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- Key facts
- How nitric oxide creates an erection
- NO booster vs prescription PDE5
- What L-arginine and L-citrulline trials show
- Beet juice and dietary nitrate
- FDA warnings on hidden ingredients
- Nitrate drugs are different
- What each path includes
- Label hard stops
- If ED is the problem you want treated now
- Mendoxa plans and prices
- FAQ
- How we wrote this
- Sources and references
Key facts at a glance
- Mechanism
- Sexual stimulation releases NO, which raises cGMP and lets blood flow in; sildenafil blocks PDE5, which breaks cGMP downViagra (sildenafil) label · DailyMed
- L-arginine
- 10 randomized trials, 540 men with mild to moderate ED; arginine alone and combination supplements were includedRhim et al. 2019 · PubMed
- L-citrulline
- Hardness improved in 12 of 24 men with mild ED vs 2 of 24 on placeboCormio et al. 2011 · PubMed
- Nitrate drugs
- Sildenafil is contraindicated with nitric oxide donors such as nitroglycerinViagra (sildenafil) label · DailyMed
- Compounded status
- The Mendoxa compounded tablet is not FDA-approvedFDA compounding Q&A
How nitric oxide creates an erection
Arousal → nitric oxide → cGMP → increased blood flow. In Clinical Pharmacology, the Viagra (sildenafil) label says NO “activates the enzyme guanylate cyclase,” raising cGMP and relaxing penile smooth muscle. The Cialis (tadalafil) label identifies NO release “from nerve terminals and endothelial cells.”
PDE5 breaks down cGMP; sildenafil and tadalafil inhibit PDE5. This helps preserve the response to sexual stimulation, rather than supplying nitric oxide. Both labels explain that the medicines have no effect without sexual stimulation (Viagra (sildenafil) label; Cialis (tadalafil) label). See our sildenafil guide and tadalafil guide for the individual medicines.
NO booster vs prescription PDE5 medicine
A supplement study and an FDA-approved prescription label answer different questions. The Viagra (sildenafil) label and Cialis (tadalafil) label establish approved uses for the separate medicines; the supplement results below describe specific study populations.
| Option | How it works | Evidence quality | FDA status | Onset / timing per label |
|---|---|---|---|---|
| L-arginine supplement | Building block the body uses to make NO | Meta-analysis of 10 small RCTs, mild to moderate ED only (Rhim 2019) | Dietary supplement; not FDA-approved to treat ED | No FDA label |
| L-citrulline supplement | Converted to L-arginine, then used to make NO (Cormio 2011) | Standalone single-blind study of 24 men with mild ED (Cormio 2011) | Dietary supplement; not FDA-approved to treat ED | No FDA label |
| Dietary nitrate (beet juice) | Proposed NO source from food | ED benefit not established by the studies summarized here; research registration (NCT04116060) | Food; not FDA-approved to treat ED | No FDA label |
| Sildenafil (Viagra) | Blocks PDE5 so cGMP lasts longer | FDA-approved after controlled trials (Viagra (sildenafil) label) | FDA-approved prescription medicine | Taken about 1 hour before sex; label range 30 minutes to 4 hours (Viagra (sildenafil) label) |
| Tadalafil (Cialis) | Blocks PDE5 so cGMP lasts longer | FDA-approved after controlled trials (Cialis (tadalafil) label) | FDA-approved prescription medicine | Duration, not onset: improved erectile function vs placebo up to 36 hours after dosing (Cialis (tadalafil) label) |
Sources: Viagra (sildenafil) label; Cialis (tadalafil) label; Rhim et al. 2019; Cormio et al. 2011; ClinicalTrials.gov NCT04116060. Accessed Oct 24, 2026.
Administration timing differs from onset. The sildenafil entry gives the label’s administration window; the tadalafil entry describes how long benefit was demonstrated, not how quickly it starts (Viagra (sildenafil) label; Cialis (tadalafil) label). These labels do not establish the timing or effectiveness of Mendoxa’s compounded combination.
