PT-141 is the research name for bremelanotide, sold in the US as Vyleesi for premenopausal women with acquired, generalized hypoactive sexual desire disorder: low desire that causes distress. “How long does it last” sounds like one question, but it has at least four answers, and only some of them have been measured.
Clock one: how long the drug stays in the blood
After an injection under the skin, bremelanotide reaches its highest blood level at a median of about 1.0 hour, with a range of 0.5 to 1.0 hours [1]. Essentially all of the dose gets into the circulation, and injecting into the abdomen or the thigh made no meaningful difference to exposure.
From there it is cleared quickly, because it is a small peptide of 7 amino acids that the body breaks down by cutting its amide bonds [1]. The label gives a mean terminal half-life of about 2.7 hours, ranging from 1.9 to 4.0 hours between people.
A common pharmacology rule of thumb is that a drug is mostly gone after about five half-lives. By that rule, which is an estimate and not a figure from the label, a single dose would be largely cleared in roughly 13 hours.
Kidney function changes how much of the drug the body is exposed to. With severe kidney impairment, total exposure to a single dose doubled, and with moderate impairment it rose 1.5-fold [1].
0 min
Injection under the skin
The label says to inject at least 45 minutes before anticipated sexual activity.
About 1 hour
Peak blood level
Median time to peak 1.0 hour, range 0.5 to 1.0 hours.
2 to 4 hours
Peak rise in blood pressure
Up to 6 mmHg systolic and 3 mmHg diastolic, with heart rate down by up to 5 beats per minute.
About 2.7 hours
Half the drug cleared
Mean terminal half-life; range 1.9 to 4.0 hours.
Within 12 hours
Blood pressure and heart rate usually back to baseline
Readings 12 to 24 hours after a dose matched pre-dose values in a monitoring study.
Clock two: how long the effect on desire lasts
This is the answer most people want, and it is the one nobody has. The label states that the duration of efficacy after each dose is unknown, and that the best window for taking it has not been fully characterized [1]. It leaves timing to each patient, based on how long they feel the effect on desire and how much nausea they get.
Part of the reason lies in how the trials measured success. Their main desire questions asked women to look back over the past 4 weeks, and the distress question used a 30-day recall [1]. A month-long average can show that desire improved, but it cannot say whether each dose worked for two hours or twelve.
How much it improved is covered in detail in the review of the bremelanotide approval and trials. In brief, across the two 24-week RECONNECT trials, desire scores rose by 0.35 points more than on placebo, on a scale running from 1.2 to 6 [2]. Distress about low desire fell by 0.33 points more than on placebo.
Use was occasional rather than daily. Across both trials the median participant injected 10 times in 24 weeks, and most used it two to three times a month and no more than once a week [1].
Clock three: how long the side effects last
Nausea was the most common reaction in the phase 3 trials, reported by 40% of women on bremelanotide, and 8% left the trials because of it [1]. The label’s counseling section says it most commonly lasts about two hours after a dose, but can last longer, and that for most patients it improves with the second dose.
The blood pressure effect is short but measurable. In an ambulatory monitoring trial of 397 premenopausal women, systolic pressure rose by about 3 mmHg over placebo at 1.75 mg in the first 4 hours after each of two doses given 24 hours apart [3]. Its peak increases typically lasted less than 15 minutes, and heart rate fell by 4.6 to 4.7 beats per minute over the same window.
2.7 h
mean half-life of bremelanotide after one injection (range 1.9 to 4.0 h)
Vyleesi label
40%
of women on bremelanotide reported nausea in the phase 3 trials; 8% stopped because of it
Vyleesi label
< 15 min
typical length of peak blood pressure increases after a 1.25 or 1.75 mg dose (n = 397)
White 2017
Clock four: does the benefit last over months?
Women who finished the 24-week trials could continue in a 52-week open-label extension [4]. Of 856 eligible, 684 joined and 272 completed it, so most did not reach the end.
Among those who had taken bremelanotide from the start, desire scores at the end of the extension were 1.25 to 1.30 points above their original baseline [4]. Everyone knew they were on the drug and there was no placebo arm, so the authors analyzed these results descriptively only.
Nausea stayed the most common related side effect, at 40.4%, followed by flushing at 20.6% and headache at 12.0%. The authors reported no new safety signals over the year.
What this means if you are considering it
The pharmacology gives a short, predictable blood-level curve. The part that matters most, the window in which desire is affected, has never been timed, so expect some trial and error with a prescriber. The label’s dose and limits are set out in PT 141 dosage.
The approved product is an injection under the skin. For other options with human studies behind them, the sexual health goal page brings them together. Questions about a nasal version are covered in PT-141 nasal spray.
What the evidence says about peptides and inflammation is gathered in peptides for inflammation.