Drug & supplement interaction

L-arginine + Mepolizumab

Mepolizumab brand name: Nucala.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between L-arginine and Mepolizumab 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

L-arginine and Mepolizumab

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 Mepolizumab and L-arginine 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.

L-arginine safety at a glance

L-arginine overall Use caution Often well tolerated short-term, but it can lower blood pressure and may not be safe for everyone.
Pregnancy Possibly Safe When used orally and appropriately, short-term. L-arginine 12 grams daily for 2 days has been used with apparent safety in pregnancy during the third trimester.... Read the full pregnancy detail
Breastfeeding Not established There is not enough reliable information, so it is best avoided unless your doctor advises otherwise.

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Mepolizumab and L-arginine? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
Keep it in perspective

L-arginine Does Interact With Other Medications

L-arginine has 395 moderate, 8 minor known drug interactions in our database — Mepolizumab isn’t one of them. If you take anything else, check it against the full list below.

Moderate 395 Minor 8 No known interaction 2,427 (incl. Mepolizumab)
Taking anything else?

Check Another of Your Medications Against L-arginine

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

What to actually watch for

No Interaction Found — But Data Suggests L-arginine and Mepolizumab 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.

  • Wheezing Worth acting on reported in 40.3% of FDA reports for Mepolizumab Additional detail

    L-arginine

    “When inhaled, L-arginine can cause airway inflammation and exacerbation of airway inflammation in asthma. However, two studies assessing oral L-arginine in patients with asthma did not detect any adverse airway effects.”

    L-arginine · Natural Medicines adverse-effect record, reported in asthma.

    3 sources cited
    1. 121. Sapienza MA, Kharitonov SA, Horvath I, et al. Effect of inhaled L-arginine on exhaled nitric oxide in normal and asthmatic subjects. Thorax 1998;53:172-5.
    2. 31849. de Gouw, H. W., Verbruggen, M. B., Twiss, I. M., and Sterk, P. J. Effect of oral L-arginine on airway hyperresponsiveness to histamine in asthma. Thorax 1999;54(11):1033-1035. PubMed
    3. 104223. Liao SY, Showalter MR, Linderholm AL, et al. l-Arginine supplementation in severe asthma. JCI Insight. 2020;5(13):e137777. PubMed

    Mepolizumab

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

  • An allergic reaction Worth acting on Additional detail

    L-arginine

    “Orally, arginine can cause flushing, rash, and hives. The skin reactions were likely of allergic etiology as oral L-arginine has been associated with eosinophilia. In one case report, intravenous administration caused allergic reactions including urticaria, periorbital edema, and pruritus. Excessively rapid infusion of L-arginine has caused flushing, local venous irritation, numbness.”

    L-arginine · Natural Medicines adverse-effect record, reported in pruritus.

    6 sources cited
    1. 3460. Korting GE, Smith SD, Wheeler MA, et al. A randomized double-blind trial of oral L-arginine for treatment of interstitial cystitis. J Urol 1999;161:558-65. DOI
    2. 32138. Fontanive P, Saponati G, Iurato A, et al. Effects of L-arginine on the Minnesota Living with Heart Failure Questionnaire quality-of-life score in patients with chronic systolic heart failure. Med.Sci.Monit. 2009;15:CR606-11.
    3. 102587. Gallo L, Pecoraro S, Sarnacchiaro P, Silvani M, Antonini G. The daily therapy with L-arginine 2,500 mg and tadalafil 5 mg in combination and in monotherapy for the treatment of erectile dysfunction: A prospective, randomized multicentre study. Sex Med. 20 PubMed
    4. 104223. Liao SY, Showalter MR, Linderholm AL, et al. l-Arginine supplementation in severe asthma. JCI Insight. 2020;5(13):e137777. PubMed
    5. 11830. Resnick DJ, Softness B, Murphy AR, et al. Case report of an anaphylactoid reaction to arginine. Ann Allergy Asthma Immunol 2002;88:67-8. PubMed
    6. 3330. Tenenbaum A, Fisman EZ, Motro M. L-arginine: Rediscovery in progress. Cardiology 1998;90:153-9.

    Mepolizumab

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

  • Back pain Additional detail

    L-arginine

    “Intravenous L-arginine has been associated with lower back pain and leg restlessness. Orally, L-arginine has been associated with asthenia.”

    L-arginine · Natural Medicines adverse-effect record, reported in back pain.

