Peptides for ED and Low Libido in Men: PT-141, Kisspeptin, and What Clinicians Actually Prescribe

Key takeaways

• For erectile dysfunction, no peptide comes close to what already works. In the pivotal sildenafil trial, 69% of intercourse attempts succeeded on the drug versus 22% on placebo, and PDE5 inhibitors are now generic. Peptides enter this conversation as a distant second line, or not at all.
• ED is often an early sign of vascular disease: across cohort studies of 92,757 men, it predicted a 44% higher risk of cardiovascular events. The first step is a medical evaluation with blood pressure, glucose, lipids and a morning testosterone level, not a vial.
• Testosterone helps only when it is confirmed low, and it helps desire more than erections: two large trials found better desire and sexual activity, one found a modest gain in erectile function and the other none. TRAVERSE found no rise in heart attacks or strokes.
• PT-141 (bremelanotide) produced erections in laboratory studies of men in 2004 at 4 to 6 mg injected, but FDA named blood pressure its greatest safety concern in 2007 and it was never approved for men. It is the only libido peptide a licensed pharmacy can legally compound, and using it for ED is off-label.
• Kisspeptin has striking single-infusion data and no legal product; oxytocin spray has not changed erections in the studies that exist; melanotan II has priapism and melanoma case reports and no legal source; and no marketed stack has ever been tested as a combination.

Search for peptides for ED and you will find PT-141 nasal sprays, kisspeptin vials, oxytocin troches and 'performance stacks' that combine all three. What you will rarely find is the comparison that matters: how any of them does against the pills and hormone therapy that urologists already prescribe. This guide makes that comparison, with the trial numbers, for men. The PT-141 profile and the kisspeptin-10 profile cover each compound in full, kisspeptin vs PT-141 compares the two, and the support guides cover PT-141 dosage and how long PT-141 lasts.

How we ranked

We ranked by four things, in this order: the quality of human evidence for erections or sexual function in men, graded A to D under our editorial policy; whether a US clinician can prescribe it and a licensed pharmacy dispense it as of October 2026, consistent with our legal tracker; the safety record; and cost. Popularity did not count.

Two distinctions run through the ranking. Erections and desire are different problems. ED is mostly a matter of blood vessels and nerves; low libido is mostly a matter of hormones, the brain and circumstances, and a drug can help one without touching the other. And the benchmark is not a peptide. A ranking of peptides alone would hide the most useful answer, so the first two places go to treatments that are not peptides at all.

The ranking at a glance

Prices are October 2026 figures from our cost guide.

Start here: ED is often a vascular warning sign

Erections depend on small arteries that dilate on demand, and those arteries often show damage before the coronary arteries do. In a meta-analysis of 14 cohort studies covering 92,757 men followed for a mean of 6.1 years, men with ED had a 44% higher risk of cardiovascular events, a 62% higher risk of heart attack, a 39% higher risk of stroke and a 25% higher risk of death from any cause than men without it; the association was stronger in younger men (Vlachopoulos 2013). The American Urological Association's guideline tells clinicians to counsel every man with ED that it is a risk marker for underlying cardiovascular disease (AUA 2018).

The practical meaning is simple. A man in his forties with new ED needs his blood pressure, glucose and cholesterol checked before anyone discusses peptides, and this matters twice over for PT-141, which raises blood pressure after every dose and is contraindicated in known cardiovascular disease.

1. PDE5 inhibitors: the benchmark

Sildenafil, tadalafil, vardenafil and avanafil block the enzyme that ends an erection, so the penis responds more fully to arousal. The trial that established the class randomized men with ED of physical, psychological and mixed causes in two sequential studies. In a 24-week dose-response study of 532 men, 100 mg doubled the mean score for achieving erections, from 2.0 to 4.0 out of 5. In a 12-week dose-escalation study of 329 different men, 69% of intercourse attempts in the final four weeks were successful on sildenafil versus 22% on placebo, or 5.9 successful attempts a month versus 1.5. Headache, flushing and indigestion affected 6% to 18%, and 92% of men completed a 32-week open-label extension (Goldstein 1998).

That is grade A evidence, and the drugs are generic. The guideline makes three points that explain most apparent failures: men should be told how to take the drug for best effect, the dose should be titrated to the one that works, and sexual stimulation is still needed (AUA 2018). PDE5 inhibitors do not raise desire and must not be combined with nitrate heart medicines.

