Drug & supplement interaction

N-acetyl Cysteine (nac) + Cyclothiazide

Cyclothiazide brand names: Fluidil, Anhydron.

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

N-acetyl Cysteine (nac) has a moderate interaction with Cyclothiazide. Theoretically, N-acetyl cysteine 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

N-acetyl Cysteine (nac) and Cyclothiazide

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

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Cyclothiazide

Cyclothiazide falls under ANTIHYPERTENSIVE DRUGS — the group N-acetyl Cysteine (nac) interacts with.

Theoretically, N-acetyl cysteine might increase the risk of hypotension when taken with antihypertensive drugs.
Animal research suggests that N-acetyl cysteine potentiates the hypotensive effects of the angiotensin-converting enzyme inhibitors (ACEIs) captopril and enalaprilat. Theoretically, combining N-acetyl cysteine with other antihypertensive drugs might increase the risk of hypotension.
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

Cyclothiazide is a thiazide water pill that lowers blood pressure by helping your body get rid of extra salt and fluid. The concern here is simple: NAC may add to that blood-pressure-lowering effect, so the two together could push your pressure down a little more than expected.

If that happens, you might feel lightheaded, dizzy, or wobbly when you stand up. I want to be honest about the strength of this, though. It comes from animal studies (and mostly with ACE inhibitors, not thiazides), so it is theoretical and far from certain. Most people won't notice anything. Still, if you take both, it's worth checking your blood pressure now and then and mentioning it to your pharmacist or doctor, especially if you feel faint.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ruiz FJ, Salom MG, Inglés AC, et al. N-acetyl-L-cysteine potentiates depressor response to captopril and enalaprilat in SHRs. Am J Physiol. 1994;267(3 Pt 2):R767-72. 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

N-acetyl Cysteine (nac) Also Interacts With Other Medications

N-acetyl Cysteine (nac) has 1 major, 292 moderate known drug interactions in our database — the Cyclothiazide one above is one of them. If you take anything else, check it against the full list below.

Major 1 Moderate 292 No known interaction 2,537 (incl. Cyclothiazide)
Taking anything else?

Check Another of Your Medications Against N-acetyl Cysteine (nac)

Covers the 2,830 medications we’ve checked against N-acetyl Cysteine (nac). Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Cyclothiazide

This page covers N-acetyl Cysteine (nac) only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cyclothiazide page lists 210 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 · 175 moderate · 25 minor.

From our pharmacist’s overview on the Cyclothiazide page

“Cyclothiazide (Fluidil, Anhydron) is a thiazide diuretic for high blood pressure and fluid retention, and its 210 supplement interactions warrant real vigilance, especially the ten rated major. Most entries pull in one of two directions.”

Reviewed by 2 · Jul 18, 2026

Open the Cyclothiazide interaction page

One more smart check

Taking N-acetyl Cysteine (nac) as Part of a Dietary Supplement Product? Check It for Interactions

We hold 3,554 real supplement products containing N-acetyl Cysteine (nac), each one broken down to its full ingredient list — and combination products often carry several ingredients besides N-acetyl Cysteine (nac). Your product may carry other ingredients that interact with Cyclothiazide too, on top of N-acetyl Cysteine (nac) — 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 N-acetyl Cysteine (nac) and Cyclothiazide 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 N-acetyl Cysteine (nac)
Top 5%

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

29 days ago today
Medication Cyclothiazide
Top half

#1,135 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 N-acetyl Cysteine (nac)

What is N-acetyl Cysteine (nac)?

N-acetyl Cysteine (nac)
  • Thinning mucus in lung conditions
  • Acetaminophen (Tylenol) overdose treatment
  • Antioxidant and glutathione support
  • Liver support
  • Respiratory health

N-acetyl cysteine (NAC) is a supplement form of the amino acid cysteine and a building block for the antioxidant glutathione. It has well-established prescription uses for acetaminophen overdose and thinning mucus, but evidence for many over-the-counter uses is still limited. It is generally well tolerated, but you should check with a pharmacist or doctor before starting it.

Read the full N-acetyl Cysteine (nac) monograph & all interactions
Keep checking

Other Drugs & N-acetyl Cysteine (nac)

Browse every other medication we’ve checked against N-acetyl Cysteine (nac) — both the ones with a known interaction and the ones without. Select any drug for the full detail.

1Major
292Moderate
0Minor
2,536No known interaction
1 Major 292 Moderate 2,536 No interaction
Major

1 interaction

Moderate

292 interactions

Showing 60 of 292 moderate interactions — see all 292 on the N-acetyl Cysteine (nac) page.

No interaction 2,536 drugs checked — show the list

We also checked N-acetyl Cysteine (nac) against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,536 medications checked with no known interaction — see the full N-acetyl Cysteine (nac) list.

See the full N-acetyl Cysteine (nac) interactions page
See every supplement checked against Cyclothiazide, 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
N-acetyl Cysteine (nac) monograph › Uses, safety, and every drug interaction in one place Cyclothiazide supplement interactions › Every supplement checked against Cyclothiazide, 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 N-acetyl Cysteine (nac) and Cyclothiazide Together: Common Questions

Can you take N-acetyl Cysteine (nac) with Cyclothiazide?
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 N-acetyl Cysteine (nac) and Cyclothiazide 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 Cyclothiazide and N-acetyl Cysteine (nac)?

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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.