Drug & supplement interaction

Black Seed + Polythiazide, Reserpine

Polythiazide, Reserpine brand name: Renese R.

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

Polythiazide, Reserpine falls into 2 drug categories that Black Seed can interact with; the most serious is rated moderate. Theoretically, taking black seed with antihypertensive drugs might increase the risk of hypotension.

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

Black Seed and Polythiazide, Reserpine

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

Why Are There 2 Interactions?

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

Moderate

ANTIHYPERTENSIVE DRUGS

1 of 2

Why this applies to Polythiazide, Reserpine

Polythiazide, Reserpine falls under ANTIHYPERTENSIVE DRUGS — the group Black Seed interacts with.

Theoretically, taking black seed with antihypertensive drugs might increase the risk of hypotension.
Clinical research suggests that black seed powder and oil might reduce blood pressure by 2-3 mmHg. In animal research, black seed modestly reduces blood pressure and concomitant use of black seed and amlodipine (Norvasc) or metoprolol (Lopressor) increased the blood pressure lowering effects of these drugs.
Severity Moderate Likelihood Possible Evidence B

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

Renese R combines two blood pressure lowering medicines: polythiazide (a water pill) and reserpine (which relaxes blood vessels). Black seed has its own mild blood pressure lowering effect, usually only about 2 to 3 mmHg in studies. So the concern here is simple addition. Stack black seed on top of this combo and your pressure could dip a little lower than expected.

If it drops too far, you might feel dizzy, lightheaded, or tired, especially when standing up quickly. This is mostly theoretical and based on early research, so don't panic. Food-amount sprinkles of black seed are unlikely to matter much, but concentrated oil or capsules are worth a quick chat with your pharmacist or doctor first, particularly if your pressure already runs on the low side.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Dehkordi FR, Kamkhah AF. Antihypertensive effect of Nigella sativa seed extract in patients with mild hypertension. Fundam Clin Pharmacol 2008;22:447-52.
  2. Sahebkar A, Soranna D, Liu X, et al. A systematic review and meta-analysis of randomized controlled trials investigating the effects of supplementation with Nigella sativa (black seed) on blood pressure. J Hypertens 2016;34:2127-35. PubMed
  3. Alam MA, Bin Jardan YA, Raish M, Al-Mohizea AM, Ahad A, Al-Jenoobi FBI. Effect of Nigella sativa and fenugreek on the pharmacokinetics and pharmacodynamics of amlodipine in hypertensive rats. Curr Drug Metab. 2020;21(4):318-325. PubMed
  4. Bin Jardan YA, Ahad A, Raish M, Alam MA, Al-Mohizea AM, Al-Jenoobi FI. Effects of garden cress, fenugreek and black seed on the pharmacodynamics of metoprolol: an herb-drug interaction study in rats with hypertension. Pharm Biol 2021;59(1):1088-1097. PubMed
Moderate

DIURETIC DRUGS

2 of 2

Polythiazide, Reserpine also falls under DIURETIC DRUGS.

Theoretically, taking black seed with diuretic drugs might increase potassium loss and the risk of hypokalemia.
Black seed extract has shown diuretic effects in animals, which could theoretically increase potassium loss. This has not been shown 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

Renese R combines polythiazide, a water pill (thiazide diuretic), with reserpine for blood pressure. One thing thiazides already do is make you lose some potassium in your urine. The thought here is that black seed may add a mild diuretic push of its own, which could in theory pull your potassium down a little further.

I want to be honest about how soft this evidence is: the extra fluid-and-potassium effect of black seed has only shown up in animal and lab studies, not in people. Low potassium can cause muscle cramps, weakness, or an irregular heartbeat, so it's worth knowing. Using black seed as a kitchen spice is unlikely to matter; concentrated capsules are the bigger question mark. Before adding a black seed supplement, check with your pharmacist or doctor, especially if your potassium is ever monitored.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Zaoui, A., Cherrah, Y., Lacaille-Dubois, M. A., Settaf, A., Amarouch, H., and Hassar, M. [Diuretic and hypotensive effects of Nigella sativa in the spontaneously hypertensive rat]. Therapie 2000;55(3):379-382.

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

Black Seed Also Interacts With Other Medications

Black Seed has 911 moderate known drug interactions in our database — the Polythiazide, Reserpine one above is among them. If you take anything else, check it against the full list below.

Moderate 911 No known interaction 1,919 (incl. Polythiazide, Reserpine)
Taking anything else?

Check Another of Your Medications Against Black Seed

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

From our Q&A

Questions About Black Seed or Polythiazide, Reserpine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Black Seed or Polythiazide, Reserpine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Polythiazide, Reserpine

This page covers Black Seed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Polythiazide, Reserpine page lists 228 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Asarabacca (major) and Dolomite (major).

By severity: 10 major · 193 moderate · 25 minor.

From our pharmacist’s overview on the Polythiazide, Reserpine page

“American hellebore is the ingredient I would keep farthest from polythiazide with reserpine (Renese R), a combination pill prescribed to lower blood pressure. Its alkaloids can drop pressure and slow the heart even at small doses, and it is one of ten major-rated entries among the 228 on file here, which puts this list in the take-it-s…”

Reviewed by 2 · Jul 18, 2026

Open the Polythiazide, Reserpine interaction page

One more smart check

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

We hold 226 real supplement products containing Black Seed, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Black Seed. Your product may carry other ingredients that interact with Polythiazide, Reserpine too, on top of Black Seed — 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 Black Seed and Polythiazide, Reserpine 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 Seed
Top 25%

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

29 days ago today
Medication Polythiazide, Reserpine
Steady interest

#2,456 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 Black Seed

What is Black Seed?

Black Seed
  • Respiratory support (asthma, allergies, cough)
  • Digestive upset
  • Immune support
  • Blood sugar and cholesterol support
  • General inflammation

Black seed (Nigella sativa) is a traditional spice and remedy that has been studied for asthma, blood sugar, cholesterol, and blood pressure, with early research showing some promise but no firmly proven benefits. It is generally well tolerated in food amounts, but supplement-strength doses are less studied, so talk to your pharmacist or doctor before using it—especially if you are pregnant, breastfeeding, or take other medicines.

Read the full Black Seed monograph & all interactions
Keep checking

Other Drugs & Black Seed

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

0Major
911Moderate
0Minor
1,918No known interaction
911 Moderate 1,918 No interaction
Moderate

911 interactions

Showing 60 of 911 moderate interactions — see all 911 on the Black Seed page.

No interaction 1,918 drugs checked — show the list

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

Showing the 60 most looked-up of 1,918 medications checked with no known interaction — see the full Black Seed list.

See the full Black Seed interactions page
See every supplement checked against Polythiazide, Reserpine, 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
Black Seed monograph › Uses, safety, and every drug interaction in one place Polythiazide, Reserpine supplement interactions › Every supplement checked against Polythiazide, Reserpine, 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 Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Black Seed and Polythiazide, Reserpine Together: Common Questions

Can you take Black Seed with Polythiazide, Reserpine?
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 Black Seed and Polythiazide, Reserpine?
Polythiazide, Reserpine belongs to more than one drug category, and Black Seed 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 Black Seed and Polythiazide, Reserpine 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 Polythiazide, Reserpine and Black Seed?

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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.