When pills fail, the next steps are still not peptides. The guideline lists vacuum erection devices, alprostadil inserted into the urethra, injections into the penis (alprostadil alone or in compounded mixtures, the 'ED injections' people search for), and penile implants, and its central principle is that any of these can be discussed as a first choice through shared decision-making (AUA 2018). Men with ED and confirmed testosterone deficiency should also be told that PDE5 inhibitors may work better combined with testosterone therapy (AUA 2018).

2. Testosterone: only when it is low, and mostly for desire

Can erectile dysfunction be caused by low testosterone? Partly. Low testosterone mainly lowers desire, and the large trials show what treating it does and does not fix.

• The Testosterone Trials. 790 men aged 65 or older with testosterone under 275 ng/dL and symptoms used testosterone gel or placebo for a year. Sexual activity, sexual desire and erectile function all improved significantly; the investigators called the benefit to sexual function moderate, and vitality and walking distance did not improve (Snyder 2016).
• TRAVERSE, sexual function. In 1,161 men aged 45 to 80 with confirmed hypogonadism and low libido, testosterone gel for up to two years improved sexual activity, hypogonadal symptoms and desire, but not erectile function (Pencina 2024).
• TRAVERSE, safety. 5,246 men aged 45 to 80 with heart disease or high cardiovascular risk and two fasting testosterone levels under 300 ng/dL were followed for a mean of 33 months. Heart attack, stroke or cardiovascular death occurred in 7.0% on testosterone and 7.3% on placebo (hazard ratio 0.96); atrial fibrillation, acute kidney injury and pulmonary embolism were more frequent on testosterone (Lincoff 2023).

So testosterone ranks second for a specific man: one with symptoms and repeatedly low morning levels, for whom it is likely to help desire and may help PDE5 inhibitors work. For a man with normal levels it is not an ED treatment. It is a Schedule III controlled substance, it suppresses the body's own sperm production (the kisspeptin profile compares it with hCG for men who want children), and it costs $28 to $60 a month for the medication or $99 to $289 all-in through telehealth.

3. PT-141 (bremelanotide): a real drug, an unfinished program in men

PT-141 came out of the observation that men given an experimental tanning peptide were having erections. It acts on melanocortin receptors in the brain rather than on penile blood flow, which is why it was tested in men whom sildenafil had failed.

What the male studies showed. In healthy men, injected doses from 0.3 to 10 mg produced statistically significant erections above 1 mg, measured with a rigidity monitor and without erotic stimulation. In men with an inadequate response to sildenafil 100 mg, defined as an erection good enough for penetration half the time or less, single injections of 4 and 6 mg produced significant erections in a placebo-controlled crossover with visual sexual stimulation (Rosen 2004). Nasal doses produced similar laboratory results, with erections starting about 30 minutes after dosing; the dosage guide sets out every studied dose.

Why it stopped there. In August 2007 Palatin and its partner announced that FDA had questioned the efficacy results and the clinical benefit, had cited blood pressure increases as its greatest safety concern, and had suggested at most a second-line role in men who do not respond to PDE5 inhibitors; the phase 3 program for men was shelved (King/Palatin 2007). The only large home-use trial in men, from 2008, now carries an expression of concern from its journal, so we do not count it; the PT-141 profile explains why. In June 2024 Palatin began a small open-label phase 2 study of about 50 PDE5 non-responders using bremelanotide co-formulated with a PDE5 inhibitor in a single injection (Urology Times 2024). We found no published results as of October 2026.

The safety facts that matter for men. The label, written from studies in women, records a rise of up to 6 mmHg systolic and 3 mmHg diastolic that peaks two to four hours after each dose, a fall in heart rate of up to 5 beats a minute, a contraindication in uncontrolled hypertension and known cardiovascular disease, nausea in 40% of women, and the statement that the drug is not indicated in men (Vyleesi label). Those small numbers in healthy women matter more in middle-aged men with ED, a group in which high blood pressure and vascular disease are common.

The dose gap. The doses that produced erections in men with ED were 4 and 6 mg injected. Compounded prescriptions for men are often 1 to 2 mg, which no study has tested; how long each dose lasts is covered in how long PT-141 lasts.

