MEDICAL DISCLAIMER: Educational research guidelines only. Lyophilized peptides are investigational chemical compounds and are NOT approved for human consumption, diagnosis, or therapy. Consult a licensed physician before any research application.
PT-141 Dosage Chart, Schedule & Reconstitution Protocol
Quickstart Highlights
PT-141 (bremelanotide) is a cyclic heptapeptide melanocortin receptor agonist derived from the alpha-melanocyte-stimulating hormone (alpha-MSH) backbone, originally developed from the Melanotan II scaffold by Palatin Technologies after observation of sexual side effects during early tanning research. It binds MC3R and MC4R in the central nervous system, with the MC4R-mediated action on hypothalamic paraventricular and limbic circuits driving the prosexual effect that distinguishes it from PDE5 inhibitors, which act peripherally on penile vasculature without engaging central desire circuits. The FDA approved bremelanotide as Vyleesi in June 2019 for premenopausal hypoactive sexual desire disorder (HSDD), administered as a 1.75 mg subcutaneous autoinjector. Researchers also study off-label PT-141 for male erectile dysfunction unresponsive to PDE5 inhibitors and for post-SSRI sexual dysfunction. Pivotal phase 3 RECONNECT data appear in PMID 31188211, with pharmacology context in PMID 29017371.
Reconstitute: Add 3 mL bacteriostatic water → 3.33 mg/mL concentration.
Easy measuring: At 3.33 mg/mL, 1 unit = 0.01 mL = 0.0333 mg (33 mcg) on a U-100 insulin syringe.
Storage: Lyophilized frozen; reconstituted refrigerated; avoid repeated freeze–thaw.
Plasma half-life: Approximately 2.7 hours after subcutaneous administration of the approved 1.75 mg dose, with central effects on sexual desire reported to persist 4 to 8 hours beyond Cmax.
Onset: Effects on desire and arousal typically appear 30 to 60 minutes after subcutaneous injection; Vyleesi labeling recommends dosing at least 45 minutes before anticipated activity.
Regulatory status: FDA approved (Vyleesi, June 2019) for premenopausal HSDD only. Male erectile dysfunction and post-menopausal use are off-label and not supported by approved labeling.
Hyperpigmentation risk: Focal hyperpigmentation of the face, gums, and breasts has been reported in approximately 1 percent of subjects in pivotal trials, attributed to MC1R cross-reactivity and more common with repeated dosing.
Quick Protocol Navigation
Reconstitution Instruction & Mixing Step-by-Step
Lyophilized powder must be reconstituted carefully. Agitating peptide chains can shear disulfide bonds and render the peptide biologically inert.
Draw 3.0 mL bacteriostatic water with a sterile syringe.
Inject slowly down the vial wall; avoid foaming.
Gently swirl/roll until dissolved (do not shake).
Inject slowly; wait a few seconds before withdrawing the needle.
Do not aspirate for subcutaneous injections; inject slowly and steadily[7].
Interactive PT-141 Syringe Calculator
Currently visualizing the 10 mg vial reconstituted with 3 mL bacteriostatic water. Adjust the target dose to dynamically render syringe units.
Reconstitution Calculation: 10mg dry powder in 3mL water yields 3.33 mg/mL. To evaluate a 250mcg dose, pull to 7.5 units (8 syringe ticks).
U-100 Syringe Representation
7.5 Units (8 Ticks)
Educational reference visual. Assumes standard U-100 insulin syringe where 1.0 mL volume = 100 units.
Titration & Dose Escalation Schedules
| Week | Daily Dose (mcg) | Units (per injection) (mL) |
|---|---|---|
| Weeks 1–8 | 500 mcg (0.5 mg) | 15 units (0.15 mL) |
| Weeks 9–12 | 1000 mcg (1.0 mg) | 30 units (0.30 mL) |
| Weeks 13–16 | 1500 mcg (1.5 mg) | 45 units (0.45 mL) |
Administration guidelines: Refer to guidelines | 3 mL Reconstitution
| Concentration (mcg/mL) | Pump Output (mL/actuation) | Amount per Actuation (mcg) | Actuations per mL | Total Actuations in Reconstituted Volume |
|---|---|---|---|---|
| [A] | [B] | [A] × [B] | 1 / [B] | [Recon. vol. mL] × (1 / [B]) |
| [C] | [D] | [C] × [D] | 1 / [D] | [Recon. vol. mL] × (1 / [D]) |
Administration guidelines: Refer to guidelines | 3 mL Reconstitution
Research Supplies Quantity Planner
Scientific mathematical planning of syringes, bacteriostatic water and dry vials needed for extended research blocks using the 10 mg vial.
