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Biologic Description
PT-141, also known as bremelanotide, is a peptide and a tanning melanocortin receptor agonist primarily targeting MC4R, which plays a crucial role in enhancing sexual desire and arousal in both men and women. This compound has gained notable recognition through studies such as "PT-141: a melanocortin agonist for the treatment of sexual dysfunction" and "Salvage of sildenafil failures with bremelanotide," underscoring its potential in addressing sexual dysfunctions.
Originally identified from research on α-MSH, a hormone involved in skin pigmentation and sexual behavior, PT-141 evolved as a synthetic derivative aimed at sexual function enhancement. Approved in 2019 by the FDA for treating hypoactive sexual desire disorder (HSDD) in premenopausal women, it's commercially available under the brand Vyleesi. Palatin Technologies, the developer, markets this drug in auto-injection pens.
PT-141 is specifically developed by modifying the structure of Melanotan II to enhance its efficacy in treating sexual dysfunction. This modification focuses on its ability to selectively activate certain melanocortin receptors in the body, particularly MC4R, which is involved in sexual arousal. Unlike Melanotan II, PT-141 does not significantly affect skin pigmentation, which was a primary characteristic of Melanotan II. This targeted action makes PT-141 distinct and specifically effective for its intended medical uses.
Beyond treating HSDD in women, PT-141's scope extends to potential applications in erectile dysfunction (ED) and other sexual dysfunctions. Acting on melanocortin receptors, which are linked to sexual desire and appetite, PT-141 after subcutaneous injection reaches peak levels in about an hour, offering almost immediate effects on male sexual desire.
Clinical trials have highlighted PT-141's benefits, especially for treating ED in men who don't respond to sildenafil (Viagra). Studies demonstrated significant increases in erection duration and erectile response, indicating its effectiveness. Moreover, PT-141's activation of presynaptic MC4Rs increases dopamine release, beneficial in treating HSDD in women. Research showed that women experienced more sexually satisfying events and reduced distress related to intercourse.
PT-141's role isn't limited to HSDD or ED; it has broader implications for general sexual dysfunction treatment. It has shown effectiveness in triggering sexual desire irrespective of the initial sexual stimulation, suggesting a versatile potential in addressing various sexual desire disorders.
Dosage Guidelines
PT-141 used for treating low sexual desire in women, is typically administered through self-injection subcutaneously. The standard dosage is 1.75 mg, usually taken about 45 minutes before sexual activity. Women with hypoactive sexual desire disorder (HSDD) who are prescribed bremelanotide should use it no more than once daily and not exceed eight doses per month. If adverse reactions occur, the dosage can be lowered, with research indicating that even a reduced dose of 1.25 mg can be effective.
In studies involving men, both with and without erectile dysfunction (ED), PT-141, the active ingredient in bremelanotide, has been administered in doses ranging from 1 to 10 mg subcutaneously. These studies have shown that doses above 1 mg can yield significant results, with dose-dependent improvements in erectile function observed at doses up to 20 mg. For treating erectile dysfunction, a starting dose of 1 mg is suggested, based on research findings. These studies highlight the versatility and efficacy of PT-141 in treating sexual dysfunction in both men and women, offering dose-dependent improvements while maintaining a balance with potential side effects.
Prescribing guidelines recommend no more than 1 dose in 24 hours and no more than 8 doses per month. Individuals should discontinue use after 8 weeks without benefit. Women seem to be more responsive to smaller .75mg doses. It is also best to do a smaller dose loading period before larger sexual dosages.
.75-1.25 mg
45 minutes before sex
as needed
Side Effects
PT-141, also known as bremelanotide, is associated with a range of side effects, particularly when used for treating low sexual desire in women at the recommended dose of 1.75 mg. The most common of these include nausea, affecting about 40% of users and often more prominent with the first injection, flushing in 20% of users, reactions at the injection site for 13%, and headaches in 11% of those treated.
Beyond these common effects, PT-141 may also cause less frequent but more serious adverse reactions.
These include increases in blood pressure, severe nausea, vomiting, joint pain (arthralgia), restless leg syndrome, and localized hyperpigmentation.
