Drug & supplement interaction

Quercetin + Hydralazine, Hydrochlorothiazide, Reserpine

Hydralazine, Hydrochlorothiazide, Reserpine brand names: Ser-Ap-Es, Unipres, Uniserp.

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

Hydralazine, Hydrochlorothiazide, Reserpine falls into 3 drug categories that Quercetin can interact with; the most serious is rated moderate. Theoretically, taking quercetin with antihypertensive drugs might increase the risk of hypotension.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Quercetin and Hydralazine, Hydrochlorothiazide, Reserpine

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Quercetin interacts with whole categories of medication. Hydralazine, Hydrochlorothiazide, Reserpine falls into 3 of those categories, so it can interact with Quercetin in 3 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 3

Why this applies to Hydralazine, Hydrochlorothiazide, Reserpine

Hydralazine, Hydrochlorothiazide, Reserpine falls under ANTIHYPERTENSIVE DRUGS — the group Quercetin interacts with.

Theoretically, taking quercetin with antihypertensive drugs might increase the risk of hypotension.

Quercetin can modestly decrease blood pressure in people with mild hypertension. Theoretically, it might have additive blood pressure lowering effects when used with antihypertensive 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

This combination pill is a triple blood pressure medicine: hydralazine relaxes your blood vessels, hydrochlorothiazide is a water pill, and reserpine calms overactive nerve signals. All three lower blood pressure. Quercetin, in concentrated supplement doses, can nudge blood pressure down a little on its own. So when you stack it on top, the worry is simply additive, your pressure could dip more than expected.

What that might feel like: dizziness, lightheadedness when you stand up, fatigue, or a faster heartbeat. The good news is this is mostly theoretical and based on limited evidence, and the small amounts of quercetin in foods like onions and apples are very unlikely to matter. Before starting a high-dose supplement, check with your pharmacist or doctor so they can keep an eye on your readings.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Edwards RL, Lyon T, Litwin SE, et al. Quercetin reduces blood pressure in hypertensive subjects. J Nutr 2007;137:2405-11.
  2. Larson A, Witman MA, Guo Y, et al. Acute, quercetin-induced reductions in blood pressure in hypertensive individuals are not secondary to lower plasma angiotensin-converting enzyme activity or endothelin-1: nitric oxide. Nutr Res. 2012;32(8):557-64. PubMed
Moderate

ORGANIC ANION TRANSPORTER 3 (OAT3) SUBSTRATES

2 of 3

Hydralazine, Hydrochlorothiazide, Reserpine also falls under ORGANIC ANION TRANSPORTER 3 (OAT3) SUBSTRATES.

Theoretically, concomitant use might increase the effects and adverse effects of OAT3 substrates.

In vitro research shows that quercetin is a strong non-competitive inhibitor of OAT3, with half-maximal inhibitory concentration (IC50) values as low as 0.75 mcM. So far, this interaction 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

This combination pill pairs two blood pressure lowerers (hydralazine and reserpine) with a water pill (hydrochlorothiazide). The concern here centers on a kidney transporter called OAT3, which helps your body clear certain drugs, including the hydrochlorothiazide piece. In lab dishes, quercetin blocks this transporter fairly strongly. In theory, that could slow clearance and let drug levels climb a bit, possibly nudging up effects like extra dizziness, lightheadedness when standing, low blood pressure, or changes in your urination and electrolytes.

The honest part: this has only been seen in test tubes, never reported in real people, so it's quite theoretical. Everyday food amounts of quercetin are unlikely to matter. Before starting a concentrated supplement, just run it by your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Li C, Wang X, Bi Y, et al. Potent Inhibitors of Organic Anion Transporters 1 and 3 From Natural Compounds and Their Protective Effect on Aristolochic Acid Nephropathy. Toxicol Sci. 2020;175(2):279-291. PubMed
  2. Ni Y, Duan Z, Zhou D, et al. Identification of Structural Features for the Inhibition of OAT3-Mediated Uptake of Enalaprilat by Selected Drugs and Flavonoids. Front Pharmacol. 2020;11:802. PubMed
Moderate

ORGANIC ANION TRANSPORTER 1 (OAT1) SUBSTRATES

3 of 3

Hydralazine, Hydrochlorothiazide, Reserpine also falls under ORGANIC ANION TRANSPORTER 1 (OAT1) SUBSTRATES.

Theoretically, concomitant use might increase the effects and adverse effects of OAT1 substrates.

