How to Reconstitute PT-141 (Bremelanotide): Storage, Stability, and Dosing After Mixing

Does the approved bremelanotide product need to be mixed?

No. Bremelanotide is approved as Vyleesi (NDA 210557, June 21, 2019) for premenopausal women with acquired, generalized hypoactive sexual desire disorder [1][2]. It is a 1.75 mg subcutaneous injection in a prefilled autoinjector pen, prescription only, injected into the abdomen or thigh as needed at least 45 minutes before anticipated sexual activity [1]. Because the pen is prefilled and self-administered, there is no reconstitution or dilution step [1].

What is sold as PT-141 powder?

Products sold as 'PT-141' are compounded or research-use peptides, not Vyleesi and not FDA-approved drugs; compounded drugs are not reviewed by FDA for safety, effectiveness or quality before marketing [3][1]. The Vyleesi label covers only the autoinjector. It gives no mixing, concentration or storage instructions for a compounded or research-use vial [1].

What does the label say about dosing?

The labeled Vyleesi dose is 1.75 mg subcutaneously, administered with the autoinjector [1]. The label says not to administer more than one dose within 24 hours and does not recommend more than 8 doses per month. It also says to stop after 8 weeks if symptoms have not improved. How long a single dose's effect lasts is unknown [1].

After a 1.75 mg dose, mean peak plasma concentration is 72.8 ng/mL, median time to peak about 1.0 hour, and mean terminal half-life about 2.7 hours (range 1.9 to 4.0) [1].

What the label says to watch for

Nausea is the most common adverse reaction: 40.0% on Vyleesi vs 1.3% on placebo in the pooled phase 3 trials (1,247 women; 627 on Vyleesi), with anti-nausea medicine needed by 13% and 8% discontinuing the trials because of it [1]. It was reported by 21% of patients after the first dose, falling to about 3% after later doses [1].

Each dose transiently raises blood pressure and lowers heart rate. Maximal increases were 6 mmHg systolic and 3 mmHg diastolic, peaking 2 to 4 hours after the dose, with heart rate down up to 5 beats per minute and values usually back to baseline within 12 hours [1]. Those figures are maximal, not average; in an 8-day ambulatory study of 127 women, mean daytime increases were 1.9 mmHg systolic and 1.7 mmHg diastolic [1]. Vyleesi is contraindicated in uncontrolled hypertension or known cardiovascular disease and is not recommended for people at high cardiovascular risk [1].

Focal hyperpigmentation of the skin, gums or breasts was reported by 1% of patients taking up to 8 doses a month, versus none on placebo; in another study, 38% developed it after 8 days of daily dosing and a further 14% after 8 more days [1].

Who Vyleesi is for

Vyleesi is not indicated for HSDD in postmenopausal women or in men, and not to enhance sexual performance [1].