Who it might suit. A man with normal blood pressure and no cardiovascular disease, whose PDE5 inhibitor has failed at a properly titrated dose, who understands that this is off-label and has a prescriber checking his blood pressure. Even for him, penile injections have a stronger evidence base. Legally, bremelanotide is the active ingredient of an approved drug, so a 503A pharmacy can compound it on a prescription; vendors selling 'research' PT-141 were among those FDA warned in August 2026. Compounded PT-141 costs about $60 to $200 a month.

4. Kisspeptin: interesting brain data, no product

Kisspeptin is the hormone that switches on the reproductive axis, and it also acts in brain regions involved in sexual motivation. Its best result in men comes from a randomized crossover trial in 32 men with hypoactive sexual desire disorder, mean age 38. During a single 75-minute intravenous infusion of kisspeptin-54, brain activity in the sexual-processing network changed on MRI (the primary outcome), penile tumescence while watching sexual videos was up to 56% greater than on placebo, and 'happiness about sex' rose by 0.63 points (Mills 2023).

Three limits keep it at grade C for ED. The men had low desire, not erectile dysfunction. The effect was measured during one infusion in a scanner, never at home and never with repeated doses. And the product sold online is kisspeptin-10 for self-injection, a different form, route and schedule. Kisspeptin-10 has been in FDA's Category 2 since September 2023, FDA's compounding committee voted 0 to 11 against it in October 2024, and no pharmacy may legally prepare it; repeated dosing also blunts its hormone effect. The kisspeptin-10 profile has the detail.

5. Oxytocin nasal spray: no effect on erections in the studies that exist

Oxytocin is the bonding hormone released around orgasm, and compounded nasal sprays and troches are marketed for intimacy and arousal. The largest study in men is a crossover trial in 29 healthy heterosexual couples who used 24 IU of intranasal oxytocin or placebo before sex in a naturalistic setting. Oxytocin did not change sexual drive, arousal or penile erection; it modestly increased the intensity of orgasm and contentment afterward, effects that were somewhat larger in men (Behnia 2014). We found no randomized trial of oxytocin in men with ED.

Oxytocin is the active ingredient of FDA-approved injections used in labor, so a pharmacy can compound it on a prescription; using it for sex is off-label and untested at the doses sold. For ED it rates a D: the evidence there is says it does not do what it is sold for.

6. Melanotan II: the one to avoid

Melanotan II is PT-141's parent compound, a tanning peptide that differs from bremelanotide by one chemical group. In a 10-man placebo-controlled crossover in men with physical risk factors for ED, injections of 0.025 mg/kg produced erections after 12 of 19 doses versus 1 of 21 placebo doses and raised reported desire; nausea and yawning were common, and 4 of 19 injections caused severe nausea (Wessells 2000). An earlier 10-man study found the same in psychogenic ED (the history is in the PT-141 profile). Nothing has been tested since.

What has accumulated instead are case reports. A man developed ischemic priapism after injecting melanotan II, failed aspiration and drug treatment, and needed surgery; the authors counted two earlier published cases (Mallory 2021). A 2017 review found reports of changing moles and new atypical moles in users, plus four melanomas arising during or shortly after use; causation is not proven, and several national health agencies have issued warnings (Habbema 2017).

Melanotan II was never approved anywhere. FDA removed it from Category 2 in April 2026 after its nominator withdrew, which did not make it compoundable; it is not on the permitted list and awaits committee review by February 2027. Everything sold today is a research or tanning product with no legal status for human use.

7. The stacks sold online

Three kinds of combination are on the market in 2026:

• Compounded troches that put tadalafil, oxytocin and bremelanotide in one lozenge, sold by telehealth programs. Each ingredient can be compounded on its own, but nobody has tested the combination, and we found no published data on how much bremelanotide is absorbed through the mouth.
• Research-vial bundles pairing PT-141 with kisspeptin-10 or melanotan II. Neither partner can be legally compounded, so these stacks have no legal version at all, and FDA's 2026 warning letters rejected 'research use only' labels as a defense.
• PT-141 added to a prescribed PDE5 pill. The one published test of this idea gave 19 men low-dose nasal PT-141 with low-dose sildenafil in a laboratory and found a larger erectile response than sildenafil alone (see the PT-141 profile). The two drugs push blood pressure in opposite directions, and no one has studied the combination at compounded doses.