    2 sources cited
    1. 32273. Schellong, S. M., Boger, R. H., Burchert, W., Bode-Boger, S. M., Galland, A., Frolich, J. C., Hundeshagen, H., and Alexander, K. Dose-related effect of intravenous L-arginine on muscular blood flow of the calf in patients with peripheral vascular disease
    2. 32138. Fontanive P, Saponati G, Iurato A, et al. Effects of L-arginine on the Minnesota Living with Heart Failure Questionnaire quality-of-life score in patients with chronic systolic heart failure. Med.Sci.Monit. 2009;15:CR606-11.

    Mepolizumab

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

  • Itching Additional detail

    L-arginine

    Recorded for L-arginine in the same Natural Medicines adverse-effect record shown under An allergic reaction above.

    Mepolizumab

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

  • Stomach pain Additional detail

    L-arginine

    “Oral, intravenous, and topical L-arginine are generally well tolerated.

    Most Common Adverse Effects:

    Orally: Abdominal pain, bloating, nausea, diarrhea, headache, insomnia, flushing.

    Intravenously: Excessively rapid infusion can cause flushing, headache, nausea and vomiting, numbness, and venous irritation.”

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

    Mepolizumab

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

  • Tiredness Additional detail

    L-arginine

    “Orally, L-arginine has been associated with headache, insomnia, fatigue, and vertigo.”

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

    6 sources cited
    1. 31855. Cartledge, J. J., Davies, A. M., and Eardley, I. A randomized double-blind placebo-controlled crossover trial of the efficacy of L-arginine in the treatment of interstitial cystitis. BJU.Int. 2000;85(4):421-426.
    2. 31955. Mansoor, J. K., Morrissey, B. M., Walby, W. F., Yoneda, K. Y., Juarez, M., Kajekar, R., Severinghaus, J. W., Eldridge, M. W., and Schelegle, E. S. L-arginine supplementation enhances exhaled NO, breath condensate VEGF, and headache at 4,342 m. High Alt.M
    3. 32261. Khan, F., Litchfield, S. J., McLaren, M., Veale, D. J., Littleford, R. C., and Belch, J. J. Oral L-arginine supplementation and cutaneous vascular responses in patients with primary Raynaud's phenomenon. Arthritis Rheum. 1997;40(2):352-357.
    4. 91197. Vadillo-Ortega F, Perichart-Perera O, Espino S, et al. Effect of supplementation during pregnancy with L-arginine and antioxidant vitamins in medical food on pre-eclampsia in high risk population: randomised controlled trial. BMJ. 2011 May 19;342:d2901. PubMed
    5. 102587. Gallo L, Pecoraro S, Sarnacchiaro P, Silvani M, Antonini G. The daily therapy with L-arginine 2,500 mg and tadalafil 5 mg in combination and in monotherapy for the treatment of erectile dysfunction: A prospective, randomized multicentre study. Sex Med. 20 PubMed
    6. 102592. El-Wakeel LM, Fouad FA, Saleem MD, Saber-Khalaf M. Efficacy and tolerability of sildenafil/l-arginine combination relative to sildenafil alone in patients with organic erectile dysfunction. Andrology. 2020;8(1):143-147.

    Mepolizumab

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

  • Diarrhea Additional detail

    L-arginine

    “Orally, L-arginine has been reported to cause nausea, diarrhea, vomiting, dyspepsia, gastrointestinal discomfort, and bloating.

    Orally, L-arginine has been reported to cause esophagitis in at least six adolescents. Symptoms, which included pain and dysphagia, occurred within 1-3 months of treatment in most cases. There are at least two cases of acute pancreatitis possibly associated with oral L-arginine.”

    L-arginine · Natural Medicines adverse-effect record, reported in diarrhea.

