What is the difference between Melanotan II and PT-141?

PT-141 (bremelanotide, FDA-approved as Vyleesi) was derived directly from Melanotan II. Researchers found that removing the N-terminal acetyl group and a specific amino acid from MT-II produced a molecule that retained the MC4R sexual arousal effect while substantially reducing the tanning effect from MC1R activation. The result is PT-141, which is now FDA-approved for hypoactive sexual desire disorder in premenopausal women. MT-II is the original non-selective compound that activates all five melanocortin receptor subtypes (MC1R through MC5R), producing stronger tanning alongside its sexual effects.

Will I definitely get nausea from Melanotan II?

At doses above 0.5 mg, nausea is very common, affecting the majority of users. It typically occurs 30 to 60 minutes after injection and lasts 1 to 2 hours. At very low starting doses (0.1 to 0.25 mg), nausea is milder and many patients tolerate it. Titrating slowly upward allows the body to adapt. The nausea is caused by MC4R activation in the brain, the same receptor that produces the sexual effect, so the two are linked. Men sometimes take an OTC antiemetic 30 minutes before dosing; discuss this approach with your prescriber.

Does Melanotan II cause permanent skin darkening?

The tanning effect from MT-II is not permanent in the conventional sense, but it is more persistent than UV-induced tanning. MC1R activation drives melanocyte stimulation and melanin production independently of UV exposure. The effect accumulates with repeated dosing and fades more slowly than sun-induced tanning, taking weeks to months to fade after stopping. Existing moles and nevi can darken. Any new or changing moles during or after a course warrant dermatology evaluation.

Can Melanotan II raise blood pressure?

Yes, transiently. The Phase 2 erectile dysfunction studies documented blood pressure elevations in some participants, which is why a cardiovascular screen is part of the intake process. The effect is typically mild and transient. Patients with hypertension, cardiovascular disease, or those taking blood pressure medications should have specific prescriber review before using MT-II.

Is the tanning from Melanotan II safe from a skin cancer standpoint?

The tanning effect is melanin-based, driven by MC1R activation of melanocytes, which is the same mechanism as UV-induced tanning. Whether pharmacologically induced melanin reduces UV skin damage the way UV-induced tanning does, or whether the pattern of MC1R activation is identical to sun exposure, has not been thoroughly studied. What is documented is that existing moles can darken and that new moles in the context of any tanning agent require monitoring. Regular skin checks with a dermatologist are recommended during and after a course.

Non-Selective Melanocortin Agonist · MC1R Tanning · MC4R Sexual Response · Protocol Guide

Melanotan II: The Honest MT2 Peptide Guide

Melanotan II (MT-II) is a synthetic cyclic analog of alpha-MSH that activates melanocortin receptors responsible for both UV-independent tanning and sexual arousal. It has real human trial data going back to 1991. It also has a nausea rate that is nearly universal at standard doses and a side-effect profile that demands careful titration. This guide covers both.

FDA Status: No approval; related compound PT-141 FDA-approved
Pharmacy: Optimal Balance Pharmacy (503A licensed)
Medical Service: RxPepsDirect, physician-supervised
Access: 28 U.S. States

Our promise: Melanotan II has more human trial data than most peptides in this class, including published Phase 1 and Phase 2 studies going back to the 1990s. It also has real side effects: nausea affects nearly all patients at doses above 0.5 mg, pigmentation changes are expected, and blood pressure effects have been documented. We state all of that clearly rather than burying it.

Medically reviewed by Dr. Jonathan Snipes, MD. Last reviewed June 17, 2026.

On this page

Section 01

What Melanotan II Actually Is

Melanotan II (MT-II) is a synthetic cyclic heptapeptide developed at the University of Arizona in the late 1980s as a more potent and stable analog of alpha-melanocyte-stimulating hormone (alpha-MSH), a naturally occurring peptide that regulates pigmentation, appetite, and sexual function through the melanocortin receptor system. The research team led by Victor Hruby designed MT-II specifically to have higher receptor affinity and longer half-life than the natural peptide.

