Melanotan II — Reconstitution & Dosage Calculator

What Is Melanotan II?

Melanotan II (MT-2) is a synthetic cyclic heptapeptide analog of α-melanocyte-stimulating hormone (α-MSH), with the lactam-bridged structure Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂. It was developed at the University of Arizona in the early 1990s as part of a program to create superpotent, protease-resistant melanotropic agents — Hadley and Dorr (1998) recount the discovery of both Melanotan-I and -II as α-MSH analogs. The first-in-human pilot study, Dorr et al. (1996), reported dose-dependent melanotropic (tanning) activity at 0.01 mg/kg in three volunteers.

MT-2 is a non-selective agonist across the melanocortin receptor family (MC1R, MC3R, MC4R, MC5R). MC1R activation drives melanogenesis (its tanning effect), while MC4R activation influences sexual function and appetite. This broad receptor activity explains both its effects and its side-effect profile. Notably, the MC4R-selective successor bremelanotide (PT-141) — derived from the MT-2 lineage — is an FDA-approved drug; see PT-141 for that regulated compound. MT-2 itself is not approved and is used illegally as a tanning agent, a point central to its safety literature below.

Research Context

Evidence Level: The human evidence for MT-2 is dominated by early pharmacology studies and, critically, case reports of harm from unregulated use. MT-2 is not an approved drug. Nothing here is a clinical recommendation, and the adverse-event record is a core part of the evidence.

Overview

The MT-2 literature falls into three uneven groups: early pharmacology and receptor-mapping studies from the 1990s–2000s, mechanistic melanocortin-receptor chemistry, and a growing body of adverse-event case reports documenting harm from internet-sourced product. Unlike research peptides with efficacy pipelines, MT-2’s most clinically relevant modern literature concerns safety signals from unregulated self-injection, not therapeutic development.

Melanogenesis and Tanning Pharmacology

The tanning effect is the best-documented action. Dorr et al. (1996) demonstrated dose-dependent melanotropic activity in the first human pilot, and preformulation work by Lan et al. (1995) characterized the peptide’s ionization (His pKa 6.54, Arg pKa 11.72) and partitioning while framing it as a candidate skin-cancer chemopreventive and tanning agent. The mechanism is MC1R activation on melanocytes, increasing eumelanin synthesis — the basis for the “tanning” it is marketed for.

Melanocortin Receptor Pharmacology and Mechanism

MT-2 has served as a key pharmacological tool for mapping melanocortin receptors. Haskell-Luevano et al. (2001) used MT-II and analogs in MC4R mutagenesis studies to identify ligand–receptor interaction determinants. More recent chemistry by Tomassi et al. (2022) replaced MT-II’s lactam bridge with xylene thioethers to create functionally selective receptor agonists — work that underscores that MT-2 itself is a potent but non-selective pan-melanocortin agonist, the pharmacological root of its off-target effects.

MC4R and Sexual Function

Because MC4R activation affects sexual arousal pathways, MT-2 produces erectogenic effects, and this observation drove development of a selective successor. Hedlund (2004) profiled early development of PT-141 (bremelanotide), a modified analog positioned for sexual dysfunction, and Dhillon and Keam (2020) documented bremelanotide’s first approval for hypoactive sexual desire disorder. MT-2 is the non-selective parent of this now-regulated, MC4R-selective drug — see PT-141.

Adverse Events from Unregulated Use (Safety-Critical)

This is the most important body of MT-2 literature. Multiple peer-reviewed case reports link unregulated MT-2 to serious harm:

• Priapism: Dreyer and Fritchie (2019) reported acute low-flow priapism after subcutaneous injection used illegally for tanning, requiring cavernosal aspiration.
• Renal infarction and rhabdomyolysis: Peters and Whittall (2021) described renal infarction, rhabdomyolysis, and renal failure associated with a non-selective melanocortin agonist obtained without regulation.
• Pigmented-lesion changes: Burian et al. (2020) systematically reviewed eruptive melanocytic nevi and found a substantial fraction linked to immunosuppression, chemotherapy, or melanotan — raising concern about melanoma and evolving moles.

Gilhooley et al. (2022) and an earlier warning by Evans-Brown et al. (2009) document widespread unregulated internet acquisition and self-injection, establishing that MT-2 has circulated in the general population as an unlicensed product for well over a decade.

Methodological Observations

The efficacy pharmacology rests on small, early human pilots and receptor-mapping chemistry, while the modern safety literature is built from individual case reports and case series — a study design that establishes association and hazard signals but not incidence rates. There is no large controlled safety trial of MT-2 in humans, because it was never developed to approval; the selective successor bremelanotide carries the regulated clinical dataset instead.

Research Gaps and Limitations

• Evidence level gap — No modern randomized controlled trials of MT-2; efficacy data are limited to 1990s pilots.
• Safety quantification gap — Serious harms (priapism, rhabdomyolysis, renal infarction, nevus changes) are documented in case reports without denominator data, so true incidence is unknown.
• Product-quality gap — Because supply is unregulated, purity, dose accuracy, and sterility of consumer MT-2 are not assured.
• Regulatory gap — MT-2 is not approved anywhere as a tanning agent; regulators have issued warnings against its sale and use.
• Melanoma surveillance gap — The interaction between MC1R stimulation and existing pigmented lesions is not well characterized in long-term human data.

