelfinavir Mesylate belongs to more than one drug category, and Neem interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Neem and Nelfinavir Mesylate interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Nelfinavir Mesylate and Neem?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.