Peptide Vials (PT-141, 10 mg each):
- check8 weeks (56 days × 500 mcg = 28 mg) ≈ 3 vials
- check12 weeks (56 × 500 + 28 × 1000 = 56 mg) ≈ 6 vials
- check16 weeks (56 × 500 + 28 × 1000 + 28 × 1500 = 98 mg) ≈ 10 vials
Insulin Syringes (U-100):
- checkPer week: 7 syringes (1/day)
- check8 weeks: 56 syringes
- check12 weeks: 84 syringes
- check16 weeks: 112 syringes
Bacteriostatic Water (10 mL bottles): Use ~3.0 mL per vial for reconstitution.
- check8 weeks (3 vials): 9 mL → 1 × 10 mL bottle
- check12 weeks (6 vials): 18 mL → 2 × 10 mL bottles
- check16 weeks (10 vials): 30 mL → 3 × 10 mL bottles
Alcohol Swabs: One for the vial stopper + one for the injection site each day.
- checkPer week: 14 swabs (2/day)
- check8 weeks: 112 swabs → recommend 2 × 100-count boxes
- check12 weeks: 168 swabs → recommend 2 × 100-count boxes
- check16 weeks: 224 swabs → recommend 3 × 100-count boxes
Mechanism of Action (MOA)
Bremelanotide is a cyclic heptapeptide melanocortin receptor agonist developed as a structural analog of alpha-MSH with improved metabolic stability and modified receptor selectivity profile. The peptide engages all four peripheral melanocortin receptor subtypes (MC1R through MC5R) with relatively modest selectivity, but its sexual function effects are mediated primarily through MC4R, a Gs-coupled receptor highly expressed in the medial preoptic area, paraventricular nucleus, ventral tegmental area, and other limbic structures involved in sexual desire and arousal [1][2]. MC4R activation in the medial preoptic area is hypothesized to enhance dopaminergic tone in mesolimbic reward circuits, increasing the salience and motivational drive associated with sexual stimuli rather than producing a peripheral vasoactive or hormonal effect. This central mechanism distinguishes bremelanotide from phosphodiesterase-5 inhibitors (sildenafil, tadalafil), which act peripherally on penile or vulvovaginal blood flow. The plasma half-life of subcutaneous bremelanotide is approximately 2.7 hours, with Cmax reached within 1 hour and clearance primarily renal [6]. The standard route of administration is subcutaneous autoinjector (1.75 mg, Vyleesi) injected in the thigh or abdomen, with effects on subjective sexual desire emerging within 45 minutes and persisting for approximately 10 to 16 hours [4]. Earlier development of intranasal bremelanotide was discontinued due to dose-limiting blood pressure elevations at the doses required for efficacy [3]. Beyond the FDA-approved indication of HSDD in premenopausal women, off-label and research applications include male erectile dysfunction (particularly in men who do not respond to or cannot tolerate PDE5 inhibitors), generalized sexual desire complaints in postmenopausal women, and exploratory work in body image and reward processing in eating disorder research. Downstream effects documented in clinical trials include increased Female Sexual Function Index (FSFI) total and domain scores, reductions in Female Sexual Distress Scale-Desire/Arousal/Orgasm scores, and modest improvements in satisfying sexual events in the RECONNECT trials [4][5]. The drug does not require regular daily use and is not contraceptive; it does not treat hormonal causes of low desire (estrogen or testosterone deficiency) and should be considered an adjunct rather than a replacement for relationship-based or psychological treatment of sexual dysfunction. Common research uses extend to studies on melanocortin signaling in pigmentation, appetite regulation (MC4R is the strongest known monogenic obesity gene), and energy balance, although bremelanotide has not been developed clinically for those indications. The differentiation from flibanserin (Addyi), the other FDA-approved HSDD therapy in premenopausal women, is important: flibanserin is a daily oral serotonin-modulating agent with a different mechanism, slow-onset cumulative effects, and significant alcohol and CYP-interaction restrictions, whereas bremelanotide is an on-demand subcutaneous injection with rapid onset, no daily dosing requirement, and a different adverse event profile dominated by nausea, flushing, and transient blood pressure elevation. Practical research and clinical use of bremelanotide therefore requires patient selection for tolerability of the nausea profile, cardiovascular screening to exclude uncontrolled hypertension, contraception for women of childbearing age, and counseling about pigmentary effects with repeated use.
