Drug & supplement interaction

Blue-green Algae + Macitentan

Macitentan brand name: Opsumit.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Oct 4, 2026
The bottom line No known interaction

We found no known interaction between Blue-green Algae and Macitentan 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

Blue-green Algae and Macitentan

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 Macitentan and Blue-green Algae 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.

Blue-green Algae safety at a glance

Blue-green Algae overall Use caution Quality varies and some products can be contaminated with toxins or heavy metals.
Pregnancy Avoid Not enough safety data and contamination risk; best to avoid.
Breastfeeding Avoid Safety is unknown and contamination is a concern; best to avoid.

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

Still wondering about combining Macitentan and Blue-green Algae? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Macitentan

Interactions in our licensed database are recorded against drug classes, not just single drug names. Macitentan is filed under 4 classifications — including antihypertensive drugs, hepatotoxic drugs, cytochrome p450 3a4 (cyp3a4) substrates. Blue-green Algae has documented interactions with 3 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate), antidiabetes drugs (moderate) and immunosuppressants (moderate) — and none of Macitentan’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

Blue-green Algae Does Interact With Other Medications

Blue-green Algae has 327 moderate known drug interactions in our database — Macitentan isn’t one of them. If you take anything else, check it against the full list below.

Moderate 327 No known interaction 2,503 (incl. Macitentan)
Taking anything else?

Check Another of Your Medications Against Blue-green Algae

Covers the 2,830 medications we’ve checked against Blue-green Algae. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Blue-green Algae and Macitentan 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. 2 of them are worth acting on rather than waiting out — marked below.

  • A severe allergic reaction / An allergic reaction Worth acting on Additional detail

    Blue-green Algae

    “Orally, urticarial rashes and pruritus have occurred as part of generalized allergic reactions to blue-green algae.

    In one case report, a 14-year-old male experienced anaphylaxis with urticaria, lip edema, and asthma 6 hours after taking five tablets of spirulina blue-green algae (A. platensis, strength unknown). He had a positive skin prick test.”

    Blue-green Algae · Natural Medicines adverse-effect record, reported in allergic rhinitis (hay fever).

    3 sources cited
    1. 91706. Le TM, Knulst AC, Röckmann H. Anaphylaxis to Spirulina confirmed by skin prick test with ingredients of Spirulina tablets. Food Chem Toxicol 2014;74:309-10. PubMed
    2. 91711. Rzymski P, Niedzielski P, Kaczmarek N, Jurczak T, Klimaszyk P. The multidisciplinary approach to safety and toxicity assessment of microalgae-based food supplements following clinical cases of poisoning. Harmful Algae 2015;46:34-42. DOI
    3. 91712. Petrus M, Culerrier R, Campistron M, et al. First case report of anaphylaxis to spirulin: identification of phycocyanin as responsible allergen. Allergy 2010;65(7):924-5. PubMed

    Macitentan

    Listed in the ADVERSE REACTIONS section of the FDA label for Macitentan. Read the label on DailyMed ›

  • Headache reported in 12.1% of FDA reports for Macitentan Additional detail

    Blue-green Algae

    “Orally, spirulina blue-green algae seem to be well tolerated.

    Most Common Adverse Effects:

    Orally: Abdominal cramps, bloating, diarrhea, dizziness, fatigue, flatulence, headache, nausea, and vomiting.”

    Blue-green Algae · Natural Medicines adverse-effect record, reported in cluster headache.

    Macitentan

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

  • Itching / Swelling / A skin rash Additional detail

    Blue-green Algae

    Recorded for Blue-green Algae in the same Natural Medicines adverse-effect record shown under A severe allergic reaction / An allergic reaction above.

    Macitentan

    Listed in the ADVERSE REACTIONS section of the FDA label for Macitentan. Read the label on DailyMed ›

Reported for Blue-green Algae but not commonly for Macitentan: stomach pain, muscle weakness, severe muscle breakdown and stomach upset.

Effects for Macitentan come from the ADVERSE REACTIONS section of its FDA label; effects for Blue-green Algae come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 68,860 voluntary FDA FAERS reports for Macitentan 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 Macitentan Is Prescribed For, and What Blue-green Algae Has Been Studied For

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

Macitentan is prescribed for: Macitentan tablets — sold under the brand name Opsumit — are used to treat pulmonary arterial hypertension (PAH, WHO Group I), a type of high blood pressure in the arteries of the lungs. The goal is to slow the disease from getting worse and to lower the chance of being hospitalized because of PAH. In the key clinical study, macitentan was used in adults with mainly moderate-to-severe PAH symptoms. Patients had PAH caused by unknown or inherited causes, connective tissue disorders, or congenital heart disease with repaired shunts.

