Drug & supplement interaction

Glycine + Clonidine

Clonidine brand name: Catapres.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Glycine and Clonidine 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 two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Glycine and Clonidine

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 Clonidine and Glycine 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.

Glycine safety at a glance

Glycine overall Use caution Generally well tolerated at typical doses, but long-term safety data are limited.
Pregnancy Use caution Not enough reliable safety data, so it is best avoided unless your doctor approves.
Breastfeeding Use caution Not enough reliable safety data, so caution is advised while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Clonidine and Glycine? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Clonidine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Clonidine is filed under 4 classifications — including alpha-adrenergic agonists, antihypertensive drugs, oral drugs. Glycine has documented interactions with 1 drug class — the most serious being clozapine (clozaril) (moderate) — and none of Clonidine’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

Glycine Does Interact With Other Medications

Glycine has 1 moderate known drug interaction in our database — Clonidine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 1 No known interaction 2,829 (incl. Clonidine)
Taking anything else?

Check Another of Your Medications Against Glycine

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

What to actually watch for

No Interaction Found — But Data Suggests Glycine and Clonidine May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Mood changes or irritability / Drowsiness / Trouble sleeping / Tiredness / Headache reported in 6.2% of FDA reports for Clonidine Additional detail

    Glycine

    “Mild sedation has occurred rarely with oral use of glycine. Symptoms resolve rapidly with discontinuation of glycine. Irritability, insomnia, fatigue, memory impairment, headache, and sensory impairment have been reported, but any association with glycine is unclear.”

    Glycine · Natural Medicines adverse-effect record, reported in cluster headache.

    3 sources cited
    1. 10252. Heresco-Levy U, Javitt DC, Ermilov M, et al. Efficacy of high-dose glycine in the treatment of enduring negative symptoms of schizophrenia. Arch Gen Psychiatry 1999;56:29-36.. PubMed
    2. 11320. Gusev EI, Skvortsova VI, Dambinova SA, et al. Neuroprotective effects of glycine for therapy of acute ischaemic stroke. Cerebrovasc Dis 2000;10:49-60. PubMed
    3. 92321. Woods SW, Walsh BC, Hawkins KA, Miller TJ, Saksa JR, D'Souza DC, Pearlson GD, Javitt DC, McGlashan TH, Krystal JH. Glycine treatment of the risk syndrome for psychosis: report of two pilot studies. Eur Neuropsychopharmacol. 2013 Aug;23(8):931-40. PubMed

    Clonidine

    Listed in the ADVERSE REACTIONS section of the FDA label for Clonidine, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

  • Dry mouth / Nausea reported in 6.1% of FDA reports for Clonidine Additional detail

    Glycine

    “Soft stools, nausea, vomiting, and upper gastrointestinal (GI) tract discomfort have occurred rarely with oral use of glycine. These symptoms resolve rapidly with discontinuation of glycine. Dry mouth has also been reported but any association to glycine is unclear.”

    Glycine · Natural Medicines adverse-effect record, reported in dry mouth.

    4 sources cited
    1. 10252. Heresco-Levy U, Javitt DC, Ermilov M, et al. Efficacy of high-dose glycine in the treatment of enduring negative symptoms of schizophrenia. Arch Gen Psychiatry 1999;56:29-36.. PubMed
    2. 11320. Gusev EI, Skvortsova VI, Dambinova SA, et al. Neuroprotective effects of glycine for therapy of acute ischaemic stroke. Cerebrovasc Dis 2000;10:49-60. PubMed
    3. 92319. Inagawa K, Kawai N, Ono K, Sukegawa E, Tsubuku S, Takahashi M. Assessment of acute adverse effects of glycine ingestion at a high dose in human volunteers. Seikatsu Eisei. 2006; 50:27-32.
    4. 92321. Woods SW, Walsh BC, Hawkins KA, Miller TJ, Saksa JR, D'Souza DC, Pearlson GD, Javitt DC, McGlashan TH, Krystal JH. Glycine treatment of the risk syndrome for psychosis: report of two pilot studies. Eur Neuropsychopharmacol. 2013 Aug;23(8):931-40. PubMed

    Clonidine

    Listed in the ADVERSE REACTIONS section of the FDA label for Clonidine, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

Reported for Glycine but not commonly for Clonidine: memory problems, diarrhea and vomiting.

Effects for Clonidine come from the ADVERSE REACTIONS section of its FDA label; effects for Glycine come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 57,112 voluntary FDA FAERS reports for Clonidine that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Overlapping uses

What Clonidine Is Prescribed For, and What Glycine Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Clonidine is a prescription medicine with approved uses on its FDA label. Glycine is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Clonidine is prescribed for: Clonidine is used to treat high blood pressure (hypertension). Several products — including Clonidine Hydrochloride tablets, Javadin oral solution, Nexiclon XR extended-release tablets, and Catapres-TTS skin patches — are approved for this use, either alone or combined with other blood pressure medicines. Extended-release formulations — including Onyda XR oral suspension and clonidine hydrochloride extended-release tablets (such as Kapvay) — are approved to treat ADHD in children and teenagers ages 6 to 17, either on their own or alongside stimulant medications. Separately, clonidine injection products (Duraclon and others) are used alongside opioid pain medicines to treat severe cancer pain that opioids alone cannot control adequately.

Glycine has been studied for:

  • Stroke studied, not established Glycine has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Glycine for stroke

    It is unclear if sublingual glycine is beneficial in patients with acute ischemic stroke.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Clonidine on your own; if you are taking Glycine for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Glycine or Clonidine

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

This page covers Glycine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Clonidine page lists 138 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 · 113 moderate · 21 minor.

