Drug & supplement interaction

Shepherd's Purse + Cobicistat

Cobicistat brand name: Tybost.

No Known Interaction

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated July 2026 · Pair last verified Sep 13, 2026

The bottom line No known interaction

We found no known interaction between Shepherd's Purse 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.

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Interaction report

Shepherd's Purse 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 Shepherd's Purse 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.

Shepherd's Purse safety at a glance

Shepherd's Purse overall Use caution May be used short-term by some adults, but human safety data are limited.

Pregnancy Likely Unsafe When used orally or topically, due to possible uterine stimulation, menstrual flow stimulation, and miscarriage. Read the full pregnancy detail

Breastfeeding Avoid Not enough safety information, so avoid while breastfeeding.

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 Shepherd's Purse? 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. Shepherd's Purse has documented interactions with 2 drug classes — the most serious being cns depressants (moderate) and thyroid hormone (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

Shepherd's Purse Does Interact With Other Medications

Shepherd's Purse has 264 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 264 No known interaction 2,566 (incl. Cobicistat)

Taking anything else?

Check Another of Your Medications Against Shepherd's Purse

Covers the 2,830 medications we’ve checked against Shepherd's Purse. Pick one to open its full report.

What to actually watch for

What Shepherd's Purse Itself Has Been Linked To

This is not an interaction — nothing below involves Cobicistat. It is the side-effect record for Shepherd's Purse on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Shepherd's Purse, this list is the first place to look. 2 entries are worth acting on rather than waiting out — marked below.

A change in thyroid levels Worth acting on Additional detail
“Orally, shepherd's purse seems to be well tolerated when used in small amounts, short-term. Adverse effects traditionally thought to be associated with shepherd's purse have included sedation, hypertension, hypotension, abnormal thyroid function, abnormal menstruation (4), and palpitations (12).”

Shepherd's Purse · Natural Medicines adverse-effect record, reported in hypertension.
2 sources cited

4. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

12. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
Raised blood pressure Worth acting on Additional detail
“Orally, some adverse effects traditionally thought to be associated with shepherd's purse have included hypertension, hypotension, (4), and palpitations (12).”

Shepherd's Purse · Natural Medicines adverse-effect record, reported in hypertension.
2 sources cited

4. Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

12. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
A fast or pounding heartbeat / Low blood pressure Additional detail

Recorded for Shepherd's Purse in the same Natural Medicines adverse-effect record shown under A change in thyroid levels above.
Drowsiness Additional detail

Recorded for Shepherd's Purse in the same Natural Medicines adverse-effect record shown under A change in thyroid levels above.

Everything above comes from the Natural Medicines adverse-effect record for Shepherd's Purse — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Cobicistat’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Cobicistat column appears here.

Special populations

Shepherd's Purse in Pregnancy & Breastfeeding

Pregnancy Likely Unsafe

When used orally or topically, due to possible uterine stimulation, menstrual flow stimulation, and miscarriage.

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 — Shepherd's Purse Should Not Break It

At least one FDA label for a product containing Cobicistat says to take it with food. If you take Shepherd's Purse 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. See the Cobicistat drug page ›

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 Shepherd's Purse 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 Shepherd's Purse as Part of a Dietary Supplement Product? Check It for Interactions

We hold 73 real supplement products containing Shepherd's Purse, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Shepherd's Purse. Even though Shepherd's Purse 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 Shepherd's Purse 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 Shepherd's Purse

Steady interest

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

29 days ago today

Medication Cobicistat

Steady interest

#1,683 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 Shepherd's Purse reference on this page ↓
Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Shepherd's Purse 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 Dr. Brian Staiger, PharmD, BCPS.

Supplement

About Shepherd's Purse

What is Shepherd's Purse?

Heavy or prolonged menstrual bleeding
Minor bleeding (nosebleeds, wounds)
Mild diuretic
Digestive complaints
After-childbirth bleeding (traditional)

Shepherd's purse is a traditional herb most often used to help slow heavy menstrual bleeding and other minor bleeding, but solid human research is very limited. Because it may affect blood clotting, blood pressure, and the uterus, it should be avoided during pregnancy and used cautiously under professional guidance.

Capsella bursa-pastoris · Brassicaceae · Above-ground parts (leaves, stems, flowers, and seed pods) · Tea, liquid extract/tincture, dried herb, capsules

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

Shepherd's Purse: dosing

There is no official, standardized dose for shepherd's purse. The right amount can vary by product, form (tea, tincture, or capsule), and how concentrated it is.The safest approach is to follow the directions on the product label and not exceed them.

From our Shepherd's Purse monograph — the full record covers uses, side effects and every documented interaction.

Read the full Shepherd's Purse 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 & Shepherd's Purse

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

0Major

264Moderate

0Minor

2,565No known interaction

264 Moderate 2,565 No interaction

Moderate

264 interactions

Showing 60 of 264 moderate interactions — see all 264 on the Shepherd's Purse page.

No interaction 2,565 drugs checked — show the list

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

Showing the 60 most looked-up of 2,565 medications checked with no known interaction — see the full Shepherd's Purse list.

See the full Shepherd's Purse interactions page

See every supplement checked against Cobicistat, ranked by severity

Evidence & sources

Shepherd's Purse References

The 4 references that drive our Shepherd's Purse 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.

Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.
McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
Naafe M, Kariman N, Keshavarz Z, et al. Effect of hydroalcoholic extracts of Capsella bursa-pastoris on heavy menstrual bleeding: A randomized clinical trial. J Altern Complement Med. 2018;24(7):694-700. PubMed
Ghalandari S, Kariman N, Sheikhan Z, et al. Effect of hydroalcoholic extract of Capsella bursa pastoris on early postpartum hemorrhage: A clinical trial study. J Altern Complement Med. 2017;23(10):794-799.

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 Shepherd's Purse and Cobicistat Together: Common Questions

Is it safe to take Shepherd's Purse with Cobicistat?

We do not list a known interaction between Shepherd's Purse 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.

Should I take Shepherd's Purse 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 Shepherd's Purse 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 Shepherd's Purse and Cobicistat combination checked?

Interactions in our licensed database are recorded against drug classes. Cobicistat is filed under 2 classifications, and Shepherd's Purse has documented interactions with 2 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 Shepherd's Purse interact with any other medications?

Yes. Shepherd's Purse has 264 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 — Shepherd's Purse 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

Shepherd's Purse 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 4 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Cobicistat and Shepherd's Purse?

Our pharmacists answer your medication & supplement questions — free.

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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.