MT-II activates all five melanocortin receptor subtypes (MC1R through MC5R) non-selectively. Two of those targets explain why it is prescribed today. MC1R, found on melanocytes in the skin, drives melanin production and produces the tanning effect. MC4R, found in the hypothalamus, mediates sexual arousal, erection, and female genital response. These two effects are physiologically linked through the same receptor agonism, which is why they are difficult to separate.

The FDA-approved sexual health compound PT-141 (bremelanotide, marketed as Vyleesi) was derived directly from MT-II. Researchers found that modifying the MT-II structure reduced the tanning effect while preserving the sexual response effect. PT-141 is now the only FDA-approved on-demand treatment for hypoactive sexual desire disorder (HSDD) in premenopausal women. MT-II is the broader parent compound that remains available through 503A compounding.

1991

Year of the first human MT-II tanning trial (Levine, JAMA)

MC1R + MC4R

Primary receptors driving tanning and sexual response

5 mg

Total in a 5 mL vial at OBP's 1 mg/mL concentration

503A

Pathway for U.S. compounded access under physician prescription

Section 02

Who It Is Actually For

MT-II serves a dual population because its two primary effects (tanning and sexual response) are inseparable at the receptor level. Most patients use it for one or both effects simultaneously.

Profile	Primary Use	Evidence Basis	Fit
Men with erectile dysfunction, psychogenic origin	On-demand pro-erectile support via MC4R	Wessells 1998: double-blind crossover, significant erectile response vs placebo in men with psychogenic ED.	Phase 2 RCT Support
Women with low sexual desire / HSDD	Increased arousal and desire via MC4R	Closely related compound PT-141 is FDA-approved for female HSDD. MT-II MC4R mechanism is identical; direct MT-II trials in women are limited.	Mechanistic, PT-141 Validated
Tanning without UV exposure	Skin darkening via MC1R on melanocytes	Levine 1991 (JAMA): visible tanning in 9/10 subjects without UV exposure. Long history of clinical study.	Phase 2 Evidence
Combined tanning and sexual response goal	Both effects together	Both effects are mediated by MT-II; they occur together. Titrate for tolerance.	Documented Both Effects
Patients with history of melanoma or unusual moles	Any cosmetic or sexual use	MC1R activation stimulates melanocytes. Melanoma history warrants dermatology clearance.	Dermatology Clearance Required
Patients with uncontrolled hypertension or cardiovascular disease	Any use	BP elevations documented in ED trials. Cardiovascular screen mandatory.	Cardiovascular Screen Required

Profile

Men with erectile dysfunction, psychogenic origin

Primary Use

On-demand pro-erectile support via MC4R

Evidence Basis

Wessells 1998: double-blind crossover, significant erectile response vs placebo in men with psychogenic ED.

Fit

Phase 2 RCT Support

Profile

Women with low sexual desire / HSDD

Primary Use

Increased arousal and desire via MC4R

Evidence Basis

Closely related compound PT-141 is FDA-approved for female HSDD. MT-II MC4R mechanism is identical; direct MT-II trials in women are limited.

Fit

Mechanistic, PT-141 Validated

Profile

Tanning without UV exposure

Primary Use

Skin darkening via MC1R on melanocytes

Evidence Basis

Levine 1991 (JAMA): visible tanning in 9/10 subjects without UV exposure. Long history of clinical study.

Fit

Phase 2 Evidence

Profile

Combined tanning and sexual response goal

Primary Use

Both effects together

Evidence Basis

Both effects are mediated by MT-II; they occur together. Titrate for tolerance.

Fit

Documented Both Effects

Profile

Patients with history of melanoma or unusual moles

Primary Use

Any cosmetic or sexual use

Evidence Basis

MC1R activation stimulates melanocytes. Melanoma history warrants dermatology clearance.

Fit

Dermatology Clearance Required

Profile

Patients with uncontrolled hypertension or cardiovascular disease

Primary Use

Any use

Evidence Basis

BP elevations documented in ED trials. Cardiovascular screen mandatory.

Fit

Cardiovascular Screen Required

Section 03

How Melanotan II Works

MT-II works through two principal mechanisms operating in parallel. Understanding both helps set accurate expectations for what will happen and when.

