Drug & supplement interaction

Black Hellebore + Cobicistat

Cobicistat brand name: Tybost.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Black Hellebore and Cobicistat 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. Additionally, although there is no interaction, the label for Cobicistat states a food rule worth keeping to, and the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Black Hellebore and Cobicistat

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 Cobicistat and Black Hellebore 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.

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.

Black Hellebore safety at a glance

Black Hellebore overall Avoid All parts are poisonous and can cause serious, potentially fatal harm.
Pregnancy Likely Unsafe When used orally because it can have menstrual stimulant or abortifacient effects; avoid using. Read the full pregnancy detail
Breastfeeding Likely Unsafe When used orally; avoid using. Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Cobicistat and Black Hellebore? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Cobicistat

Interactions in our licensed database are recorded against drug classes, not just single drug names. Cobicistat is filed under 2 classifications — cytochrome p450 3a4 (cyp3a4) inhibitors, oral drugs. Black Hellebore has documented interactions with 6 drug classes — the most serious being digoxin (lanoxin) (moderate), diuretic drugs (moderate) and macrolide antibiotics (moderate) — and none of Cobicistat’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Black Hellebore Does Interact With Other Medications

Black Hellebore has 133 moderate known drug interactions in our database — Cobicistat isn’t one of them. If you take anything else, check it against the full list below.

Moderate 133 No known interaction 2,697 (incl. Cobicistat)
Taking anything else?

Check Another of Your Medications Against Black Hellebore

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

What to actually watch for

No Interaction Found — But Data Suggests Black Hellebore and Cobicistat May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Diarrhea / Vomiting / Nausea Additional detail

    Black Hellebore

    “Orally, black hellebore can cause GI irritation and an irregular heartbeat (18, 19). The symptoms of poisoning from black hellebore include scratchy throat or mouth, salivation, nausea, vomiting, diarrhea, dizziness, shortness of breath, spasm, and asphyxiation (18).

    Topically, the fresh plant may cause irritation or inflammation when handled (19).”

    Black Hellebore · Natural Medicines adverse-effect record, reported in diarrhea.

    2 sources cited
    1. 18. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
    2. 19. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

    “Orally, black hellebore can cause GI irritation (19). The symptoms of poisoning from black hellebore include scratchy throat or mouth, nausea, vomiting, and diarrhea (18).”

    Black Hellebore · Natural Medicines adverse-effect record, reported in diarrhea.

    2 sources cited
    1. 19. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
    2. 18. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.

    Cobicistat

    Listed in the ADVERSE REACTIONS section of the FDA label for Cobicistat. Read the label on DailyMed ›

Reported for Black Hellebore but not commonly for Cobicistat: an irregular heartbeat, shortness of breath, sore throat and dizziness.

Effects for Cobicistat come from the ADVERSE REACTIONS section of its FDA label; effects for Black Hellebore come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 20,779 voluntary FDA FAERS reports for Cobicistat that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Black Hellebore in Pregnancy & Breastfeeding

Pregnancy Likely Unsafe

When used orally because it can have menstrual stimulant or abortifacient effects; avoid using.

Lactation Likely Unsafe

When used orally; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

How to take them

Some Cobicistat Products Have a Food Rule — Black Hellebore Should Not Break It

At least one FDA label for a product containing Cobicistat says to take it with food. If you take Black Hellebore on an empty stomach out of habit, keep them separate — and take Cobicistat with a meal where the label says to.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Cobicistat products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

2 DOSAGE AND ADMINISTRATION TYBOST must be coadministered with atazanavir or darunavir at the same time, with food, and in combination with other HIV-1 antiretroviral agents.

From the Dosage and Administration section of the FDA label we read for Cobicistat — where that label names a specific product, the instruction is that product's. Read the label on DailyMed ›

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

Everything else you take

See Every Supplement That Interacts With Cobicistat

This page covers Black Hellebore only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cobicistat page lists 30 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Adrafinil (moderate), Cannabidiol (cbd) (moderate), Cannabinol (cbn) (moderate) and Cannabis (moderate).

By severity: 1 major · 19 moderate · 10 minor.

From our pharmacist’s overview on the Cobicistat page

“Activated charcoal is the one entry to understand first if you take cobicistat (Tybost). Charcoal soaks up drugs in the gut, and since cobicistat's entire job is boosting an HIV medicine to protective levels, blunting its absorption can put the whole regimen at risk.”