A stack is only as good as its weakest ingredient's evidence and only as legal as its least legal ingredient. That puts every marketed stack at grade D.

What we excluded and why

• Growth hormone secretagogues sold for 'vitality' (sermorelin, CJC-1295 with ipamorelin): no trial has measured erections or desire; see the sermorelin profile and the muscle guide.
• BPC-157 for 'blood flow': animal data only, and not legally compoundable in October 2026; see the legal tracker.
• Flibanserin and the Vyleesi label itself: approved for women's low desire, not for men; see PT-141 for women.
• Supplements, shockwave therapy and platelet-rich plasma: not peptides, and outside the scope of this guide.

How to get evaluated, and what tests to expect

Start with a primary care clinician or a urologist, not a peptide menu. The AUA guideline sets out the evaluation (AUA 2018):

1. History and examination, covering medical, sexual and psychosocial factors, medications, and the relationship; a validated questionnaire scores severity.
2. A morning total testosterone level in every man with ED, repeated if low. TRAVERSE required two fasting levels under 300 ng/dL plus symptoms before treating (Lincoff 2023).
3. Cardiovascular and metabolic basics: blood pressure, and for many men fasting glucose or HbA1c and fasting lipids, because ED is a risk marker.
4. Specialized testing, such as penile ultrasound, for selected men.
5. A treatment discussion that covers PDE5 inhibitors, devices, urethral and injected alprostadil, implants and, where deficient, testosterone.

Where a peptide fits: after that evaluation, a man with normal blood pressure who has failed a properly used PDE5 inhibitor can reasonably ask about off-label PT-141, from a prescriber who names the pharmacy and checks his blood pressure. Red flags are the opposite of this list: no labs, no blood pressure, a 'stack' in the cart, and kisspeptin or melanotan offered at all.

Cost

Figures are from our cost guide. Compounded peptides are cash-pay.

Bottom line

For erectile dysfunction, the honest ranking puts two non-peptides first: PDE5 inhibitors, which work for most men and cost little, and testosterone, which helps desire in men whose levels are truly low. Before either, ED deserves a cardiovascular check, because it often signals vascular disease years ahead.

Among peptides, PT-141 is the only one a licensed pharmacy can legally dispense, and its male evidence is a set of 2004 laboratory studies that FDA did not find convincing, with a blood pressure problem attached. Kisspeptin is promising research with no legal product. Oxytocin did not change erections in the studies that exist. Melanotan II should not be used at all, and the stacks combine these uncertainties without a single trial.

Frequently asked questions

+−Can PT-141 be used to treat erectile dysfunction?

It has never been approved for it. In 2004 laboratory studies, injected PT-141 at 4 and 6 mg produced measurable erections in men who responded poorly to sildenafil, but no phase 3 trial followed: in 2007 FDA questioned the efficacy results and named blood pressure increases as its greatest safety concern. The Vyleesi label says it is not indicated in men. Prescribing it for ED is off-label, usually at doses below the ones that worked, and it should not be used by men with uncontrolled high blood pressure or heart disease.

+−What is the best peptide for libido in men?

No peptide is approved for low libido in men. The two with human data are PT-141, studied for erections rather than desire, and kisspeptin, which raised measures of sexual desire and tumescence during one intravenous infusion in 32 men with low desire but cannot legally be compounded. If testosterone is confirmed low, testosterone therapy has the best evidence for desire: it improved desire and sexual activity in two large placebo-controlled trials.

+−Can erectile dysfunction be caused by low testosterone?

Sometimes, but less often than people think. Low testosterone mainly lowers desire; erections depend mostly on blood vessels and nerves. In the TRAVERSE sexual-function study of 1,161 men with confirmed low testosterone, two years of treatment improved desire and sexual activity but not erectile function. The urology guideline still recommends a morning testosterone test for every man with ED, and in men who are deficient, PDE5 pills may work better when testosterone is also treated.

+−Do PDE5 inhibitors work better than peptides for erectile dysfunction?

On the evidence, by a wide margin. In the pivotal sildenafil trial, 69% of intercourse attempts succeeded on the drug versus 22% on placebo, in hundreds of men followed for months, and PDE5 inhibitors are generic. No peptide has a single trial of men using it at home for ED that is not compromised. The usual reason pills fail is the wrong dose or wrong use, which a clinician can fix before anything experimental is considered.