Blue-green Algae has been studied for:

  • Hypertension Natural Medicines rates the evidence for Blue-green Algae: Possibly Effective Read what the research shows

    Blue-green Algae for hypertension

    Oral blue-green algae seem to modestly reduce blood pressure in patients with hypertension.

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 Macitentan on your own; if you are taking Blue-green Algae for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

Everything else you take

See Every Supplement That Interacts With Macitentan

This page covers Blue-green Algae only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Macitentan page lists 253 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), Beer (major) and Grapefruit (major).

By severity: 9 major · 205 moderate · 39 minor.

From our pharmacist’s overview on the Macitentan page

“If you take macitentan (Opsumit) for pulmonary arterial hypertension, study this page rather than skim it. It lists 253 supplement and herbal ingredients, nine rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Macitentan interaction page

One more smart check

Taking Blue-green Algae as Part of a Dietary Supplement Product? Check It for Interactions

We hold 3,180 real supplement products containing Blue-green Algae, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Blue-green Algae. Even though Blue-green Algae itself has no known interaction with Macitentan, 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 Blue-green Algae and Macitentan 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 Blue-green Algae
Top 10%

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

29 days ago today
Medication Macitentan
Top 25%

#598 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 Blue-green Algae reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified October 4, 2026. The Blue-green Algae and Macitentan 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 Blue-green Algae

What is Blue-green Algae?

Blue-green Algae
  • General nutrition and energy
  • Antioxidant support
  • Cholesterol and metabolic health
  • Immune support
  • Weight management

Blue-green algae are nutrient-rich aquatic microorganisms (such as spirulina and Klamath Lake algae) taken as a supplement for energy, nutrition, and general wellness. Evidence for most health claims is limited, and some products can be contaminated with toxins or heavy metals, so quality testing matters. Talk to your pharmacist or doctor before using, especially during pregnancy or breastfeeding.

Whole dried microorganism (algae biomass) · Tablets, capsules, powder, flakes, and liquid extracts

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

Blue-green Algae: dosing

There is no official, standardized dose for blue-green algae, and the amount varies a lot from product to product. Different species and forms (tablet, powder, or liquid) also differ in strength.The safest approach is to follow the directions on the product label and not exceed them.

From our Blue-green Algae monograph — the full record covers uses, side effects and every documented interaction.

Read the full Blue-green Algae monograph & all interactions
Medication

About Macitentan

What Is Macitentan Used For?

Brand name: Opsumit

Macitentan tablets — sold under the brand name Opsumit — are used to treat pulmonary arterial hypertension (PAH, WHO Group I), a type of high blood pressure in the arteries of the lungs. The goal is to slow the disease from getting worse and to lower the chance of being hospitalized because of PAH.

In the key clinical study, macitentan was used in adults with mainly moderate-to-severe PAH symptoms. Patients had PAH caused by unknown or inherited causes, connective tissue disorders, or congenital heart disease with repaired shunts.

Most-Reported Side Effects for Macitentan

From FAERS, the FDA’s public side-effect reporting system (68,860 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Dyspnea 11,958 reports
Headache 8,323 reports
Diarrhea 6,584 reports
Nausea 5,972 reports
Fatigue 5,041 reports
See full Macitentan drug information
Keep checking

Other Drugs & Blue-green Algae

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

0Major
327Moderate
0Minor
2,502No known interaction
327 Moderate 2,502 No interaction
Moderate

327 interactions

Showing 60 of 327 moderate interactions — see all 327 on the Blue-green Algae page.

No interaction 2,502 drugs checked — show the list

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

Showing the 60 most looked-up of 2,502 medications checked with no known interaction — see the full Blue-green Algae list.