In vitro research shows that quercetin is a strong non-competitive inhibitor of OAT1, with half-maximal inhibitory concentration (IC50) values less than 10 mcM. So far, this interaction 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

This combination pill blends three blood pressure medicines: hydralazine (a vessel relaxer), hydrochlorothiazide (a water pill), and reserpine. The piece that connects to quercetin is how your kidneys flush certain drugs out using a 'door' called OAT1. In lab dishes, quercetin can block that door fairly strongly. The idea is that if your kidneys clear the drug a little slower, slightly more could stick around, which theoretically could nudge up effects like low blood pressure, dizziness, lightheadedness when standing, or extra fluid loss.

Here's the honest part: this has only been seen in test-tube studies, never reported in real people, so I wouldn't lose sleep over it. Food amounts of quercetin are very unlikely to matter. Before starting a high-dose supplement, just check with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ni Y, Duan Z, Zhou D, et al. Identification of Structural Features for the Inhibition of OAT3-Mediated Uptake of Enalaprilat by Selected Drugs and Flavonoids. Front Pharmacol. 2020;11:802. 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

Quercetin Also Interacts With Other Medications

Quercetin has 1,168 moderate known drug interactions in our database — the Hydralazine, Hydrochlorothiazide, Reserpine one above is among them. If you take anything else, check it against the full list below.

Moderate 1,168 No known interaction 1,662 (incl. Hydralazine, Hydrochlorothiazide, Reserpine)
Taking anything else?

Check Another of Your Medications Against Quercetin

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

Everything else you take

See Every Supplement That Interacts With Hydralazine, Hydrochlorothiazide, Reserpine

This page covers Quercetin only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Hydralazine, Hydrochlorothiazide, Reserpine page lists 231 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 · 196 moderate · 25 minor.

From our pharmacist’s overview on the Hydralazine, Hydrochlorothiazide, Reserpine page

“Ser-Ap-Es combines three blood pressure drugs, hydralazine, hydrochlorothiazide, and reserpine, so this list deserves real attention before you add a supplement. Most of the 231 ingredients on file either push blood pressure down further than intended or pile onto the diuretic and drag potassium and fluid levels with it.”

Reviewed by 2 · Jul 18, 2026

Open the Hydralazine, Hydrochlorothiazide, Reserpine interaction page

One more smart check

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

We hold 4,589 real supplement products containing Quercetin, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Quercetin. Your product may carry other ingredients that interact with Hydralazine, Hydrochlorothiazide, Reserpine too, on top of Quercetin — 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 Quercetin and Hydralazine, Hydrochlorothiazide, 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 Quercetin
Top 5%

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

29 days ago today
Medication Hydralazine, Hydrochlorothiazide, Reserpine
Steady interest

#2,099 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 Quercetin

What is Quercetin?

Quercetin
  • Seasonal allergies
  • Antioxidant support
  • Heart and blood pressure health
  • Anti-inflammatory support
  • Immune support
  • Exercise recovery

Quercetin is a plant flavonoid with antioxidant and anti-inflammatory properties found in many common foods and sold as a supplement. While early research is interesting for allergies, blood pressure, and inflammation, strong human evidence is limited for most uses. It is generally well tolerated in food amounts, but talk to your pharmacist or doctor before taking high-dose supplements.

Read the full Quercetin monograph & all interactions
Keep checking

Other Drugs & Quercetin

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

0Major
1,168Moderate
0Minor
1,661No known interaction
1,168 Moderate 1,661 No interaction
Moderate

1,168 interactions

Showing 60 of 1,168 moderate interactions — see all 1,168 on the Quercetin page.

No interaction 1,661 drugs checked — show the list

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

Showing the 60 most looked-up of 1,661 medications checked with no known interaction — see the full Quercetin list.

See the full Quercetin interactions page
See every supplement checked against Hydralazine, Hydrochlorothiazide, 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
Quercetin monograph › Uses, safety, and every drug interaction in one place Hydralazine, Hydrochlorothiazide, Reserpine supplement interactions › Every supplement checked against Hydralazine, Hydrochlorothiazide, 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 Quercetin and Hydralazine, Hydrochlorothiazide, Reserpine Together: Common Questions

Can you take Quercetin with Hydralazine, Hydrochlorothiazide, 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 3 interactions listed for Quercetin and Hydralazine, Hydrochlorothiazide, Reserpine?
Hydralazine, Hydrochlorothiazide, Reserpine belongs to more than one drug category, and Quercetin 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 Quercetin and Hydralazine, Hydrochlorothiazide, 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 Hydralazine, Hydrochlorothiazide, Reserpine and Quercetin?

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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.