Due to its potential impact on blood pressure and heart rate, bremelanotide is advised against for individuals who are pregnant or suspected of being pregnant, those with cardiovascular disease, or anyone diagnosed with uncontrolled hypertension.
While rare, PT-141 can lead to elevated serum enzyme levels and, in very rare cases, acute liver damage. Despite these risks, PT-141 has demonstrated a favorable safety profile in treating low sexual desire in women, backed by successful phase 3 clinical trials leading to its FDA approval in the United States in 2019.
For male sexual desire, preliminary trials have established the safety and efficacy of PT-141. It has shown potential as a potent initiator of erection with minimal side effects, though it is important to note that PT-141 is not yet approved for treating male sexual dysfunction and is mainly available for research purposes.
References:
Bremelanotide: New Drug Approved for Treating Hypoactive Sexual Desire Disorder
Bremelanotide is a subcutaneous injection that can be administered as needed approximately 45 minutes prior to sexual activity. Bremelanotide is safe and has limited drug-drug interactions, including no clinically significant interactions with ethanol. Prescribing guidelines recommend no more than 1 dose in 24 hours and no more than 8 doses per month. Individuals should discontinue use after 8 weeks without benefit. Bremelanotide demonstrates significant improvement in desire and a significant decrease in distress related to lack of desire. Bremelanotide is the second Food and Drug Administration-approved medication for the treatment of HSDD.
Author: Margret I. Moréa, David Kenleyb
Publication Date: June 2014
Double-blind, placebo-controlled evaluation of the safety, pharmacokinetic properties and pharmacodynamic effects of intranasal PT-141, a melanocortin receptor agonist, in healthy males and patients with mild-to-moderate erectile dysfunction
PT-141, a cyclic heptapeptide melanocortin analog, was evaluated following intranasal administration in healthy male subjects and in Viagra-responsive erectile dysfunction (ED) patients. Erectile response was assessed by RigiScan trade mark in healthy subjects without visual sexual stimulation (VSS) and in Viagra-responsive ED patients with VSS. In healthy subjects, mean C(max) and AUC((0-t)) increased in a dose-dependent manner. Median T(max) was 0.50 h and mean t(1/2) ranged from 1.85 to 2.09 h. In both studies, an erectile response induced by PT-141 administration was statistically significant, compared to placebo, at doses greater than 7 mg, with the onset of the first erection occurring in approximately 30 min. PT-141 was safely administered and well tolerated in both studies. A maximum-tolerated dose was not identified. Flushing and nausea were the most common adverse events reported in both studies and no clinically significant changes in vital signs, laboratory tests, ECGs, or physical exams were observed. Based upon its erectogenic potential and tolerability profile, PT-141 is a promising candidate for further evaluation as a treatment for male ED.
Authors: L E Diamond, D C Earle, R C Rosen, M S Willett, P B Molinoff
Published: 2004 Feb
PT-141: a melanocortin agonist for the treatment of sexual dysfunction
PT-141, a synthetic peptide analogue of alpha-MSH, is an agonist at melanocortin receptors including the MC3R and MC4R, which are expressed primarily in the central nervous system. Administration of PT-141 to rats and nonhuman primates results in penile erections. Systemic administration of PT-141 to rats activates neurons in the hypothalamus as shown by an increase in c-Fos immunoreactivity. Neurons in the same region of the central nervous system take up pseudorabies virus injected into the corpus cavernosum of the rat penis. Administration of PT-141 to normal men and to patients with erectile dysfunction resulted in a rapid dose-dependent increase in erectile activity. The results suggest that PT-141 holds promise as a new treatment for sexual dysfunction.
Authors: P B Molinoff, A M Shadiack, D Earle, L E Diamond, C Y Quon
Published: 2003 Jun
Salvage of Sildenafil Failures With Bremelanotide: A Randomized, Double-Blind, Placebo Controlled Study
Positive clinical results were seen in 51 (33.5%) patients in the bremelanotide group compared with 13 (8.5%) patients in the placebo group (p = 0.03). Patients in the bremelanotide group reported significantly greater intercourse satisfaction than those in placebo group (p = 0.03). More drug related adverse effects occurred in the bremelanotide group (p = 0.01).
Authors: Mohammad Reza Safarinejad and Seyyed Yousof Hosseini
Published: Mar 2008