A man who had used a tanning product for more than six years arrived at an emergency department with a painful erection that had lasted 30 hours.[9] He reported previous brief erections after use, but no earlier priapism—the medical term for a prolonged erection unrelated to sexual stimulation.[9] This time, after a reported Melanotan II injection, the episode required hospital treatment and was followed by persistent problems.[9]
The case, published by Chase Mallory, Diana Lopategui and Billy Cordon in 2021, challenges a familiar reassurance: “I have used it before without anything serious happening.”[9] It also requires careful interpretation. One case can document a serious event without establishing how often it occurs or proving every proposed explanation for it.
A tanning effect is only one biological effect
Melanotan II is a synthetic melanocortin analogue, a molecule designed to resemble a natural signaling hormone.[9] The case-report authors explain that melanocortin activity can stimulate skin pigmentation and that Melanotan II also acts at receptors involved in sexual arousal and erections.[9] The visible change sought by a user is therefore only part of its biological activity.
It would be misleading to dismiss tanning as an entirely imaginary effect. The authors describe published pigmentation findings, although their own report is a clinical case, not a controlled tanning trial.[9] It provides no dependable estimate of cosmetic benefit for a particular product, and a pigmentation effect cannot establish that continued use is safe.
Names also matter. The paper discusses Melanotan I, Melanotan II and bremelanotide as distinct melanocortin-related agents.[9] A study of one should not silently become evidence for another. Likewise, references to an approved medicine in this broader field would require checking the exact molecule, formulation and indication; they cannot be used as a shortcut to validate a research vial labeled Melanotan II.
What the 2021 case actually documented
The patient was 55 and reported injecting a product identified as Melanotan II beneath the skin before the prolonged erection began.[9] The authors recorded no preceding trauma, sexual stimulation or concurrent use of another drug.[9] These details help describe the clinical circumstances, but the account is not a controlled experiment establishing the contents and effects of every product sold under that name.
The diagnosis was ischemic priapism, the low-flow form of the condition, which the authors describe as a medical emergency capable of progressing to tissue fibrosis and erectile dysfunction.[9] Initial treatment did not resolve the episode, and surgery was required.[9] At the 15-week follow-up, the patient reported new erectile dysfunction, and examination found fibrosis, or tissue scarring.[9]
His earlier experience was not entirely symptom-free: the case history records severe nausea and short-lived erections with previous use.[9] Nevertheless, he reported no previous priapism.[9] That distinction is more useful than saying either that he had always tolerated it perfectly or that the later emergency was inevitable.
A severe, prolonged, painful erection requires urgent medical care. The report defines priapism as an erection lasting longer than four hours and describes the ischemic form as an emergency.[9] This is a reason to seek emergency assessment, not an invitation to attempt self-treatment or wait for a past pattern to repeat.
A serious signal does not supply an event rate
A case report gives clinicians a detailed observation to investigate. It does not provide a denominator—the number of exposed people needed to calculate how frequently an event occurs. Although “rare” appears in this paper's title, the report cannot establish a reliable incidence of priapism among Melanotan II users.[9]
| Observation or source | What it tells the reader | What it cannot establish |
|---|---|---|
| Pigmentation effects discussed in the paper.[9] | ||
| There is a biological basis for tanning interest. | A safe cosmetic benefit for an unspecified product. | |
| Priapism followed reported Melanotan II use.[9] | ||
| A serious temporal association was documented. | A population event rate or certainty about every causal factor. | |
| No prior priapism despite years of reported use.[9] | ||
| Earlier experience differed from this episode. | Protection from a later serious event. | |
| FDA summarizes several serious case reports.[1] | ||
| Multiple reported outcomes warrant attention. | Proof that Melanotan II caused each outcome. |
The authors proposed that prolonged drug activity might have contributed to the patient's course, but presented that explanation as a suspicion.[9] It should remain a hypothesis, not become a measured duration of action or an established mechanism. The article reports no funding and no declared conflicts of interest; those disclosures are useful context, but do not change the limits of a single case.[9]
Reading the other reported harms without exaggeration
FDA's April 2026 safety summary names published reports involving melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism in its Melanotan II entry.[1] It also identifies possible immune-response risks for certain routes because of aggregation or related impurities.[1] This is a set of safety concerns, not a table of proven causal effects or their frequency.
The melanoma reference deserves particular precision. FDA's listing says case reports discuss melanoma; it does not establish that Melanotan II causes melanoma.[1] The 2021 priapism report is not a tumor-causation study and cannot settle that question either.[9] Avoiding a blanket cancer claim preserves the distinction between a concerning report and demonstrated causation.
The same restraint works in the other direction. A report's inability to prove causation is not evidence that a product is harmless. In the supplied FDA page, Melanotan II sits among withdrawn nominations; that administrative placement does not resolve the safety concerns described alongside it.[1]
Why a research label cannot answer the human-use question
The case authors explicitly raise uncertainty about the purity and amounts supplied in internet products.[9] A chemical name, a purity figure or “research use only” wording alone cannot establish full identity, sterility, clinical safety or exposure appropriate to a particular route.[1][2][9] Reconstitution does not supply those missing assurances.
FDA explains that injectable products can bypass defenses against toxins and microorganisms and pose serious harm risks.[2] Its June 2026 warning letter concerned other products, so it is not evidence that a particular Melanotan II vial was contaminated. It illustrates why research labeling does not neutralize human-use concerns.[2]
Research materials should not be consumed or self-administered. A visible tanning effect and an uneventful earlier exposure answer much narrower questions than whether a particular preparation is suitable for human use. The documented priapism case makes that difference concrete, while leaving frequency, product equivalence and many causal questions unresolved.[1][2][9]