Clinical Trial Efficacy Highlights
- starRECONNECT-1 and RECONNECT-2 (Kingsberg et al., Obstet Gynecol 2019) enrolled approximately 1,200 premenopausal women with acquired generalized HSDD; 1.75 mg subcutaneous bremelanotide on demand for 24 weeks significantly improved sexual desire (FSFI-Desire) and reduced distress (FSDS-DAO Q13) with both co-primary endpoints meeting p less than 0.001 in the integrated analysis [4].
- starDiamond, Earle, Heiman, Rosen and colleagues published in J Sex Med 2006 the foundational proof-of-concept study showing that intranasal bremelanotide improved subjective sexual arousal and desire in premenopausal women with sexual arousal disorder, providing the rationale for further phase 2 and 3 development [3].
- starSafarinejad and colleagues (2008) conducted a randomized double-blind placebo-controlled fixed-dose study of intranasal bremelanotide in women with female sexual arousal disorder and reported significant improvement in subjective and physiological measures of arousal, complementing the Diamond data and the later RECONNECT subcutaneous results [7].
- starPrespecified subgroup analyses of RECONNECT (Simon et al., 2022) demonstrated consistent treatment effects across age, race, baseline FSFI severity, and antidepressant co-administration subgroups, supporting broad applicability of the approved indication [8].
- starAn open-label 52-week extension of RECONNECT showed maintenance of efficacy across longer-term use with no new safety signals, supporting the favorable benefit-risk profile underlying FDA approval in 2019 [4].
- starPhase 2 trials in men with erectile dysfunction not responsive to PDE5 inhibitors have shown modest improvements in erectile function with bremelanotide, but development for male ED was deprioritized in favor of the female HSDD indication [9].
- starIn healthy volunteers, single doses of bremelanotide produce transient mild increases in systolic blood pressure of 1.9 to 6.0 mmHg lasting up to 16 hours, the pharmacologic effect that led to discontinuation of the higher-dose intranasal program and underlies current cardiovascular safety guidance [10].
Side Effects & Tolerability Profile
Clinical subjects transiently report mild side effects. Slowly escalating the titration dose represents the single most effective intervention to limit side effects.
- warningNausea is the most common adverse event, occurring in approximately 40 percent of users in the RECONNECT trials, generally most pronounced with the first one to two doses and improving with continued use; concomitant antiemetic use is permitted.
- warningFlushing was reported in approximately 20 percent of users; headache in approximately 11 percent; and injection site reactions in approximately 13 percent across the RECONNECT integrated dataset [4].
- warningTransient mild blood pressure elevation (systolic increase of approximately 6 mmHg) lasts up to 16 hours after dosing; bremelanotide is contraindicated in patients with uncontrolled hypertension or known cardiovascular disease, and the maximum dosing frequency is 8 doses per month.
- warningFocal hyperpigmentation has been reported with repeated use, particularly in the face, gums, and breasts, due to MC1R activation; this effect is more common in patients with darker skin tones and may not fully reverse on discontinuation.
- warningHeadache, vomiting, and dizziness occur in 5 to 11 percent of users; severe nausea leading to discontinuation occurs in 8 percent of treated subjects in the registration trials.
- warningBremelanotide is contraindicated during pregnancy because of melanocortin-related teratogenicity concerns in animal studies; women must use effective contraception during treatment.
- warningDrug-drug interactions with oral medications include slowed gastric emptying that can reduce absorption of orally administered drugs (e.g., naltrexone, indomethacin); the Vyleesi label includes warnings about this effect.
Subcutaneous Injection Technique
Most research peptides require subcutaneous injection into fatty tissue. Never inject directly into a blood vessel or deep muscle tissue unless clinically detailed.
