PT-141 (Bremelanotide) Reconstitution Calculator

PT-141, or bremelanotide, is a synthetic melanocortin-receptor agonist that's FDA-approved under the brand Vyleesi for premenopausal women with hypoactive sexual desire disorder. What makes it distinctive is where it acts: instead of increasing blood flow the way Viagra and Cialis (PDE5 inhibitors) do, it switches on MC4R receptors in the brain to raise sexual desire itself. It's actually a refined relative of Melanotan 2 — developed to keep the sexual effects while dialing down the tanning — which is why it can still cause mild skin darkening.

It's sold as a lyophilized powder, commonly in 10 mg vials, so add bacteriostatic water down the vial wall, swirl gently, and don't shake. As a worked example, a 10 mg vial with about 2.85 mL of bacteriostatic water gives 3.5 mg/mL, so the 1.75 mg dose used in the approved Vyleesi product is 0.5 mL — 50 units on a U-100 insulin syringe. Off-label male protocols often start lower (community reports commonly begin around 0.5 mg), and reconstituted vials should be kept refrigerated.

The evidence isn't symmetrical. For women, PT-141 has the strongest footing — the Phase 3 RECONNECT trials led to FDA approval for premenopausal HSDD, so its use in women is on-label. For men it's used off-label: there's Phase 2 data suggesting it can help erectile dysfunction, including in men who don't respond to Viagra-type drugs, but the male program was never completed and it isn't FDA-approved for men. Because MC4R signaling drives desire in both sexes, it's used across both, just with very different levels of formal backing.

Subcutaneous injection is the route with the real evidence — it's how Vyleesi is delivered and how the trials were run. A nasal spray exists and is sometimes compounded, but intranasal PT-141 is investigational, and in men the nasal program was actually stopped over blood-pressure spikes; absorption is also less consistent than injection. Oral and pill forms are marketed too, but as a peptide it's poorly absorbed by mouth, so injection remains the reference route.

The most common side effect by far is nausea — around 40% of women in trials — along with flushing, headache, and injection-site reactions. The one that deserves respect is a transient rise in blood pressure after dosing, which is why the label rules it out for anyone with uncontrolled hypertension or cardiovascular disease, and repeated frequent dosing can cause patchy skin darkening. Two clarifications worth making: PT-141 does not raise testosterone — it works on brain desire pathways, not hormones — and because of the blood-pressure effect, combining it with other sexual-function drugs is something to run past a doctor rather than do casually.