PROTOCOLS // AS DOCUMENTED
PT-141 Dosage: What the Label and the Studies Document
The approved dose, the half-life, and the routes studied — reported as documented, never as a recommendation.
The short version
The PT-141 dosage that has real documentation is the approved one for women: 1.75 mg, given as a subcutaneous (under-the-skin) injection, used as needed before anticipated sexual activity, no more than one dose in 24 hours and no more than 8 doses a month [7]. "As needed" means it is not a daily drug.
This page reports what the FDA label and the published trials describe. It is not dosing advice, and no number here is a recommendation for any individual. The half-life — how long it takes the body to clear half a dose — is about 2.7 hours [7], which is part of why it is taken close to when it is wanted rather than on a schedule. Anything sold outside the approved drug has no verified dose, purity, or concentration [7].
PT-141 dosage: the approved regimen
The US prescribing information specifies a 1.75 mg subcutaneous dose, taken as needed at least 45 minutes before anticipated sexual activity, with a hard ceiling of one dose per 24 hours and no more than 8 doses per month [7]. The approved indication is acquired, generalized hypoactive sexual desire disorder in premenopausal women — and only that [7].
Earlier Phase 2 subcutaneous dose-finding in women tested 0.75, 1.25, and 1.75 mg before the 1.75 mg dose was selected [7]. These are documented research and label figures, reported here as such; this site recommends no dose to anyone and describes what was administered in studies, not what a reader should do.
How long does PT-141 last: half-life and pharmacokinetics
After subcutaneous injection, bremelanotide reaches peak blood levels quickly — median Tmax around 0.5 to 1.0 hours — and has a terminal half-life of approximately 2.7 hours (range 1.9-4.0 hours) per the prescribing information [7]. Early intranasal studies reported a similar half-life of about 1.85-2.09 hours [7].
The rest of the pharmacokinetics: volume of distribution about 25 L, clearance about 6.5 L/hr, roughly 21% serum protein binding, with elimination split 64.8% renal and 22.8% fecal in a radiolabeled study [7]. In practical terms, a short half-life is why the drug is dosed close to when an effect is wanted rather than maintained continuously. "How long does PT-141 last" therefore has two answers: it clears the blood within hours, but a single fMRI study found the desire effect measurable for up to 24 hours [5].
PT-141 dosage for women versus the research routes
The only fully approved PT-141 dosage for women is the 1.75 mg subcutaneous as-needed regimen above [7]. The preclinical female work that motivated it — the selective increase in solicitational behavior — was done in rats at research dose ranges, not human doses [2].
Other routes appear in the development history but not in current approval. Intranasal dosing was studied early in men and discontinued due to pharmacokinetic variability; intravenous dosing was used in early pharmacology [7]. A Phase 1 obesity research protocol gave subcutaneous doses up to 2.5 mg, up to three times daily for 15 days — a research protocol only, never an approved use, and the source of the appetite-related observations [7]. The cyclic-lactam structure gives PT-141 more stability than linear melanocortin peptides, which is part of why the subcutaneous route works [7].