MC1R: The Tanning Pathway

MT-II binds MC1R on skin melanocytes, activating a cAMP cascade that upregulates eumelanin production. Eumelanin is the brown-black pigment that determines baseline skin tone and provides UV protection. The effect occurs without UV exposure but can be amplified by sun exposure. Pigmentation accumulates over multiple doses and fades slowly after stopping.

MC4R: The Sexual Arousal Pathway

MT-II crosses the blood-brain barrier and activates MC4R in the paraventricular nucleus of the hypothalamus. This triggers downstream dopamine and oxytocin release, producing penile erection in men and genital engorgement plus increased desire in women. The effect is centrally mediated, meaning it starts in the brain and works with (not against) natural arousal.

Why Nausea Happens

MC4R is also expressed in the dorsal vagal complex, the brain region that controls nausea and vomiting. MT-II activates it there as well as in the hypothalamus. The nausea and the sexual effect share the same receptor. You cannot get one without the risk of the other; dose titration is the only tool to find the window where sexual response is present and nausea is tolerable.

Blood Pressure Effect

Melanocortin receptor activation affects vascular tone. In the clinical trials, blood pressure elevations were documented, particularly in the hour following injection. The mechanism involves MC4R-driven autonomic effects on vascular resistance. The elevation is typically transient and mild in normotensive patients but warrants monitoring.

Section 04

What the Evidence Shows

MT-II has one of the longer human trial histories of any peptide in this space. The evidence for both tanning and erectile response is real and from controlled studies. MT-II was ultimately not developed into an FDA-approved product; its successor PT-141 carried that program forward. Here is the actual record.

Study	Design	Key Finding	Strength
Levine 1991 (JAMA) [1]	Phase 1, 10 subjects, subcutaneous MT-II, 5 days without UV exposure	9 of 10 subjects developed visible, measurable tanning (spectrophotometry). First proof that melanocortin agonism can produce tanning without UV.	Phase 1, Landmark
Wessells 1998 (J Urol) [2]	Double-blind, crossover RCT, men with psychogenic ED. 0.025 mg/kg subcutaneous, single dose.	Significant erectile response (rigidity and duration) vs placebo. Penile tumescence measured via RigiScan. Nausea in 8/19 subjects at this dose.	Phase 2 RCT, Positive
Hadley 2006 (Peptides) [5]	Review: 15+ years of melanocortin peptide research and clinical development	Summarizes the full MT-II and then PT-141 development arc. Tanning effect is robust and dose-dependent. Sexual effect validated; nausea is the dose-limiting side effect.	Comprehensive Review
PT-141 / bremelanotide program (Diamond 2006, etc.) [4]	Phase 2 RCTs in women with arousal disorder, culminating in FDA approval (Vyleesi) in 2019	Validates the MC4R sexual arousal mechanism in women. PT-141 derived directly from MT-II. FDA approval confirms the target.	FDA-Validated Mechanism

Study

Levine 1991 (JAMA) [1]

Design

Phase 1, 10 subjects, subcutaneous MT-II, 5 days without UV exposure

Key Finding

9 of 10 subjects developed visible, measurable tanning (spectrophotometry). First proof that melanocortin agonism can produce tanning without UV.

Strength

Phase 1, Landmark

Study

Wessells 1998 (J Urol) [2]

Design

Double-blind, crossover RCT, men with psychogenic ED. 0.025 mg/kg subcutaneous, single dose.

Key Finding

Significant erectile response (rigidity and duration) vs placebo. Penile tumescence measured via RigiScan. Nausea in 8/19 subjects at this dose.

Strength

Phase 2 RCT, Positive

Study

Hadley 2006 (Peptides) [5]

Design

Review: 15+ years of melanocortin peptide research and clinical development

Key Finding

Summarizes the full MT-II and then PT-141 development arc. Tanning effect is robust and dose-dependent. Sexual effect validated; nausea is the dose-limiting side effect.