1. Site Selection
Common locations include the abdomen (2 inches from navel), outer upper arms, or thighs.
2. Sanitization
Thoroughly clean the selected site, stopper and vial top using 70% isopropyl alcohol prep swabs.
3. Angle & Push
Pinch the skin and insert the needle at a 45 to 90-degree angle. Depress plunger smoothly.
4. Site Rotation
Rotate injection sites continuously to avoid lipodystrophy or tissue scarring.
Frequently Asked Questions
What is the typical PT-141 dosage?expand_more
The FDA-approved dose for HSDD is 1.75 mg subcutaneous as needed approximately 45 minutes before anticipated sexual activity, with no more than one dose per 24 hours and no more than 8 doses per month. Earlier development used 0.75 to 1.75 mg subcutaneously in dose-finding studies.
How is PT-141 used in research protocols?expand_more
Research applications include premenopausal HSDD (the approved indication), male erectile dysfunction not responsive to PDE5 inhibitors, postmenopausal sexual dysfunction, and exploratory studies on melanocortin signaling in reward processing. Outcome measures include the Female Sexual Function Index, Female Sexual Distress Scale, and erectile function scales.
Can PT-141 be combined with other peptides?expand_more
Bremelanotide is sometimes combined off-label with PDE5 inhibitors in male ED protocols, although blood pressure effects warrant caution. Combinations with oxytocin in research on social and sexual cognition have been explored. Conventional hormonal therapy for hypogonadal causes of low desire should be addressed independently.
What are the side effects of PT-141?expand_more
Common adverse events include nausea (approximately 40 percent), flushing (20 percent), headache (11 percent), and injection site reactions (13 percent). Transient blood pressure elevation and focal hyperpigmentation are pharmacologic effects of melanocortin agonism. Contraindicated in uncontrolled hypertension and pregnancy.
Is PT-141 FDA approved?expand_more
Yes. Bremelanotide was FDA approved as Vyleesi on 21 June 2019 for acquired generalized hypoactive sexual desire disorder in premenopausal women. It is not approved for male erectile dysfunction, postmenopausal HSDD, or other indications, and is used off-label in those contexts.
Academic References & Study Citations
Molinoff PB, Shadiack AM, Earle D, Diamond LE, Quon CY. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003;994:96-102. View Scientific Paper →
Pfaus J, Giuliano F, Gelez H. Bremelanotide: an overview of preclinical CNS effects on female sexual function. J Sex Med. 2007;4 Suppl 4:269-279. View Scientific Paper →
Diamond LE, Earle DC, Heiman JR, Rosen RC, Perelman MA, Harning R. An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. J Sex Med. 2006;3(4):628-638. View Scientific Paper →
Kingsberg SA, Clayton AH, Portman D, et al. Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials. Obstet Gynecol. 2019;134(5):899-908. View Scientific Paper →
Clayton AH, Lucas J, DeRogatis LR, Jordan R. Phase I randomized placebo-controlled, double-blind study of the safety and tolerability of bremelanotide co-administered with ethanol in healthy male and female participants. Clin Ther. 2017;39(3):514-526. View Scientific Paper →
Vyleesi (bremelanotide) prescribing information. AMAG Pharmaceuticals, accessdata.fda.gov. View Scientific Paper →
Safarinejad MR, Hosseini SY. Salvage of sildenafil failures with bremelanotide: a randomized, double-blind, placebo controlled study. J Urol. 2008;179(3):1066-1071. View Scientific Paper →
Simon JA, Kingsberg SA, Goldstein I, et al. Prespecified and integrated subgroup analyses from the RECONNECT phase 3 studies of bremelanotide. J Womens Health (Larchmt). 2022;31(3):391-400. View Scientific Paper →
Rosen RC, Diamond LE, Earle DC, Shadiack AM, Molinoff PB. Evaluation of the safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141, a melanocortin receptor agonist, in healthy male subjects and in patients with an inadequate response to Viagra. Int J Impot Res. 2004;16(2):135-142. View Scientific Paper →
Edinoff AN, Sanders NM, Lewis KB, et al. Bremelanotide for treatment of female hypoactive sexual desire. Neurol Int. 2022;14(1):75-88. View Scientific Paper →