PT-141 (10 mg)

At a Glance

PT-141 (Bremelanotide) is a melanocortin MC4R agonist that increases sexual desire centrally via dopamine release in the hypothalamus — the pharmacological basis for its 2019 FDA approval as Vyleesi for hypoactive sexual desire disorder (HSDD) in premenopausal women. Unlike PDE5 inhibitors, PT-141 acts on desire rather than genital blood flow and does not require sexual stimulation to produce effects.[2]

• Reconstitute: Add 3.0 mL bacteriostatic water → 3.33 mg/mL (3,333 mcg/mL) concentration.
• Starting dose: 500 mcg SC (15 units / 0.15 mL) for the first 4 weeks — tolerance phase.
• Easy measuring: At 3.33 mg/mL on a U-100 syringe, 1 unit = 0.01 mL = 33.3 mcg.
• Timing: Inject 30–45 minutes before anticipated activity; maximum 1 dose per 24 hours.
• Storage: Lyophilised: freeze at −20 °C; reconstituted: refrigerate at 2–8 °C; use within 28–30 days.

Overview

• Goal: Research into central MC4R-mediated sexual desire modulation via melanocortin pathway activation and hypothalamic dopamine release.[3]
• Schedule: On-demand subcutaneous injection, 30–45 minutes before activity; maximum 1 dose per 24 hours.
• Dose range: 500 mcg (tolerance) → 1,500 mcg (upper research titration); FDA-approved reference: 1,750 mcg.
• Reconstitution: 3.0 mL BAC water per 10 mg vial → 3.33 mg/mL (3,333 mcg/mL).
• Storage: Lyophilised at −20 °C; reconstituted at 2–8 °C; use within 28–30 days.

What You’ll Need

Plan based on a 12-week titration protocol (Weeks 1–4: 500 mcg; 5–8: 1,000 mcg; 9–12: 1,500 mcg), dosing 3 times per week. Total dose ≈ 54,000 mcg (54 mg).

• PT-141 Vials (10 mg each): 54 mg cumulative → 6 vials.
• Insulin Syringes (U-100, 1 mL): 36 injections over 12 weeks → 40 syringes.
• Bacteriostatic Water (10 mL bottles): 3.0 mL per vial → 2 × 10 mL bottles.
• Alcohol Swabs: 2 per injection → 80 swabs for the course.

How to Reconstitute

1. Allow the frozen lyophilised vial to reach room temperature (10–15 minutes). Do not apply heat.
2. Draw 3.0 mL bacteriostatic water into a sterile syringe using a clean needle.
3. Wipe the vial stopper with a fresh alcohol swab; allow to air-dry. Inject the bacteriostatic water slowly down the inner wall of the vial — do not inject directly onto the powder cake.
4. Gently swirl or roll the vial until the powder is fully dissolved — do not shake. The solution should be clear and colourless. Any cloudiness or particulate matter is cause for discard.
5. Label the vial with the reconstitution date. Refrigerate at 2–8 °C, protected from light. Use within 28–30 days.

Dosing Schedule

Frequency: Inject on demand, 30–45 minutes before anticipated sexual activity. Maximum 1 dose per 24 hours. The FDA-approved regimen specifies no more than 8 doses per month; the same restriction is prudent at all research doses to minimise cumulative hyperpigmentation risk. At the FDA-approved dose of 1,750 mcg, a 10 mg vial provides approximately 5–6 doses. At the 500 mcg tolerance dose, a single vial provides 20 doses.[2]

Protocol Details

• Weeks 1–4 (tolerance): 500 mcg (15 units / 0.15 mL) SC, 30–45 min before activity.[2]
• Weeks 5–8: 1,000 mcg (30 units / 0.30 mL) SC — advance only if 500 mcg was well tolerated.
• Weeks 9–12: 1,500 mcg (45 units / 0.45 mL) SC.
• Reference FDA dose: 1,750 mcg (53 units / 0.53 mL) SC — the approved Vyleesi dose for HSDD.[1]
• Injection site: Abdomen or thigh preferred. Rotate sites between doses.
• Maximum frequency: 1 dose per 24 hours; ≤8 doses per month recommended.

Storage

• Lyophilised: Store at −20 °C (−4 °F) or below; protect from light and moisture.
• Reconstituted: Refrigerate at 2–8 °C. Do not freeze. Use within 28–30 days.
• Appearance: Clear and colourless. Discard if cloudy, coloured, or particulate.