L-arginine and L-citrulline for ED: what trials actually show
These studies suggest possible benefit, with important limits. The Rhim 2019 meta-analysis pooled placebo or no-treatment comparisons; the Cormio 2011 study tested the same men through consecutive placebo and supplement phases. Neither is a direct comparison against sildenafil (Viagra (sildenafil) label).
| Study and year | Who was studied | Result | What it cannot tell you |
|---|---|---|---|
| L-arginine · Rhim et al. meta-analysis · 2019 | 10 randomized controlled trials, 540 men with mild to moderate ED | Improved ED vs placebo or no treatment: odds ratio 3.37 (95% CI 1.29–8.77). Sexual desire scores unchanged. PubMed | Doses and durations varied; the review included arginine alone and combinations. The pooled result cannot establish which retail product will work. |
| L-citrulline · Cormio et al. · 2011 | 24 men with mild ED (hardness score 3) | Hardness improved to 4 in 12 of 24 (50%) on L-citrulline vs 2 of 24 (8.3%) on placebo. PubMed | Single-blind; the same men took placebo for one month, then L-citrulline for one month; no prescription comparator arm |
Sources: Rhim HC, et al. J Sex Med 2019 (PMID 30770070); Cormio L, et al. Urology 2011 (PMID 21195829). Accessed Oct 24, 2026.
Read the outcomes literally: the arginine odds ratio is not a success percentage or a promise of stronger erections. In the citrulline study, 12 men improved out of 24 enrolled; they were not separate groups of 24. Its fixed treatment order limits what we can attribute to the supplement (Rhim 2019 meta-analysis; Cormio 2011 study).
For other ingredients and product selection, use our supplements for ED guide. This page focuses on the nitric oxide pathway and what these specific studies can support.
Beet juice and dietary nitrate: evidence status
Beet juice is not established as a substitute for prescription ED treatment by the evidence reviewed here. The arginine and citrulline studies tested different interventions, so their results cannot be transferred to beet juice (Rhim 2019 meta-analysis; Cormio 2011 study). A dietary-nitrate ED study registration is a research lead, not proof of benefit.
For practical next steps beyond supplements, explore home remedies for ED and how to get harder erections.
Food nitrate and prescription nitrate drugs are different categories. The contraindication in the Viagra (sildenafil) label concerns organic nitrate or nitrite drugs, including nitroglycerin; it should not be read as a warning to avoid vegetables.
FDA warnings: hidden sildenafil in “natural” boosters
“Natural” on a sexual enhancement product does not establish its contents. FDA’s sexual enhancement notifications identify products with hidden drug ingredients; the examples below are specific FDA findings, not a claim about every NO supplement.
| FDA notice and date | Hidden ingredient found by FDA | FDA warning |
|---|---|---|
| FDA: X10 — hidden sildenafil and tadalafil · May 29, 2026 | Sildenafil and tadalafil not listed on the label | May interact with nitrates such as nitroglycerin and lower blood pressure to dangerous levels |
| FDA: 10 Day Forecast — hidden sildenafil and acetaminophen · Oct 15, 2026 | Sildenafil and acetaminophen not listed on the label | Sildenafil may interact with nitrates such as nitroglycerin; acetaminophen can cause liver damage |
Sources: FDA: sildenafil and tadalafil in X10; FDA: sildenafil and acetaminophen in 10 Day Forecast; FDA notification list; NIH NCCIH. Accessed Oct 24, 2026.
FDA cautions that absence from its notification list does not establish safety. Hidden sildenafil or tadalafil matters because these medicines are contraindicated with nitrate drugs (Viagra (sildenafil) label; Cialis (tadalafil) label). Our Rhino pills guide covers another product category flagged for hidden ingredients.
Nitroglycerin and “poppers” are a different thing
Do not combine nitrate drugs or “poppers” with sildenafil or tadalafil. The Viagra (sildenafil) label contraindicates organic nitrates and nitrites because the combination can dangerously lower blood pressure; its patient information names nitroglycerin and poppers. The Cialis (tadalafil) label also contraindicates organic nitrates.
If you use or carry nitroglycerin, tell the provider before discussing ED medication (Viagra (sildenafil) label; Cialis (tadalafil) label). Read our ED and nitrates guide before choosing a treatment path.