Reviewed by 2 · Jul 18, 2026

Open the Cobicistat interaction page

One more smart check

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

We hold 1 real supplement products containing Black Hellebore, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Hellebore. Even though Black Hellebore itself has no known interaction with Cobicistat, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Black Hellebore and Cobicistat 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 Black Hellebore
Top half

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

29 days ago today
Medication Cobicistat
Steady interest

#1,581 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.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Black Hellebore reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Black Hellebore and Cobicistat records this page draws on were last updated July 11, 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 Black Hellebore

What is Black Hellebore?

Black Hellebore
  • Constipation (historical purgative)
  • Mental and nervous disorders (historical)
  • Worm and parasite expulsion (historical)
  • Fluid retention (historical)
  • Heart conditions (historical, dangerous)

Black Hellebore is a highly toxic plant that was used in old folk medicine but has no proven, safe modern use. Because even small amounts can cause severe poisoning and dangerous heart rhythm problems, it should not be taken as a supplement. Talk to a doctor or pharmacist before considering any product that contains it.

Helleborus niger · Ranunculaceae · Root and rhizome (historically) · Rarely sold today; historically dried root, powders, and tinctures

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

Black Hellebore: dosing

There is no safe or established dose of Black Hellebore. Because it is poisonous and the line between a historical "dose" and a toxic amount is very small, no responsible dosing guidance can be given.We do not recommend taking Black Hellebore in any form. If you come across a product that contains it, do not use it without first talking to a doctor or pharmacist.

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

Read the full Black Hellebore monograph & all interactions
Medication

About Cobicistat

What Is Cobicistat Used For?

Brand name: Tybost

Tybost (cobicistat) is not itself an HIV treatment — it works by slowing the breakdown of certain HIV medicines so they stay active in your body long enough to work. Specifically, Tybost is used to boost the HIV medicines atazanavir or darunavir (once-daily dosing) as part of a complete HIV-1 treatment regimen in adults and in children weighing at least 14 kg (about 31 lbs).

Tybost is not interchangeable with ritonavir (another booster) for all HIV medicines. It is not recommended with darunavir twice-daily, fosamprenavir, saquinavir, or tipranavir.

Most-Reported Side Effects for Cobicistat

From FAERS, the FDA’s public side-effect reporting system (20,779 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Bone density decreased 8,112 reports
Chronic kidney disease 4,754 reports
Renal injury 4,577 reports
Tooth loss 4,186 reports
Bone loss 4,107 reports
See full Cobicistat drug information
Keep checking

Other Drugs & Black Hellebore

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

0Major
133Moderate
0Minor
2,696No known interaction
133 Moderate 2,696 No interaction
Moderate

133 interactions

Showing 60 of 133 moderate interactions — see all 133 on the Black Hellebore page.

No interaction 2,696 drugs checked — show the list

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

Showing the 60 most looked-up of 2,696 medications checked with no known interaction — see the full Black Hellebore list.

See the full Black Hellebore interactions page
See every supplement checked against Cobicistat, ranked by severity
Evidence & sources

Black Hellebore References

The 5 references that drive our Black Hellebore monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Tyler VE. Herbs of Choice. Binghamton, NY: Pharmaceutical Products Press, 1994.
  2. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
  3. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.
  4. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  5. Burnham TH, ed. Drug Facts and Comparisons, Updated Monthly. Facts and Comparisons, St. Louis, MO.

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 Black Hellebore and Cobicistat Together: Common Questions

Is it safe to take Black Hellebore with Cobicistat?
We do not list a known interaction between Black Hellebore and Cobicistat. 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.
Do Black Hellebore and Cobicistat have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Should I take Black Hellebore and Cobicistat at the same time of day?
At least one FDA label for a product containing Cobicistat says to take it with food. If you take Black Hellebore on an empty stomach out of habit, keep them separate and take Cobicistat with a meal where the label says to. Food instructions belong to the product rather than the ingredient — two Cobicistat products can differ — so check the directions on your own box. This is about absorption, not an interaction.
How was the Black Hellebore and Cobicistat combination checked?
Interactions in our licensed database are recorded against drug classes. Cobicistat is filed under 2 classifications, and Black Hellebore has documented interactions with 6 drug classes — none of Cobicistat's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Black Hellebore interact with any other medications?
Yes. Black Hellebore has 133 documented drug interactions in our database — Cobicistat is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Cobicistat interact with any supplements?
Yes. Cobicistat has documented interactions with 30 supplements in our database — Black Hellebore is not one of them. The Cobicistat 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

Black Hellebore monograph Uses, safety profile, and every drug interaction in one place Cobicistat drug information The full plain-English guide to this medication Cobicistat supplement interactions Every supplement checked against Cobicistat, 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 5 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Cobicistat and Black Hellebore?

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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.