Drug & supplement interaction

Basil + Guanadrel Sulfate

Guanadrel Sulfate brand name: Hylorel.

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

Basil has a moderate interaction with Guanadrel Sulfate. Theoretically, basil might increase the risk of hypotension when taken with antihypertensive drugs.

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

Basil and Guanadrel Sulfate

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Guanadrel Sulfate

Guanadrel Sulfate falls under ANTIHYPERTENSIVE DRUGS — the group Basil interacts with.

Theoretically, basil might increase the risk of hypotension when taken with antihypertensive drugs.
Animal research suggests that basil extract can reduce systolic and diastolic blood pressure.
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

Guanadrel (Hylorel) is an older blood pressure medicine that works by lowering the activity of certain nerves that tighten your blood vessels. The concern here is simple: basil may have its own mild blood pressure lowering effect, so pairing it with guanadrel could push your pressure down a little too far. That can leave you feeling dizzy, lightheaded, weak, or faint, especially when you stand up quickly.

Keep in mind this is based only on lab and animal studies, so it is more of a theoretical caution than a proven problem. The sprinkle of basil on your dinner is very unlikely to matter. Concentrated basil supplements or essential oils are the bigger question. Before starting those, check with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Umar, A., Imam, G., Yimin, W., Kerim, P., Tohti, I., Berke, B., and Moore, N. Antihypertensive effects of Ocimum basilicum L. (OBL) on blood pressure in renovascular hypertensive rats. Hypertens.Res 5-7-2010; 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

Basil Also Interacts With Other Medications

Basil has 288 moderate known drug interactions in our database — the Guanadrel Sulfate one above is one of them. If you take anything else, check it against the full list below.

Moderate 288 No known interaction 2,542 (incl. Guanadrel Sulfate)
Taking anything else?

Check Another of Your Medications Against Basil

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

From our Q&A

Questions About Basil or Guanadrel Sulfate

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Basil or Guanadrel Sulfate, 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 Guanadrel Sulfate

This page covers Basil only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Guanadrel Sulfate page lists 137 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), Tyramine (major) and Adrafinil (moderate).

By severity: 4 major · 112 moderate · 21 minor.

From our pharmacist’s overview on the Guanadrel Sulfate page

“People taking guanadrel sulfate (Hylorel) are working to hold blood pressure in a steady range, and that is precisely what most of the 137 supplements on this list disturb, so it warrants genuine vigilance. Nearly all of them push pressure one way or the other, either stacking with guanadrel until it drops too far or working against it…”

Reviewed by 2 · Jul 18, 2026

Open the Guanadrel Sulfate interaction page

One more smart check

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

We hold 396 real supplement products containing Basil, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Basil. Your product may carry other ingredients that interact with Guanadrel Sulfate too, on top of Basil — 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 Basil and Guanadrel Sulfate 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 Basil
Top half

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

29 days ago today
Medication Guanadrel Sulfate
Steady interest

#2,145 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 Basil

What is Basil?

Basil
  • Digestive upset and gas
  • Stress and anxiety
  • Antimicrobial support
  • Cold and cough symptoms
  • Headache
  • General antioxidant support

Basil is a popular cooking herb that is generally safe in the amounts used in food. While it has a long history of traditional medicinal use and contains antioxidant compounds, strong human evidence for most health claims is limited. Talk with your pharmacist or doctor before using concentrated supplements or essential oils.

Read the full Basil monograph & all interactions
Keep checking

Other Drugs & Basil

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

0Major
288Moderate
0Minor
2,541No known interaction
288 Moderate 2,541 No interaction
Moderate

288 interactions

Showing 60 of 288 moderate interactions — see all 288 on the Basil page.

No interaction 2,541 drugs checked — show the list

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

Showing the 60 most looked-up of 2,541 medications checked with no known interaction — see the full Basil list.

See the full Basil interactions page
See every supplement checked against Guanadrel Sulfate, 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
Basil monograph › Uses, safety, and every drug interaction in one place Guanadrel Sulfate supplement interactions › Every supplement checked against Guanadrel Sulfate, 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 Basil and Guanadrel Sulfate Together: Common Questions

Can you take Basil with Guanadrel Sulfate?
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.
How serious is the Basil and Guanadrel Sulfate 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 Guanadrel Sulfate and Basil?

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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.