How PT-141 Works

PT-141 is a synthetic cyclic heptapeptide (Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-OH; MW 1,025.2 Da) derived from Melanotan II. Its cyclic structure confers metabolic stability and selective receptor binding compared to the linear parent compound. After subcutaneous injection, PT-141 is absorbed rapidly, reaching peak plasma concentration at approximately Tmax ≈ 1 hour, with a half-life of approximately 2.7 hours and near-complete SC bioavailability.[2]

PT-141 activates melanocortin receptors MC1R, MC3R, MC4R, and MC5R, with the sexual desire effect driven primarily by MC4R agonism in the medial preoptic area (mPOA) of the hypothalamus. MC4R activation in the mPOA disinhibits mesolimbic dopaminergic neurons, increasing dopamine release in the nucleus accumbens — the brain’s primary reward and motivation centre. This central mechanism accounts for the increase in sexual desire and motivation observed clinically, and explains why PT-141 is effective independent of vascular function and without requiring pre-existing arousal.[3]

Good to Know

• Blood pressure: PT-141 produces a transient mean systolic BP increase of ≈6 mmHg, peaking at 2–4 hours post-dose and fully resolved within 12 hours.[2] Do not use in individuals with uncontrolled hypertension or cardiovascular disease. Check BP before dosing; withhold if >130/80 mmHg.
• Nausea management: Nausea affects ≈40% of users at 1.75 mg. At lower titration doses, incidence is reduced. If nausea is a concern, a prophylactic antiemetic (e.g., ondansetron) taken 30 minutes prior is a strategy used in some research protocols. Eating a light meal before injection may also reduce GI effects.
• Hyperpigmentation: Focal hyperpigmentation occurs in ≈1% at on-demand dosing but rises to 38% with daily use. Keep dosing frequency ≤8 times per month. Pigmentation is a MC1R-mediated effect and is dose- and frequency-dependent.
• Gastric motility: PT-141 slows gastric emptying; avoid co-administration of oral medications with narrow therapeutic windows within 8 hours of dosing. Oral naltrexone bioavailability is specifically reduced by PT-141.
• No sexual stimulation required for central effects, but the presence of desire following PT-141 does not guarantee erection or lubrication in the absence of other facilitating factors.
• Vial doses per concentration (10 mg / 3.0 mL → 3,333 mcg/mL): 500 mcg = 20 doses; 1,000 mcg = 10 doses; 1,500 mcg = 6–7 doses; 1,750 mcg (FDA dose) = 5–6 doses.
• HSDD efficacy (Phase 3 RCT, premenopausal women): Statistically significant improvements in sexually satisfying events and FSDS-DAO desire score vs. placebo across two pivotal trials. An independent re-analysis characterises effect sizes as small.[2]
• Nausea: 40% at 1.75 mg; principal tolerability limitation. Lower titration doses expected to reduce incidence.
• Flushing: 20.3%; typically transient and not requiring intervention.
• Injection site reactions: 13.2%; bruising, pain, local discomfort.
• Headache: 11.3%; resolves without treatment in most cases.
• Blood pressure elevation: Mean +6 mmHg systolic (transient; resolves within 12 hours). Monitor BP, particularly in early titration.[2]
• Focal hyperpigmentation: 1% at ≤8 doses/month; up to 38% with daily dosing — keep frequency within limits.
• Vomiting: 4.8% at FDA dose; reduced at lower titration doses.
• For background on PT-141's mechanism, evidence, and safety profile, see What Is PT-141?.

Tips for Best Results

• Begin at 500 mcg for at least 4 weeks before advancing; slower titration significantly reduces nausea and cardiovascular side effects.
• Measure blood pressure before each dose during the first 4 weeks; withhold if systolic >130 mmHg.
• Plan dosing 45 minutes before anticipated activity to align timing with the ≈1-hour Tmax.
• Eat a light meal before injection; fasting may increase nausea sensitivity.
• Track each dose date to stay within the 8-doses-per-month guideline and limit hyperpigmentation risk.
• Store the vial upright in the refrigerator and inspect for particulate matter before each use; discard any vial past 30 days post-reconstitution.

Injection Tips

• Clean the vial stopper and injection site with separate alcohol swabs; allow both to air-dry fully before proceeding.
• Using a 29–31 gauge insulin syringe (5/16″ to 1/2″ needle), draw the calculated dose precisely.
• Pinch a fold of skin and insert the needle at 45° into subcutaneous fat (90° is acceptable with a short needle into a well-pinched fold).
• Inject slowly over 2–3 seconds; do not aspirate. Withdraw the needle, apply gentle pressure, and do not rub the site.
• Rotate injection sites (abdomen, thighs, upper arms) and dispose of each syringe in a sharps container immediately after use.