Drug & supplement interaction

Casein Peptides + Guanfacine

Guanfacine brand name: Tenex.

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

Casein Peptides has a moderate interaction with Guanfacine. Theoretically, combining these casein peptides with antihypertensive drugs might increase the risk of hypotension.

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

Casein Peptides and Guanfacine

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

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Guanfacine

Guanfacine falls under ANTIHYPERTENSIVE DRUGS — the group Casein Peptides interacts with.

Theoretically, combining these casein peptides with antihypertensive drugs might increase the risk of hypotension.
Clinical research shows that some casein peptides, including the lactotripeptides isoleucine-proline-proline (IPP) and valine-proline-proline (VPP), can modestly reduce blood pressure in patients with hypertension.
Severity Moderate Likelihood Probable Evidence B

Interaction 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..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the simple version: guanfacine already works to lower your blood pressure by calming the nervous system signals that keep your vessels tight. Casein peptides may nudge blood pressure down a little too, possibly by gently blocking the ACE enzyme. Stack the two together and the lowering effects can add up.

If your pressure drops too far, you might notice dizziness, lightheadedness, drowsiness, or feeling faint when you stand up, which are already common with guanfacine. That said, the proof here is modest, and the effect from these peptides is usually small. This isn't a reason to panic, but please check with your pharmacist or doctor before starting them so they can keep an eye on your readings.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Cicero AFG, Aubin F, Azais-Braesco V, Borghi C. Do the lactotripeptides isoleucine-proline-proline and valine-proline-proline reduce systolic blood pressure in European subjects? A meta-analysis of randomized controlled trials. Am J Hypertens. 2013;26(3): PubMed
  2. Fekete AA, Givens DA, Lovegrove JA. Casein-derived lactotripeptides reduce systolic and diastolic blood pressure in a meta-analysis of randomised clinical trials. Nutrients. 2015;7(1):659-81. PubMed
  3. Qin LQ, Xu JY, Dong JY, Zhao Y, van Bladeren P, Zhang W. Lactotripeptides intake and blood pressure management: a meta-analysis of randomised controlled clinical trials. Nutr Metab Cardiovasc Dis. 2013;23(5):395-402. PubMed
  4. Turpeinen AM, Järvenpää S, Kautiainen H, Korpela R, Vapaatalo H. Antihypertensive effects of bioactive tripeptides-a random effects meta-analysis. Ann Med. 2013;45(1):51-6. 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

Casein Peptides Also Interacts With Other Medications

Casein Peptides has 171 moderate known drug interactions in our database — the Guanfacine one above is one of them. If you take anything else, check it against the full list below.

Moderate 171 No known interaction 2,659 (incl. Guanfacine)
Taking anything else?

Check Another of Your Medications Against Casein Peptides

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

From our Q&A

Questions About Casein Peptides or Guanfacine

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

This page covers Casein Peptides only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Guanfacine page lists 136 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 · 111 moderate · 21 minor.

Open the Guanfacine interaction page

One more smart check

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

We hold 82 real supplement products containing Casein Peptides, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Casein Peptides. Your product may carry other ingredients that interact with Guanfacine too, on top of Casein Peptides — 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 Casein Peptides and Guanfacine 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 Casein Peptides
Steady interest

#1,109 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Guanfacine
Top half

#846 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 Casein Peptides

What is Casein Peptides?

  • High blood pressure
  • Stress and relaxation
  • Sleep support
  • General wellness/protein supplement

Casein peptides are small protein fragments made from milk casein, often studied for mild blood pressure support and relaxation. The evidence is limited and mostly modest, so they should not replace proven treatments. People with milk allergy should avoid them, and anyone with a health condition should check with a pharmacist or doctor first.

Read the full Casein Peptides monograph & all interactions
Medication

About Guanfacine

What Is Guanfacine Used For?

Brand name: Tenex

Guanfacine immediate-release tablets (Guanfacine, Guanfacine Hydrochloride) are used to manage high blood pressure (hypertension). They can be used alone or together with other blood pressure medicines, especially thiazide-type diuretics (water pills).

Guanfacine extended-release tablets — sold as Guanfacine ER, Guanfacine extended-release, and Intuniv — are approved for the treatment of ADHD in children and adolescents ages 6 to 17. They can be used on their own (monotherapy) or alongside stimulant ADHD medications as add-on therapy.

See full Guanfacine drug information
Keep checking

Other Drugs & Casein Peptides

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

0Major
171Moderate
0Minor
2,658No known interaction
171 Moderate 2,658 No interaction
Moderate

171 interactions

Showing 60 of 171 moderate interactions — see all 171 on the Casein Peptides page.

No interaction 2,658 drugs checked — show the list

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

Showing the 60 most looked-up of 2,658 medications checked with no known interaction — see the full Casein Peptides list.

See the full Casein Peptides interactions page
See every supplement checked against Guanfacine, 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
Casein Peptides monograph › Uses, safety, and every drug interaction in one place Guanfacine supplement interactions › Every supplement checked against Guanfacine, ranked by severity Guanfacine drug information › The full plain-English guide to this medication 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 Casein Peptides and Guanfacine Together: Common Questions

Can you take Casein Peptides with Guanfacine?
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 Casein Peptides and Guanfacine 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 Guanfacine and Casein Peptides?

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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.