Strength

Comprehensive Review

Study

PT-141 / bremelanotide program (Diamond 2006, etc.) [4]

Design

Phase 2 RCTs in women with arousal disorder, culminating in FDA approval (Vyleesi) in 2019

Key Finding

Validates the MC4R sexual arousal mechanism in women. PT-141 derived directly from MT-II. FDA approval confirms the target.

Strength

FDA-Validated Mechanism

Section 05

Realistic Expectations

MT-II produces noticeable effects relatively quickly compared to most compounded peptides, because it acts on receptors that produce acute responses. The timeline below reflects typical patient experience during a tanning course with concurrent sexual response use.

Dose 1

Acute Response Test

Within 30 to 60 minutes: possible nausea (especially if you started above 0.25 mg), possible flushing and warmth, and in men, possible spontaneous erection. These responses confirm the peptide is active. The goal at dose one is to establish your tolerance floor.

Wk 1-2

Titration Window

Daily or every-other-day low doses (0.1 to 0.25 mg) build tolerance to the acute nausea while beginning melanin accumulation. Most patients find that nausea diminishes significantly by weeks one to two at a stable dose.

Wk 2-4

Pigmentation Develops

Visible tanning becomes apparent in this window, typically starting in areas with existing pigmentation (nipples, genitals, freckles) and spreading to general skin tone. Sun exposure during this period amplifies the effect. Moles and existing dark spots will also darken.

Ongoing

Maintenance Dosing

Once target pigmentation is reached (typically 4 to 6 weeks), dose frequency can be reduced to once or twice weekly to maintain the effect. Stopping MT-II allows pigmentation to gradually fade over weeks to months.

Section 06

Dosing Protocol

MT-II dosing is managed in two phases: a loading phase to build pigmentation and establish dose tolerance, and a maintenance phase to sustain the effect. The sexual response use is on-demand: a dose taken 45 to 90 minutes before activity. The tanning use is cumulative with regular dosing. OBP supplies MT-II at 1 mg/mL in a 5 mL vial, giving 5 mg total.

Phase	Dose	Frequency	Notes
Test dose (day 1)	0.1 to 0.25 mg (10 to 25 units on a 1 mL syringe)	Single dose, late afternoon or evening	Establishes individual tolerance. Expect possible nausea and flushing.
Titration loading	0.25 to 0.5 mg, increasing only if prior dose was tolerated	Daily or every other day	Build pigmentation and tolerance over 2 to 4 weeks.
RxPepsDirect Standard (tanning + maintenance)	0.25 to 0.5 mg at established tolerance	2 to 3 times weekly for maintenance once target achieved	Physician sets dose based on individual tolerance and goal.
On-demand sexual response use	Individual effective dose (typically 0.5 to 1 mg)	Single dose 45 to 90 minutes before activity	Use the dose established during titration. Avoid dosing into situations with prolonged nausea.

Phase

Test dose (day 1)

Dose

0.1 to 0.25 mg (10 to 25 units on a 1 mL syringe)

Frequency

Single dose, late afternoon or evening

Notes

Establishes individual tolerance. Expect possible nausea and flushing.

Phase

Titration loading

Dose

0.25 to 0.5 mg, increasing only if prior dose was tolerated

Frequency

Daily or every other day

Notes

Build pigmentation and tolerance over 2 to 4 weeks.

Phase

RxPepsDirect Standard (tanning + maintenance)

Dose

0.25 to 0.5 mg at established tolerance

Frequency

2 to 3 times weekly for maintenance once target achieved

Notes

Physician sets dose based on individual tolerance and goal.

Phase

On-demand sexual response use

Dose

Individual effective dose (typically 0.5 to 1 mg)

Frequency

Single dose 45 to 90 minutes before activity

Notes

Use the dose established during titration. Avoid dosing into situations with prolonged nausea.

Evening or late-afternoon dosing is preferred by most patients because nausea peaks 1 to 2 hours after injection, making it easier to manage during sleep or low-activity periods. Injections are subcutaneous into abdominal fat with a standard insulin syringe. Rotate sites to avoid local pigmentation clustering.