From our pharmacist’s overview on the Clonidine page

“American hellebore is the ingredient I would want a clonidine (Catapres) patient to know about first. Its alkaloids lower blood pressure even in small doses and slow the heart, both things clonidine already does, so the combination can drop someone dangerously low.”

Reviewed by 2 · Jul 18, 2026

Open the Clonidine interaction page

One more smart check

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

We hold 3,022 real supplement products containing Glycine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Glycine. Even though Glycine itself has no known interaction with Clonidine, 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 Glycine and Clonidine 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 Glycine
Top 5%

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

29 days ago today
Medication Clonidine
Top half

#1,185 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 Glycine reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Glycine and Clonidine records this page draws on were last updated July 10, 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 .
Supplement

About Glycine

What is Glycine?

Glycine
  • Sleep quality and insomnia
  • Relaxation
  • Cognitive function
  • Metabolic health
  • General wellness

Glycine is a non-essential amino acid your body makes on its own and that also appears in protein-rich foods. It is most studied for improving sleep quality, where early research is promising but limited, and it appears generally well tolerated at common doses. Talk with your pharmacist or doctor before starting it, especially if you take other medicines or have a health condition.

Amino acid (made synthetically or by the body) · Powder, capsules, tablets

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

Glycine: dosing

There is no official standardized dose of glycine for any health condition. In sleep studies, a few grams taken before bedtime have been used, but the best dose for an individual is not established.The safest approach is to follow the directions on the product label and start with the lowest amount.

From our Glycine monograph — the full record covers uses, side effects and every documented interaction.

Read the full Glycine monograph & all interactions
Medication

About Clonidine

What Is Clonidine Used For?

Brand name: Catapres

Clonidine is used to treat high blood pressure (hypertension). Several products — including Clonidine Hydrochloride tablets, Javadin oral solution, Nexiclon XR extended-release tablets, and Catapres-TTS skin patches — are approved for this use, either alone or combined with other blood pressure medicines.

Extended-release formulations — including Onyda XR oral suspension and clonidine hydrochloride extended-release tablets (such as Kapvay) — are approved to treat ADHD in children and teenagers ages 6 to 17, either on their own or alongside stimulant medications. Separately, clonidine injection products (Duraclon and others) are used alongside opioid pain medicines to treat severe cancer pain that opioids alone cannot control adequately.

Most-Reported Side Effects for Clonidine

From FAERS, the FDA’s public side-effect reporting system (57,112 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Fatigue 3,519 reports
Nausea 3,475 reports
Headache 3,432 reports
Hypertension 3,275 reports
Dyspnea 2,748 reports
See full Clonidine drug information
Keep checking

Other Drugs & Glycine

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

0Major
1Moderate
0Minor
2,828No known interaction
1 Moderate 2,828 No interaction
Moderate

1 interaction

No interaction 2,828 drugs checked — show the list

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

Showing the 60 most looked-up of 2,828 medications checked with no known interaction — see the full Glycine list.

See the full Glycine interactions page
See every supplement checked against Clonidine, ranked by severity
Evidence & sources

Glycine References

The 5 references that drive our Glycine 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.

  1. Heresco-Levy U, Javitt DC, Ermilov M, et al. Efficacy of high-dose glycine in the treatment of enduring negative symptoms of schizophrenia. Arch Gen Psychiatry 1999;56:29-36.. PubMed
  2. Potkin SG, Jin Y, Bunney BG, Costa J, Gulasekaram B. Effect of clozapine and adjunctive high-dose glycine in treatment-resistant schizophrenia. Am J Psychiatry 1999;156:145-7.. PubMed
  3. Gusev EI, Skvortsova VI, Dambinova SA, et al. Neuroprotective effects of glycine for therapy of acute ischaemic stroke. Cerebrovasc Dis 2000;10:49-60. PubMed
  4. Inagawa K, Kawai N, Ono K, Sukegawa E, Tsubuku S, Takahashi M. Assessment of acute adverse effects of glycine ingestion at a high dose in human volunteers. Seikatsu Eisei. 2006; 50:27-32.
  5. Woods SW, Walsh BC, Hawkins KA, Miller TJ, Saksa JR, D'Souza DC, Pearlson GD, Javitt DC, McGlashan TH, Krystal JH. Glycine treatment of the risk syndrome for psychosis: report of two pilot studies. Eur Neuropsychopharmacol. 2013 Aug;23(8):931-40. PubMed

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 Glycine and Clonidine Together: Common Questions

Is it safe to take Glycine with Clonidine?
We do not list a known interaction between Glycine and Clonidine. 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.
Do Glycine and Clonidine have any of the same side effects?
Yes — our sources link each of them separately to 7 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Are Glycine and Clonidine used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Glycine in each. That is a conversation for your prescriber, especially if Clonidine is being adjusted to a target.
How was the Glycine and Clonidine combination checked?
Interactions in our licensed database are recorded against drug classes. Clonidine is filed under 4 classifications, and Glycine has documented interactions with 1 drug class — none of Clonidine'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 Glycine interact with any other medications?
Yes. Glycine has 1 documented drug interaction in our database — Clonidine 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 Clonidine interact with any supplements?
Yes. Clonidine has documented interactions with 138 supplements in our database — Glycine is not one of them. The Clonidine 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

Glycine monograph Uses, safety profile, and every drug interaction in one place Clonidine drug information The full plain-English guide to this medication Clonidine supplement interactions Every supplement checked against Clonidine, 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 5 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Clonidine and Glycine?

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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.