+−What are ED injections, and are they peptides?

ED injections are medicines injected directly into the side of the penis, usually alprostadil alone or in a compounded mixture with other vasodilators. They are not peptides, they work within minutes regardless of desire, and the urology guideline lists them as a standard option, taught with an in-office test dose. They are a different thing from PT-141, which is injected under the skin of the belly and acts in the brain.

+−What is melanotan peptide used for?

Melanotan II was developed in the 1990s as a sunless tanning agent and produced erections in two small studies of 10 men each, which led to PT-141. It was never approved for anything. It is sold illegally for tanning and sex, case reports describe priapism needing surgery and melanomas arising in moles during use, and no US pharmacy may compound it as of October 2026.

+−Is there a peptide that raises testosterone?

Kisspeptin raises LH and testosterone for hours after a single dose in men with a working pituitary, but repeated or continuous dosing blunts the effect, it has never been tested as a treatment for low testosterone, and FDA's compounding committee voted 0 to 11 against it in 2024. The approved options for confirmed low testosterone are testosterone itself or, when fertility matters, hCG.

+−Are peptides for sexual arousal safe to buy online?

Not from a website selling vials for research. FDA's August 2026 warning letters named PT-141 among the products five online vendors sold illegally, and research vials have no label, pharmacist or verified potency. Kisspeptin and melanotan II have no legal source at all. The only libido peptide a licensed US pharmacy can dispense is bremelanotide, on a prescription, after a blood pressure check.

Sources

1. GuidelineBurnett AL et al. Erectile dysfunction: AUA guideline. J Urol 2018;200:633-41. (2018)
2. StudyGoldstein I et al. Oral sildenafil in the treatment of erectile dysfunction. Sildenafil Study Group. N Engl J Med 1998;338:1397-404. (1998)
3. ReviewVlachopoulos CV et al. Prediction of cardiovascular events and all-cause mortality with erectile dysfunction: a systematic review and meta-analysis of cohort studies. Circ Cardiovasc Qual Outcomes 2013;6:99-109. (2013)
4. StudySnyder PJ et al. Effects of testosterone treatment in older men (the Testosterone Trials). N Engl J Med 2016;374:611-24. (2016)
5. StudyLincoff AM et al. Cardiovascular safety of testosterone-replacement therapy (TRAVERSE). N Engl J Med 2023;389:107-17. (2023)
6. StudyPencina KM et al. Effect of testosterone replacement therapy on sexual function and hypogonadal symptoms in men with hypogonadism (TRAVERSE Sexual Function Study). J Clin Endocrinol Metab 2024;109:569-80. (2024)
7. LabelCosette Pharmaceuticals. VYLEESI (bremelanotide injection) prescribing information, revised March 2024. DailyMed. (2024)
8. StudyRosen RC et al. Evaluation of the safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141, a melanocortin receptor agonist, in healthy male subjects and in patients with an inadequate response to Viagra. Int J Impot Res 2004;16:135-42. (2004)
9. NewsKing Pharmaceuticals and Palatin Technologies. King Pharmaceuticals, Inc. and Palatin Technologies delay immediate plans for phase 3 clinical program with bremelanotide for erectile dysfunction (FDA questioned the efficacy results and cited blood pressure increases as its greatest safety concern). Press release via BioSpace, August 30, 2007. (2007)
10. NewsClarke H. Phase 2 study launches of bremelanotide plus a PDE5 inhibitor for erectile dysfunction. Urology Times, June 20, 2024. (2024)
11. StudyMills EG et al. Effects of kisspeptin on sexual brain processing and penile tumescence in men with hypoactive sexual desire disorder: a randomized clinical trial. JAMA Netw Open 2023;6:e2254313. (2023)
12. StudyBehnia B et al. Differential effects of intranasal oxytocin on sexual experiences and partner interactions in couples. Horm Behav 2014;65:308-18. (2014)
13. StudyWessells H et al. Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction. Urology 2000;56:641-6. (2000)
14. StudyMallory CW, Lopategui DM, Cordon BH. Melanotan tanning injection: a rare cause of priapism. Sex Med 2021;9:100298. (2021)
15. ReviewHabbema L, Halk AB, Neumann M, Bergman W. Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review. Int J Dermatol 2017;56:975-80. (2017)