Section 07

Ready to Inject

Reconstitution steps required

503A

Licensed pharmacy (Optimal Balance), physician-supervised

Overnight

FedEx shipping in a reusable cooled travel case

Section 08

Safety and Side Effects

MT-II has a well-documented side effect profile from its clinical trial program. The effects below are real, dose-dependent, and manageable with proper titration. None of them are hidden risks; they were reported in the published trials.

Side Effect	Frequency / Severity	Management
Nausea and vomiting	Very common above 0.5 mg. Mild to severe. Onset 30 to 60 min, duration 1 to 2 hours.	Titrate slowly from 0.1 to 0.25 mg. Evening dosing. OTC antiemetic (discuss with prescriber). Do not force through severe nausea.
Flushing and warmth	Common at any dose. Usually mild.	Expected, transient. Usually diminishes with repeated dosing.
Spontaneous erection (men)	Common, dose-dependent. Can be prolonged.	Reduces with dose titration. Priapism (prolonged erection > 4 hours) requires emergency care.
Skin pigmentation and mole darkening	Expected with regular dosing. Cumulative.	Existing moles can darken. New or changing moles during use require dermatology evaluation.
Blood pressure elevation	Documented in ED trials. Typically transient, 1 to 2 hours post-dose.	Baseline BP measurement before starting. Avoid in uncontrolled hypertension. Monitor BP during titration.
Melanoma history or atypical moles	MC1R agonism stimulates melanocytes	Dermatology clearance required before starting. Not appropriate for active melanoma.
Pregnancy / lactation	No safety data	Avoid.

Side Effect

Nausea and vomiting

Frequency / Severity

Very common above 0.5 mg. Mild to severe. Onset 30 to 60 min, duration 1 to 2 hours.

Management

Titrate slowly from 0.1 to 0.25 mg. Evening dosing. OTC antiemetic (discuss with prescriber). Do not force through severe nausea.

Side Effect

Flushing and warmth

Frequency / Severity

Common at any dose. Usually mild.

Management

Expected, transient. Usually diminishes with repeated dosing.

Side Effect

Spontaneous erection (men)

Frequency / Severity

Common, dose-dependent. Can be prolonged.

Management

Reduces with dose titration. Priapism (prolonged erection > 4 hours) requires emergency care.

Side Effect

Skin pigmentation and mole darkening

Frequency / Severity

Expected with regular dosing. Cumulative.

Management

Existing moles can darken. New or changing moles during use require dermatology evaluation.

Side Effect

Blood pressure elevation

Frequency / Severity

Documented in ED trials. Typically transient, 1 to 2 hours post-dose.

Management

Baseline BP measurement before starting. Avoid in uncontrolled hypertension. Monitor BP during titration.

Side Effect

Melanoma history or atypical moles

Frequency / Severity

MC1R agonism stimulates melanocytes

Management

Dermatology clearance required before starting. Not appropriate for active melanoma.

Side Effect

Pregnancy / lactation

Frequency / Severity

No safety data

Management

Avoid.

Section 09

Stacking

Pairs Well With

Oxytocin
Bonding and intimacy peptide via a completely different pathway (oxytocin receptor, not melanocortin). Oxytocin amplifies the emotional and relational dimension of sexual experience. No known pharmacological interaction with MT-II. Separate timing.
Kisspeptin
Upstream reproductive axis activator (KISS1/GPR54). Works through a different central pathway. Some longevity and desire use cases overlap. No known interaction with melanocortin agonism.

Avoid or Combine With Caution

PT-141 (bremelanotide)
MT-II and PT-141 are related melanocortin agonists targeting the same MC4R pathway. Combining them stacks receptor activation with no documented benefit and amplified nausea and blood pressure risk. Use one or the other, not both.
Antihypertensive medications
MT-II can produce transient BP elevations. Patients on antihypertensives should have their prescriber review the interaction before starting, as BP effects could be unpredictable in both directions.
Pregnancy
No safety data. Avoid.

Section 10

Pricing

Pharmacy: Medication

$80 per 5 mg vial. Compounded and shipped by Optimal Balance Pharmacy, a 503A licensed compounding pharmacy. Pre-reconstituted at 1 mg/mL, FedEx overnight. 90-day Beyond Use Date.