Reconstitution Mathematics

Accurate reconstitution is critical for consistent dosing in any laboratory protocol. The interactive calculator on this page handles all the arithmetic — but understanding the underlying formula is useful for verification:

Concentration (mg/mL) = Vial Size (mg) ÷ BAC Water Added (mL)
Dose Volume (mL)      = Desired Dose (mg) ÷ Concentration (mg/mL)
Syringe Units (IU)    = Dose Volume (mL) × 100   [for U-100 insulin syringe]

Common laboratory reconstitution examples:

Use the interactive calculator on this page for any custom vial size, water volume, or dose.

Common Research Dosing Parameters

Reported in early pilot studies and community conventions. These are not clinical recommendations, and MT-2 is not approved for human use.

MT-2 doses are small relative to repair peptides. The following reflects the ranges described in the literature and community practice:

Key observations from the literature:

• The original human pilot used weight-based dosing (~0.01 mg/kg SC; Dorr et al., 1996)
• Nausea, facial flushing, spontaneous erections, and darkening of moles are among the most frequently reported effects
• Higher doses correlate with more frequent and severe adverse events in the case-report literature

Graduated Dosing Design from Reported Use

The following reflects loading-then-maintenance patterns described in the literature and community reports. It is not a clinical protocol, and the adverse-event record above applies at all doses.

Reconstitution assumption: 10 mg vial + 2 mL BAC water = 5 mg/mL concentration

*Example doses calculated for illustrative purposes based on common vial configurations.

Dose range sources:

• Weight-based pilot dosing (~0.01 mg/kg) from Dorr et al. (1996)
• Loading/maintenance pattern reflects community convention, not a controlled dose-finding trial
• Adverse-event context at higher doses from Peters and Whittall (2021) and Dreyer and Fritchie (2019)

Important notes:

• MT-2 is not approved for human use; these figures document reported practice, not endorsed dosing
• IU values assume a U-100 insulin syringe (1 IU = 0.01 mL)
• Any new or changing pigmented lesion during use warrants prompt dermatological evaluation

Stability & Storage

Bacteriostatic water (BAC water, 0.9% benzyl alcohol) is the standard diluent for reconstitution because benzyl alcohol acts as a preservative, extending the usable life of the reconstituted solution.

Reconstitution procedure (standard laboratory protocol):

1. Allow vial to reach room temperature (~15 minutes)
2. Wipe septum with 70% isopropyl alcohol
3. Draw desired BAC water volume into a sterile syringe
4. Insert needle at a 45° angle and inject slowly along the vial wall — do not inject directly onto the lyophilized cake
5. Gently swirl (do not shake or vortex) until fully dissolved
6. Label vial with date, concentration, and store per table above

Frequently Asked Questions

How many units do I draw for 500 mcg of Melanotan II?

It depends on your reconstitution ratio. With a 10 mg vial in 2 mL BAC water (5 mg/mL concentration), a 500 mcg dose = 10 units on a U-100 insulin syringe. With 1 mL BAC water (10 mg/mL), the same dose = 5 units. Use the calculator above — or the multi-peptide calculator — for your specific setup.

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

MT-2 is a non-selective melanocortin agonist (it activates MC1R for tanning and MC4R for sexual effects). PT-141 (bremelanotide) is a modified, MC4R-selective successor that was developed specifically for sexual dysfunction and is FDA-approved for that use. MT-2 is not approved.

What are the known side effects of Melanotan II?

The peer-reviewed literature documents nausea and facial flushing commonly, and — in case reports — priapism (Dreyer and Fritchie, 2019), rhabdomyolysis and renal infarction (Peters and Whittall, 2021), and darkening or eruption of moles with melanoma concern (Burian et al., 2020). Any changing pigmented lesion should be evaluated by a clinician.

Is Melanotan II legal or approved?

No. MT-2 is not approved as a tanning agent in any major jurisdiction, and regulators have warned against its sale. It circulates as an unlicensed, unregulated product (Evans-Brown et al., 2009), meaning purity and dose accuracy are not assured.

How long does reconstituted Melanotan II last in the refrigerator?

Reconstituted in bacteriostatic water and stored at 2–8 °C, MT-2 remains chemically stable for up to 28 days. Always use a fresh alcohol swab on the vial septum before each draw. If the solution becomes cloudy or discolored, discard it.

Why does Melanotan II cause spontaneous erections?

Because it non-selectively activates MC4R in addition to the MC1R receptor responsible for tanning. MC4R activation influences central sexual-arousal pathways — the same mechanism later isolated in the selective drug PT-141. This is an expected pharmacological effect, not a contaminant.

FOR RESEARCH PURPOSES ONLY. Not for human consumption. Not for veterinary use. Not a drug, food, or cosmetic.