PT-141 Dosage Calculator (Bremelanotide, Vyleesi)
Approved as Vyleesi for hypoactive sexual desire disorder — as a ready-to-use autoinjector, not as a powder.
Written by Kashif Khan, who builds and maintains this site and is not a clinician. Every figure links to its primary source.
FDA-approved as a solution, not as a powder
Bremelanotide was approved in 2019 as VYLEESI, a single-dose prefilled autoinjector containing 1.75 mg in 0.3 mL. There is no reconstitution step in the approved product. PT-141 sold as a lyophilised powder for you to mix is not the FDA-approved presentation. The label contraindicates it in uncontrolled hypertension and known cardiovascular disease.
Key facts
- Molecular weight
- 1,025.2 DaFree base. The drug substance is bremelanotide acetate, C50H68N14O10 with 1 to 2 acetate equivalents.
- Half-life
- About 2.7 hours after a subcutaneous dose (range 1.9–4.0), with a median Tmax of about 1 hour
- Also sold as
- bremelanotide, Vyleesi
How good is the evidence?
Approved with a defined dose and defined frequency limits: no more than one dose in 24 hours, and more than 8 doses per month is not recommended.
Pharmacokinetics, and why the timing instruction exists
The label instructs that the dose be taken at least 45 minutes before anticipated sexual activity, and the pharmacokinetics say why: median Tmax after a subcutaneous dose is about 1 hour (range 0.5 to 1.0), and the mean terminal half-life is about 2.7 hours, with a range of 1.9 to 4.0. Absolute bioavailability by the subcutaneous route is about 100%, and the mean volume of distribution is 25.0 L.
A near-complete subcutaneous bioavailability is unusual among the peptides on this site and it has a practical consequence: with this molecule, the amount injected and the amount absorbed are close to the same number, so an error in the draw translates almost directly into an error in exposure rather than being partly absorbed away.
What the label reports as adverse reactions
Nausea is the dominant one and the figure is large: 40% of patients receiving up to 8 monthly doses reported it, 13% required anti-emetic therapy for it, and 8% discontinued treatment because of it. Flushing occurred in 20% of treated patients against under 1% on placebo. The reactions reported above 4% are nausea, flushing, injection site reactions, headache and vomiting.
A 40% nausea rate is worth stating plainly because it is not a rare or idiosyncratic response — it is the expected experience of a substantial minority at the approved dose, in a trial population under supervision.
The contraindication that is easy to miss
VYLEESI is contraindicated in anyone with uncontrolled hypertension or known cardiovascular disease. That is not a general caution transplanted from the class — it follows from the drug's own measured effect, and it is the reason the approved product is dose-capped at one dose in 24 hours and no more than 8 doses per month.
Those limits are properties of a 1.75 mg dose delivered by an autoinjector holding 0.3 mL of ready-made solution. A vial of powder reconstituted at a concentration you chose has no such ceiling built into it, and nothing on the label describes how to reconstitute one, because the approved product never needed reconstituting.
Storage
The approved autoinjector is stored at or below 25°C (77°F), not frozen, and protected from light. There is no published stability data for a reconstituted PT-141 solution — no in-use window, no refrigerated shelf life, nothing — because no approved product is supplied as a powder. If you are holding one, the honest position is that how long it keeps is unknown rather than 28 days.
Common questions
Sources
Every number on this page comes from one of the documents below. Where no reliable source exists, the page says so instead of filling the gap.
- FDA labelFDA· 2019VYLEESI (bremelanotide) injection — FDA prescribing information