Medical Service: Physician Consultation

$39 medical visit fee. Intake consultation including cardiovascular screen, skin history review, protocol design, titration guidance, and prescription writing. Billed by RxPepsDirect for the medical service only.

Section 11

Legal Access in 28 States

503A Licensed Pharmacy

Optimal Balance Pharmacy, U.S. licensed

Physician Prescription Required

Compounded medication, Rx only

Phase 2 Evidence, No FDA Approval

Related compound PT-141 is FDA-approved

Off-Label, Legal Practice

Standard and legal in U.S. medicine

Melanotan II is not FDA-approved. Its related compound PT-141 (bremelanotide) received FDA approval in 2019 for female HSDD, validating the MC4R sexual arousal pathway. MT-II is available in the United States through 503A patient-specific compounding under a physician prescription. RxPepsDirect prescribers serve patients in 28 states.

Section 12

Community Q&A

What is the difference between MT-II and PT-141?

PT-141 (bremelanotide, Vyleesi) was derived from MT-II by modifying the structure to reduce tanning (less MC1R activation) while retaining the sexual arousal effect (MC4R activation). PT-141 is FDA-approved for female HSDD. MT-II is the original non-selective compound with stronger tanning alongside the sexual response. They are related but distinct; do not combine them.

Will the nausea get better over time?

Yes, for most patients. Nausea is typically worst at the first few doses and diminishes significantly as the body adapts to MC4R stimulation. The key is starting at a very low dose (0.1 to 0.25 mg) and titrating up only after each dose level is tolerated. Pushing to high doses early causes severe nausea and does not accelerate adaptation.

Does the tanning fade when I stop?

Yes, gradually. MT-II-induced pigmentation fades more slowly than UV-induced tanning because it directly stimulates melanin production rather than triggering a reactive tanning response. Expect several weeks to months for the full effect to fade after stopping. Maintenance dosing at reduced frequency can sustain the pigmentation.

Is MT-II safe for someone with freckles or fair skin?

MT-II strongly activates MC1R, which drives melanin production in all melanocytes including those responsible for freckles. Freckles typically darken prominently. Fair-skinned patients often see results more dramatically. The skin cancer question is that any mole changes require dermatology monitoring; the melanin produced is eumelanin, the protective type, but stimulating melanocytes in someone with a personal or family history of melanoma requires dermatology clearance first.

How does it interact with blood pressure medications?

MT-II produces transient blood pressure elevations in some patients. If you take antihypertensive medications, your prescriber needs to review the combination before you start. The interaction could go either way depending on your medication class and current BP control. This is part of the intake cardiovascular screen.

Section 13

The RxPepsDirect Model

Pharmacy: Optimal Balance, 503A Licensed

Optimal Balance Pharmacy compounds your MT-II under a patient-specific prescription, USP <797> sterile standards, and federal 503A oversight. Pre-reconstituted at 1 mg/mL.

Medical Service: RxPepsDirect Physicians

A licensed physician conducts a cardiovascular screen, reviews your skin and mole history, sets your starting titration dose, and writes your prescription. RxPepsDirect bills the $39 medical visit fee for this service.

Transparent Safety Communication

This guide covers nausea, priapism risk, blood pressure elevation, mole darkening, and the PT-141 distinction honestly. We do not hide the side-effect profile to make a sale.

Legal Access in 28 States

Every shipment is a compounded prescription medication filled by a 503A licensed pharmacy under a physician prescription.

References

Levine N, Sheftel SN, Eytan T, et al. Induction of skin tanning by subcutaneous administration of a potent synthetic melanotropin. JAMA. 1991. PMID: 1942436
Wessells H, Fuciarelli K, Hansen J, et al. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo-controlled crossover study. J Urol. 1998. PMID: 9763085
Shadiack AM, Sharma SD, Earle DC, et al. Melanocortins in the treatment of male and female sexual dysfunction. Curr Top Med Chem. 2007. PMID: 17584149
Diamond LE, Earle DC, Heiman JR, et al. An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. J Sex Med. 2006. PMID: 16681470
Hadley ME, Dorr RT. Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides. 2006. PMID: 16412524

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