    6 sources cited
    1. 1363. Clarkson P, Adams MR, Powe AJ, et al. Oral L-arginine improves endothelium-dependent dilation in hypercholesterolemic young adults. J Clin Invest 1996;97:1989-94. PubMed
    2. 31855. Cartledge, J. J., Davies, A. M., and Eardley, I. A randomized double-blind placebo-controlled crossover trial of the efficacy of L-arginine in the treatment of interstitial cystitis. BJU.Int. 2000;85(4):421-426.
    3. 31871. Nagaya, N., Uematsu, M., Oya, H., Sato, N., Sakamaki, F., Kyotani, S., Ueno, K., Nakanishi, N., Yamagishi, M., and Miyatake, K. Short-term oral administration of L-arginine improves hemodynamics and exercise capacity in patients with precapillary pulmona
    4. 31972. Savoye, G., Jemaa, Y., Mosni, G., Savoye-Collet, C., Morcamp, P., Dechelotte, P., Bouin, M., Denis, P., and Ducrotte, P. Effects of intragastric L-arginine administration on proximal stomach tone under basal conditions and after an intragastric diet. Dig PubMed
    5. 31978. Facchinetti, F., Saade, G. R., Neri, I., Pizzi, C., Longo, M., and Volpe, A. L-arginine supplementation in patients with gestational hypertension: a pilot study. Hypertens.Pregnancy. 2007;26(1):121-130. PubMed
    6. 32261. Khan, F., Litchfield, S. J., McLaren, M., Veale, D. J., Littleford, R. C., and Belch, J. J. Oral L-arginine supplementation and cutaneous vascular responses in patients with primary Raynaud's phenomenon. Arthritis Rheum. 1997;40(2):352-357.

    Mepolizumab

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

  • Headache Additional detail

    L-arginine

    Recorded for L-arginine in the same Natural Medicines adverse-effect record shown under Stomach pain above.

    Mepolizumab

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

Reported for L-arginine but not commonly for Mepolizumab: stomach upset, pancreatitis, anxiety or restlessness and sweating.

Effects for Mepolizumab come from the ADVERSE REACTIONS section of its FDA label; effects for L-arginine come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 49,399 voluntary FDA FAERS reports for Mepolizumab 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.

Special populations

L-arginine in Pregnancy & Breastfeeding

Pregnancy Possibly Safe

When used orally and appropriately, short-term. L-arginine 12 grams daily for 2 days has been used with apparent safety in pregnancy during the third trimester. L-arginine 3 grams daily has been taken safely during the second and/or third trimesters. ...when used intravenously and appropriately, short-term. Intravenous L-arginine 20-30 grams daily has been used safely in pregnancy for up to 5 days.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

From our Q&A

Questions About L-arginine or Mepolizumab

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

One more smart check

Taking L-arginine as Part of a Dietary Supplement Product? Check It for Interactions

We hold 26 real supplement products containing L-arginine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides L-arginine. Even though L-arginine itself has no known interaction with Mepolizumab, 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 L-arginine and Mepolizumab 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 L-arginine
Steady interest

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

29 days ago today
Medication Mepolizumab
Top half

#1,411 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 L-arginine reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The L-arginine and Mepolizumab records this page draws on were last updated July 11, 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 L-arginine

What is L-arginine?

L-arginine
  • High blood pressure
  • Erectile dysfunction
  • Athletic performance
  • Chest pain (angina)
  • Improving blood flow

L-arginine is an amino acid that the body uses to make nitric oxide, a substance that helps blood vessels relax and widen. It is popularly used for blood pressure, erectile dysfunction, and exercise, but the evidence is mixed and stronger for some uses than others. It is generally well tolerated in healthy adults, but talk with a pharmacist or doctor before using it, especially if you have heart problems or take other medicines.

Amino acid (made by the body and found in protein-rich foods) · Capsules, tablets, powders, sustained-release products

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

L-arginine: dosing

There is no single official dose of L-arginine that fits all uses, and the amounts used in studies have varied widely. Because of this, a standardized dose is often not established.The best approach is to follow the directions on the product label and to start with the lowest reasonable amount. A pharmacist can help you decide whether a product and dose make sense for your situation.Do not assume that more is better. Higher doses are more likely to cause stomach upset and other side effects.

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

Read the full L-arginine monograph & all interactions
Medication

About Mepolizumab Injection

What Is Mepolizumab Injection Used For?

Brand name: Nucala

Nucala is used as an add-on maintenance treatment — meaning it works alongside other medications, not instead of them. It is approved for severe asthma (in patients 6 years and older with high eosinophil levels), chronic rhinosinusitis with nasal polyps (CRSwNP) in adults 18 and older whose symptoms aren't controlled by nasal corticosteroids alone, and COPD in adults with an eosinophilic phenotype whose disease isn't adequately controlled.

Nucala is also approved to treat eosinophilic granulomatosis with polyangiitis (EGPA), a rare form of blood vessel inflammation, and hypereosinophilic syndrome (HES), a condition involving dangerously elevated eosinophil counts, in adults and adolescents 12 and older. It is not meant to relieve sudden asthma attacks or acute COPD flares.