What each path includes
Use your next decision to choose the path. If you want to discuss treatment for recurring erection difficulties, bring your medication and supplement list to an online assessment. Independent licensed providers decide whether a prescription is appropriate.
| Your priority | Starting point | What it includes | Boundary |
|---|---|---|---|
| Understand supplement evidence | L-arginine or L-citrulline | Small-trial evidence in mild to moderate ED (Rhim 2019; Cormio 2011) | FDA warns some sexual enhancement products hide drug ingredients (FDA notices) |
| Change daily habits | Diet, exercise, sleep, alcohol | Steps in our home remedies guide | Use the guide to prepare questions for your visit |
| Discuss a standalone ED prescription | Online visit or in-person clinician | Sildenafil or tadalafil if suitable (Viagra (sildenafil) label; Cialis (tadalafil) label) | Prescription required; contraindicated with nitrates |
| Ask whether Mendoxa fits | Mendoxa online assessment | Independent licensed providers review your history for the compounded 3-in-1 tablet | Compounded drugs are not FDA-approved |
Sources: Rhim 2019; Cormio 2011; FDA notification list; Viagra (sildenafil) label; Cialis (tadalafil) label; FDA compounding Q&A; Mendoxa care information. Accessed Oct 24, 2026.
Before a visit, list every supplement you take as well as your medicines; compare ED medication options if you are still deciding.
Prepare for the visit: describe what happens when you try to get or keep an erection, what you have already tried, and what you want from treatment. Bring product names or ingredient lists so the provider can assess the actual products.
Could Mendoxa ED care fit you?
Online ED visit · Prescription required · Independent licensed providers · Not available in California
Label hard stops
Label hard stops (nitrates, riociguat, an erection over 4 hours, sudden vision or hearing loss) are listed once in our sildenafil guide, from the Viagra (sildenafil) label and Cialis (tadalafil) label.
If ED is the problem you want treated now
Take the next step with a private online assessment. Share your symptoms, health history, medicines and supplements. Independent licensed providers decide whether treatment is appropriate. Prescription required. Mendoxa ED care explains the process.
Mendoxa offers a compounded rapid-dissolve tablet containing sildenafil, tadalafil and apomorphine. It is not FDA-approved. The Viagra (sildenafil) label, Cialis (tadalafil) label and APOKYN (apomorphine) label concern separate products; APOKYN is an injectable Parkinson’s treatment, and its label is not approval of this ED combination.
Before deciding, read about the compounded combination ED tablet. Use the online visit to ask why a compounded option might fit your needs and what alternatives are appropriate. Costs below apply if prescribed.
Mendoxa ED plans and prices
The Mendoxa ED tablet is a compounded rapid-dissolve tablet with sildenafil (the active ingredient in Viagra), tadalafil (the active ingredient in Cialis) and apomorphine (APOKYN label). It dissolves under the tongue. A licensed clinician decides if it fits you and selects the strength. Compounded medicines are not FDA-approved.
| Tablets per month | 1-month total | Per tablet (1 month) | 3-month total | Per tablet (3 months) |
|---|---|---|---|---|
| 6 tablets / month | $129 | $21.50 | $329 | $18.28 |
| 10 tablets / month | $149 | $14.90 | $379 | $12.63 |
| 20 tablets / month | $179 | $8.95 | $449 | $7.48 |
The 3-month total covers three months at the monthly tablet quantity shown.
If prescribed · Cancel anytime · Available in 49 states (not California). Prices from the Mendoxa intake at try.mendoxa.co/f/ed on Oct 24, 2026. The intake always shows the current price.
FAQ
Does nitric oxide help with ED?
Nitric oxide helps mediate the erectile response, according to the Viagra (sildenafil) label. Supplements meant to raise it have only small-trial support in mild to moderate ED (Rhim 2019; Cormio 2011).
Can a nitric oxide supplement replace Viagra?
The studies summarized here do not establish that a supplement can replace Viagra: they compare supplements with placebo or no treatment (Rhim 2019 meta-analysis; Cormio 2011 study). Sildenafil is a prescription ED medicine with an FDA-approved label (Viagra (sildenafil) label).
Is L-arginine or L-citrulline better for ED?
These studies do not settle that comparison. Arginine has a meta-analysis of 10 trials involving 540 participants (Rhim 2019 meta-analysis); the standalone citrulline study enrolled 24 men (Cormio 2011 study). Different designs and outcomes prevent a reliable ranking.
Can I take L-arginine with Viagra or Cialis?