See the full Blue-green Algae interactions page
See every supplement checked against Macitentan, ranked by severity
Evidence & sources

Blue-green Algae References

The 22 references that drive our Blue-green Algae 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. Jensen GS, Ginsberg DJ, Huerta P, et al. Consumption of Aphanizomenon flos-aquae has rapid effects on the circulation and function of immune cells in humans. A novel approach to nutritional mobilization of the immune system. JANA 2000;2:50-6.
  2. Iwasa M, Yamamoto M, Tanaka Y, et al. Spirulina-associated hepatotoxicity. Am J Gastroenterol 2002;97:3212-13. PubMed
  3. Hayashi O, Katoh T, Okuwaki Y. Enhancement of antibody production in mice by dietary Spirulina platensis. J Nutr Sci Vitaminol (Tokyo) 1994;40:431-41.. PubMed
  4. Vitale S, Miller NR, Mejico LJ, et al. A randomized, placebo-controlled, crossover clinical trial of super blue-green algae in patients with essential blepharospasm or Meige syndrome. Am J Ophthalmol 2004;138:18-32. PubMed
  5. Mani UV, Desai S, Iyer U. Studies on the long-term effect of spirulina supplementation on serum lipid profile and glycated proteins in NIDDM patients. J Nutraceut 2000;2(3):25-32. DOI
  6. Chiu HF, Yang SP, Kuo YL, et al. Mechanisms involved in the antiplatelet effect of C-phycocyanin. Br J Nutr 2006;95:435-40. PubMed
  7. Hsiao G, Chou PH, Shen MY, et al. C-phycocyanin, a very potent and novel platelet aggregation inhibitor from Spirulina platensis. J Agric Food Chem 2005;53:7734-40.
  8. Katz M, Levine AA, Kol-Degani H, Kav-Venaki L. A compound herbal preparation (CHP) in the treatment of children with ADHD: a randomized controlled trial. J Atten Disord 2010;14:281-91. PubMed
  9. Madhyastha, H. K., Radha, K. S., Sugiki, M., Omura, S., and Maruyama, M. Purification of c-phycocyanin from Spirulina fusiformis and its effect on the induction of urokinase-type plasminogen activator from calf pulmonary endothelial cells. Phytomedicine PubMed
  10. Mazokopakis, E. E., Karefilakis, C. M., Tsartsalis, A. N., Milkas, A. N., and Ganotakis, E. S. Acute rhabdomyolysis caused by Spirulina (Arthrospira platensis). Phytomedicine. 2008;15(6-7):525-527. PubMed
  11. Halidou, Doudou M., Degbey, H., Daouda, H., Leveque, A., Donnen, P., Hennart, P., and Dramaix-Wilmet, M. [The effect of spiruline during nutritional rehabilitation: systematic review]. Rev.Epidemiol.Sante Publique 2008;56(6):425-431.
  12. Konno, T., Umeda, Y., Umeda, M., Kawachi, I., Oyake, M., and Fujita, N. [A case of inflammatory myopathy with widely skin rash following use of supplements containing Spirulina]. Rinsho Shinkeigaku 2011;51(5):330-333. PubMed
  13. Le TM, Knulst AC, Röckmann H. Anaphylaxis to Spirulina confirmed by skin prick test with ingredients of Spirulina tablets. Food Chem Toxicol 2014;74:309-10. PubMed
  14. Rzymski P, Niedzielski P, Kaczmarek N, Jurczak T, Klimaszyk P. The multidisciplinary approach to safety and toxicity assessment of microalgae-based food supplements following clinical cases of poisoning. Harmful Algae 2015;46:34-42. DOI
  15. Petrus M, Culerrier R, Campistron M, et al. First case report of anaphylaxis to spirulin: identification of phycocyanin as responsible allergen. Allergy 2010;65(7):924-5. 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 Blue-green Algae and Macitentan Together: Common Questions

Is it safe to take Blue-green Algae with Macitentan?
We do not list a known interaction between Blue-green Algae and Macitentan. 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 Blue-green Algae and Macitentan have any of the same side effects?
Yes — our sources link each of them separately to 6 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 Blue-green Algae and Macitentan 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 Blue-green Algae in each. That is a conversation for your prescriber, especially if Macitentan is being adjusted to a target.
How was the Blue-green Algae and Macitentan combination checked?
Interactions in our licensed database are recorded against drug classes. Macitentan is filed under 4 classifications, and Blue-green Algae has documented interactions with 3 drug classes — none of Macitentan'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 Blue-green Algae interact with any other medications?
Yes. Blue-green Algae has 327 documented drug interactions in our database — Macitentan 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 Macitentan interact with any supplements?
Yes. Macitentan has documented interactions with 253 supplements in our database — Blue-green Algae is not one of them. The Macitentan 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

Blue-green Algae monograph Uses, safety profile, and every drug interaction in one place Macitentan drug information The full plain-English guide to this medication Macitentan supplement interactions Every supplement checked against Macitentan, 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 22 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Macitentan and Blue-green Algae?

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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.