Most-Reported Side Effects for Mepolizumab

From FAERS, the FDA’s public side-effect reporting system (49,399 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Asthma 12,767 reports
Dyspnea 10,576 reports
Wheezing 7,131 reports
Cough 5,100 reports
Therapeutic product effect incomplete 5,051 reports
See full Mepolizumab Injection drug information
Keep checking

Other Drugs & L-arginine

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

0Major
395Moderate
8Minor
2,426No known interaction
395 Moderate 8 Minor 2,426 No interaction
Moderate

395 interactions

Showing 60 of 395 moderate interactions — see all 395 on the L-arginine page.

Minor

8 interactions

No interaction 2,426 drugs checked — show the list

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

Showing the 60 most looked-up of 2,426 medications checked with no known interaction — see the full L-arginine list.

See the full L-arginine interactions page
See every supplement checked against Mepolizumab, ranked by severity
Evidence & sources

L-arginine References

The 66 references that drive our L-arginine 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. Sapienza MA, Kharitonov SA, Horvath I, et al. Effect of inhaled L-arginine on exhaled nitric oxide in normal and asthmatic subjects. Thorax 1998;53:172-5.
  2. Clarkson P, Adams MR, Powe AJ, et al. Oral L-arginine improves endothelium-dependent dilation in hypercholesterolemic young adults. J Clin Invest 1996;97:1989-94. PubMed
  3. Tenenbaum A, Fisman EZ, Motro M. L-arginine: Rediscovery in progress. Cardiology 1998;90:153-9.
  4. Brittenden J, Park KGM, Heys SD, et al. L-Arginine stimulates host defenses in patients with breast cancer. Surgery 1994;115:205-12.
  5. Korting GE, Smith SD, Wheeler MA, et al. A randomized double-blind trial of oral L-arginine for treatment of interstitial cystitis. J Urol 1999;161:558-65. DOI
  6. Rector TS, Bank AJ, Mullen KA, et al. Randomized, double-blind, placebo-controlled study of supplemental oral L-arginine in patients with heart failure. Circulation 1996;93:2135-41.
  7. Siani A, Pagano E, Iacone R, et al. Blood pressure and metabolic changes during dietary L-arginine supplementation in humans. Am J Hypertens 2000;13:547-51. PubMed
  8. Cheng JW, Balwin SN. L-arginine in the management of cardiovascular diseases. Ann Pharmacother 2001;35:755-64. PubMed
  9. Wallace AW, Tom WL. Interaction of L-arginine and phosphodiesterase inhibitors in vasodilation of the porcine internal mammary artery. Anesth Analg 2000;90:840-6. DOI
  10. Huynh NT, Tayek JA. Oral arginine reduces systemic blood pressure in type 2 diabetes: its potential role in nitric oxide generation. J Am Coll Nutr 2002;21:422-7.. PubMed
  11. Staff AC, Berge L, Haugen G, et al. Dietary supplementation with L-arginine or placebo in women with pre-eclampsia. Acta Obstet Gynecol Scand 2004;83:103-7.
  12. Resnick DJ, Softness B, Murphy AR, et al. Case report of an anaphylactoid reaction to arginine. Ann Allergy Asthma Immunol 2002;88:67-8. PubMed
  13. Anon. Arginine hydrochloride injection (marketed as R-Gene 10). FDA Drug Safety Newsletter 2009;2(2):16-18. Available at: www.fda.gov/Drugs/DrugSafety/DrugSafetyNewsletter/default.htm.
  14. Higashi Y, Oshima T, Sasaki S, et. al. Angiotensin-converting enzyme inhibition, but not calcium antagonism, improves a response of the renal vasculature to L-arginine in patients with essential hypertension. Hypertension. 1998 Jul;32(1):16-24.
  15. Facchinetti, F., Longo, M., Piccinini, F., Neri, I., and Volpe, A. L-arginine infusion reduces blood pressure in preeclamptic women through nitric oxide release. J Soc Gynecol.Investig. 1999;6(4):202-207. DOI

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 L-arginine and Mepolizumab Together: Common Questions

Is it safe to take L-arginine with Mepolizumab?
We do not list a known interaction between L-arginine and Mepolizumab. 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 L-arginine and Mepolizumab have any of the same side effects?
Yes — our sources link each of them separately to 8 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.
Does L-arginine interact with any other medications?
Yes. L-arginine has 403 documented drug interactions in our database — Mepolizumab is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

L-arginine monograph Uses, safety profile, and every drug interaction in one place Mepolizumab Injection drug information The full plain-English guide to this medication Mepolizumab supplement interactions Every supplement checked against Mepolizumab, 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 66 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Mepolizumab and L-arginine?

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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.