PT-141 (bremelanotide) is FDA-approved as Vyleesi, with defined labeling. This page explains how that label structures dosing and why — it is education about the medicine's design, not instructions. Dosing decisions belong to a prescriber working from the official labeling.
Overview
PT-141 dosing, as the approved label defines it, is on-demand: a single fixed dose of 1.75 mg injected subcutaneously at least 45 minutes before anticipated sexual activity, at most once in 24 hours and no more than 8 times per month (Vyleesi label, DailyMed). There is no titration schedule, no cycle, and no daily maintenance — a structure that follows directly from the drug's short half-life and its side-effect profile.
The pharmacology behind on-demand dosing
Bremelanotide is fast in, fast out. After subcutaneous injection its bioavailability is about 100%, plasma levels peak at roughly 1 hour, and the terminal half-life is about 2.7 hours (range 1.9–4.0); the peptide is cleared by hydrolysis of its amide bonds, with metabolites excreted mostly in urine (label, section 12.3).
That profile explains the whole dosing concept. A drug gone from the body within a day cannot build a steady state, so daily dosing would add nothing but cumulative side-effect exposure — and the melanocortin effect being sought is acute, tied to a window of activity. The 45-minute lead time matches the absorption curve: injected an hour before peak levels, the drug is near maximal concentration when it matters. Compare this with weekly peptides like semaglutide, where the engineering goal was the opposite — stretching half-life out to a week.
How the label structures use
The approved product is a single-use 1.75 mg/0.3 mL prefilled autoinjector, self-administered subcutaneously in the abdomen or thigh, as needed:
- At least 45 minutes before anticipated sexual activity — with the optimal window for each person judged by experienced benefit and side effects.
- No more than one dose per 24 hours.
- No more than 8 doses per month.
- Reassessed after 8 weeks — the label advises discontinuing if desire and distress have not improved.
These figures describe the label's structure, not a plan for any reader. Exact prescribing rules, special-population adjustments, and screening criteria live in the full prescribing information.
Why the limits exist
Each cap in the label maps to a measured effect:
One dose per 24 hours — every dose transiently raises blood pressure (up to ~6 mmHg systolic, peaking 2–4 hours post-dose) while lowering heart rate, typically resolving within 12 hours. Spacing doses prevents stacking that effect; the same physiology makes the drug contraindicated in uncontrolled hypertension and cardiovascular disease (label; ambulatory data in White et al. 2017).
Eight doses per month — skin darkening is frequency-dependent: focal hyperpigmentation occurred in 1% of women at the labeled pattern but in 38% of participants dosed daily for 8 days, and it did not always reverse (label).
The 8-week checkpoint — in the phase 3 trials the average benefit was modest (Kingsberg et al. 2019), and 40% of users experience nausea; if the trade-off isn't paying off within two months, the label's answer is to stop.
Autoinjector vs gray-market vials
The label's numbers assume the autoinjector: a sterile, pre-measured 1.75 mg every time. Gray-market PT-141 is sold as lyophilized powder that the buyer reconstitutes by hand, which means the actual delivered dose depends on vial content accuracy, diluent volume math, and syringe reading — three error sources the approved product was designed to eliminate. Unapproved nasal-spray versions revive a delivery route that development abandoned precisely because absorption was too variable (White et al. 2017). Label figures describe the approved product; they don't transfer to an unverified vial. Background on the compound itself: the main PT-141 page.