Drug & supplement interaction

Gras + Efavirenz

Efavirenz brand name: Sustiva.

No Known Interaction
Medically reviewed by · Updated June 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Gras and Efavirenz in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first.

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Interaction report

Gras and Efavirenz

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Efavirenz and Gras in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

Worth understanding: our licensed dataset holds no drug-interaction record for Gras at all — not against Efavirenz, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Gras safety at a glance

Gras overall Not established We cannot confirm what "Gras" is, so its safety is unknown.
Pregnancy Avoid Because the product is unidentified, avoid it during pregnancy unless a doctor confirms it is safe.
Breastfeeding Avoid With no reliable information, avoid it while breastfeeding unless cleared by your doctor.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Efavirenz and Gras? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

What Efavirenz’s Own FDA Label Lists

This is not an interaction — none of it involves Gras. These are the most notable effects listed in the ADVERSE REACTIONS section of Efavirenz’s own FDA label, for the medication by itself. Knowing the drug’s own list makes it easier to work out the likely cause if something new turns up while you take both. One of them is worth acting on rather than waiting out — marked below.

  • Liver problems Worth acting on
  • Vivid dreams or nightmares
  • Trouble sleeping
  • Tiredness
  • Dizziness
  • A skin rash
  • Vomiting
  • Headache
  • Nausea

From the ADVERSE REACTIONS section of the FDA label for Efavirenz. Read the label on DailyMed › Gras’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Gras side to compare — that is a limit of the record, not a statement that Gras has no side effects.

Everything else you take

See Every Supplement That Interacts With Efavirenz

This page covers Gras only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Efavirenz page lists 159 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 · 117 moderate · 39 minor.

From our pharmacist’s overview on the Efavirenz page

“Efavirenz (Sustiva) is an HIV medicine, so an interaction that weakens it can cost more than a bad day; it can invite viral resistance. That makes this a list to treat with genuine care.”

Reviewed by 2 · Jul 18, 2026

Open the Efavirenz interaction page

How much people look this up

Where Gras and Efavirenz 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 Gras
Steady interest

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

29 days ago today
Medication Efavirenz
Top half

#1,196 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions. Gras is not yet covered by that licensed database, so its write-up cites publicly available medical sources directly (see the references below).
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Gras reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Gras and Efavirenz records this page draws on were last updated June 20, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Gras

What is Gras?

We could not find reliable information about a dietary supplement or herb called "Gras." The name may be a misspelling, a brand name, or a local/regional term, so we cannot confirm what it is, what it does, or whether it is safe. Please double-check the name with your pharmacist or the product label before using it.

An interaction check asks whether these two react with each other — it does not ask whether Gras is a good idea for someone in your situation. Here is what our Gras record says about it on its own.

Gras: dosing

There is no established or recommended dose for "Gras" because the product cannot be reliably identified. We will not guess an amount. If you have a labeled product, follow the manufacturer's instructions only after confirming the actual ingredient with a pharmacist or doctor.

From our Gras monograph — the full record covers uses, side effects and every documented interaction.

Read the full Gras monograph & all interactions
Medication

About Efavirenz

What Is Efavirenz Used For?

Brand name: Sustiva

Efavirenz is used to treat HIV-1 (human immunodeficiency virus type 1) infection. It is always used together with other antiretroviral medicines — never on its own.

It is approved for adults and for children who are at least 3 months old and weigh at least 3.5 kg (about 7.7 lbs). Both the capsule and tablet forms are approved for this use.

Most-Reported Side Effects for Efavirenz

From FAERS, the FDA’s public side-effect reporting system (0 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Virologic failure 960 reports
Drug resistance 742 reports
Viral mutation identified 676 reports
Pathogen resistance 641 reports
Foetal exposure during pregnancy 621 reports
See full Efavirenz drug information
Keep checking

Other Drugs & Gras

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Gras list.

See the full Gras interactions page
See every supplement checked against Efavirenz, ranked by severity
Evidence & sources

Gras References

The 3 sources that drive our Gras monograph — publicly available pages from reputable medical and government organizations. Every link was verified to work before publishing. Gras is not covered by the licensed Natural Medicines interaction database, so its page cites these public sources directly.

  1. Dietary and Herbal Supplements — NIH NCCIH Source
  2. Herbs and Supplements — MedlinePlus Source
  3. Generally Recognized as Safe (GRAS) — U.S. Food and Drug Administration Source

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Gras and Efavirenz Together: Common Questions

Is it safe to take Gras with Efavirenz?
We do not list a known interaction between Gras and Efavirenz. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Does Efavirenz interact with any supplements?
Yes. Efavirenz has documented interactions with 159 supplements in our database — Gras is not one of them. The Efavirenz interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Gras monograph Uses, safety profile, and every drug interaction in one place Efavirenz drug information The full plain-English guide to this medication Efavirenz supplement interactions Every supplement checked against Efavirenz, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 3 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Efavirenz and Gras?

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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.