Ask your prescriber before combining them, and bring the exact product label. The Viagra (sildenafil) label asks patients to report vitamins, herbal supplements and other ED treatments; neither it nor the Cialis (tadalafil) label establishes that a retail NO-booster combination is safe for you.
Does beet juice work like Viagra?
The evidence reviewed here does not establish that beet juice works like Viagra. Arginine and citrulline results cannot be applied to beet juice (Rhim 2019 meta-analysis; Cormio 2011 study); sildenafil works by inhibiting PDE5 (Viagra (sildenafil) label).
Are nitric oxide supplements the same as nitrates?
No. Prescription nitrates such as nitroglycerin are NO donor drugs, and the Viagra (sildenafil) label contraindicates them with sildenafil. Read our ED and nitrates guide.
Ready to see if the Mendoxa ED tablet fits you?
From $129/month if prescribed · Cancel anytime · Available in 49 states (not California)
How we wrote this
Written by the Mendoxa editorial team · Sources: DailyMed/FDA. Medical facts on this page come from the FDA-approved labels on DailyMed and Drugs@FDA; each drug name links to its label. We checked DailyMed/FDA labels and PubMed abstracts on Oct 24, 2026. The tables distinguish study results from editorial interpretation, and administration timing from duration of benefit. The Viagra (sildenafil) label, Cialis (tadalafil) label and APOKYN (apomorphine) label concern separate approved products; they do not establish the safety or effectiveness of the compounded ED combination. APOKYN is an injection for Parkinson’s disease. Question themes inform the FAQ, not its medical answers.
Updated Oct 24, 2026. This page is general information, not medical advice. A licensed clinician decides what fits you.
References
- DailyMed: VIAGRA (sildenafil citrate) tablet, film coated, label revised 12/2017. Accessed Oct 24, 2026.
- DailyMed: CIALIS (tadalafil) tablet, film coated, label revised 3/2026. Accessed Oct 24, 2026.
- DailyMed: APOKYN (apomorphine hydrochloride) injection, label revised 6/2022. Accessed Oct 24, 2026.
- FDA (Drugs@FDA): VIAGRA (sildenafil) prescribing information, NDA 020895. Accessed Oct 24, 2026.
- FDA (Drugs@FDA): CIALIS (tadalafil) prescribing information, NDA 021368. Accessed Oct 24, 2026.
- FDA: Compounding and the FDA, questions and answers. Accessed Oct 24, 2026.
- Rhim HC, et al. The Potential Role of Arginine Supplements on Erectile Dysfunction: A Systemic Review and Meta-Analysis. J Sex Med. 2019;16(2):223-234. PMID 30770070. Accessed Oct 24, 2026.
- Cormio L, et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology. 2011;77(1):119-22. PMID 21195829. Accessed Oct 24, 2026.
- ClinicalTrials.gov: Dietary Nitrate and Erectile Dysfunction (NCT04116060). Accessed Oct 24, 2026.
- FDA: Sexual enhancement and energy product notifications. Accessed Oct 24, 2026.
- FDA: X10 Natural Enhancement Supplement may be harmful due to hidden drug ingredients (May 29, 2026). Accessed Oct 24, 2026.
- FDA: 10 Day Forecast may be harmful due to hidden ingredients (Oct 15, 2026). Accessed Oct 24, 2026.
- NIH NCCIH: dietary supplements marketed for sexual enhancement. Accessed Oct 24, 2026.
- Mendoxa ED care (product, format, max 1 dose per 24 hours). Accessed Oct 24, 2026.
- Mendoxa ED intake: plan prices (term_options). Accessed Oct 24, 2026.
About Mendoxa
Mendoxa (mendoxa.co) is a US telehealth brand. Independent licensed providers (licensed clinicians in the LocumTele network) review each online visit, and prescriptions are filled by Rush Pharmacy, a licensed US pharmacy. Available in 49 states (not California).
- Prescription required. A licensed clinician reviews every visit and can say no. A prescription is not automatic.
- A compounded medicine is not an FDA-approved finished product (FDA compounding Q&A).
- Plans: 1 month or 3 months, from $129. If prescribed · Cancel anytime · Available in 49 states (not California).
Compounded medication prescribed only if a licensed U.S. clinician decides it is appropriate. Not FDA-approved as a finished product. Not available in California. This site is not for emergencies. Call 911 if you need urgent care.