PT-141 (Bremelanotide) Dosing and Reconstitution

Last updated: July 2026

The only FDA-approved PT-141 dose is bremelanotide 1.75 mg injected subcutaneously as needed, at least 45 minutes before anticipated sexual activity, with no more than one dose in 24 hours. Compounded PT-141 instead arrives as a lyophilised powder you reconstitute with bacteriostatic water yourself, and the number of syringe units you draw depends entirely on how much water you add — not on the milligrams alone.

Have a PT-141 vial and a target dose? Work out the exact mL and U-100 syringe units in seconds.

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TL;DR — key takeaways

Approved dose is fixed. Vyleesi is a pre-filled autoinjector of 1.75 mg in 0.3 mL — no mixing, no maths, approved only for premenopausal women with acquired, generalised HSDD.
Compounded vials are DIY. A powder vial (often 5 mg or 10 mg) must be reconstituted, and your units depend on the concentration you create.
Units follow concentration. The same 1.75 mg dose is 35 units from a 5 mg/mL mix but only 17.5 units from a 10 mg/mL mix.
It is an as-needed peptide. PT-141 is a melanocortin receptor agonist taken before activity, not a daily protocol, and its effect is not dose-stacked.
Off-label use is unproven. Use in men, at higher doses, or by non-prescribed routes is not FDA-established — this page is arithmetic, not medical advice.

What PT-141 is and how it is dosed

PT-141 (bremelanotide) is a synthetic peptide analogue of alpha-melanocyte-stimulating hormone (α-MSH) that acts as an agonist at melanocortin receptors — principally MC4R and MC3R in the central nervous system. Unlike PDE5 inhibitors, it works centrally rather than on blood flow, which is why it was studied for sexual desire rather than purely erectile mechanics. It has a short half-life of roughly two to three hours, so it is dosed on demand: taken before an event, not accumulated over weeks like a titrated GLP-1 or testosterone protocol.

The approved product, Vyleesi, sidesteps all reconstitution: each single-use autoinjector delivers 1.75 mg in 0.3 mL, which is a fixed concentration of about 5.83 mg/mL. The label caps use at one dose per 24 hours and no more than eight doses per month. Everything harder about "how many units" only appears when you move to a compounded powder vial, where you become the pharmacist.

Approved Vyleesi vs compounded PT-141

These are the same molecule, but the packaging changes what you have to calculate.

Property	Vyleesi (FDA-approved)	Compounded PT-141
Form	Pre-filled autoinjector	Lyophilised powder in a vial
Reconstitution	None — ready to use	You add bacteriostatic water
Dose delivered	1.75 mg fixed	Whatever you draw up
Concentration	~5.83 mg/mL (1.75 mg / 0.3 mL)	Depends on water added
Approved population	Premenopausal women, HSDD	None (off-label/research)
Timing	≥45 min before activity	Not established
Max frequency	1 / 24 h, 8 / month	Not established

The right-hand column has no approved figures because compounded PT-141 has not been through the FDA review that set the left-hand ones. Any dose there is chosen by a prescriber or a research protocol, and the maths below simply tells you how many units a chosen dose becomes — it does not endorse a dose.

Reconstitution: turning a vial into units

The rule never changes. Find the concentration (mg ÷ mL of water), divide your dose by it to get the draw volume in mL, then multiply by 100 because a U-100 insulin syringe reads 100 units per 1 mL.

Worked example 1 — matching the approved dose

A 10 mg vial reconstituted with 2 mL bacteriostatic water gives 10 ÷ 2 = 5 mg/mL. To match the label's 1.75 mg dose: 1.75 ÷ 5 = 0.35 mL, × 100 = 35 units.

Draw 35 units on a U-100 syringe.

Worked example 2 — same dose, more water

Same 10 mg vial with 1 mL instead: 10 ÷ 1 = 10 mg/mL. Now 1.75 ÷ 10 = 0.175 mL, × 100 = 17.5 units.

Half the water, double the concentration, half the units — for the identical 1.75 mg dose.

Worked example 3 — a smaller trial dose

A 10 mg vial + 5 mL = 2 mg/mL. For a 0.5 mg dose: 0.5 ÷ 2 = 0.25 mL, × 100 = 25 units.

Draw 25 units on a U-100 syringe.

Worked example 4 — a 5 mg vial

A 5 mg vial + 2 mL = 2.5 mg/mL. For a 1 mg dose: 1 ÷ 2.5 = 0.4 mL, × 100 = 40 units.

Worked example 5 — reading the answer back

You drew 20 units from the 5 mg/mL mix in Example 1. Reverse it: 20 units = 0.2 mL, × 5 mg/mL = 1 mg delivered. Units-to-mg is just the same maths run backwards.

Dose-to-units reference chart

Units on a U-100 syringe for common PT-141 doses at three concentrations. Confirm every figure against your own vial label and your prescriber's instructions.

Dose	At 2 mg/mL	At 5 mg/mL	At 10 mg/mL
0.5 mg	25 units	10 units	5 units
1 mg	50 units	20 units	10 units
1.75 mg (label dose)	87.5 units	35 units	17.5 units
2 mg	100 units	40 units	20 units

At 2 mg/mL a 2 mg dose already fills an entire 1 mL syringe, so higher concentrations are used for larger draws. If your calculated volume tops 1 mL, add less water next time (or use a stronger mix).

The same dose across concentrations, visualised

One fixed 1.75 mg dose, drawn from three different mixes — the milligrams are identical, only the units on the barrel change.

How this is calculated

Every number here rests on two facts and no drug-specific constant: a U-100 syringe holds 100 units per mL, and concentration is milligrams divided by the millilitres of water you add. Dose ÷ concentration gives your draw in mL; multiply by 100 for units. The arithmetic is identical whether the vial says PT-141, BPC-157, or tirzepatide — only the numbers on your label change. The calculators on this site automate this so you can cross-check against the chart above. This is the maths behind a dose a clinician has set for you; it is not a recommendation to use PT-141.

Safety and honest caveats

Bremelanotide is approved only for premenopausal women with acquired, generalised HSDD — not for postmenopausal women, not for men, and not to enhance sexual performance. Common label effects include nausea (reported by roughly 40% of trial participants), flushing, and headache; it can cause a transient rise in blood pressure and a fall in heart rate, and repeated dosing has been linked to focal skin hyperpigmentation. Compounded PT-141 has not been evaluated by the FDA for purity, potency, or those higher off-label doses, so its risk profile is genuinely less certain. Only use any injectable under a qualified prescriber's direction.

Frequently asked questions

How many units is a 1.75 mg PT-141 dose?

It depends on the concentration. From a 5 mg/mL mix it is 35 units; from 10 mg/mL it is 17.5 units; from 2 mg/mL it is 87.5 units. The milligrams are the same — the units change with how much water you added.

How much bacteriostatic water do I add to a PT-141 vial?

There is no single correct amount — more water means a lower concentration and more units per dose, less water means the opposite. Pick a volume that keeps your intended dose to a convenient, readable number of units, and follow your prescriber or compounding pharmacy's instruction.

Is compounded PT-141 the same as Vyleesi?

It is the same molecule (bremelanotide), but Vyleesi is an FDA-approved, fixed-dose autoinjector, while compounded PT-141 is a powder you mix yourself and has not been through FDA review for dose, purity, or potency.

Is PT-141 dosed daily like other peptides?

No. It has a short half-life and is taken on demand before activity, not accumulated on a daily or weekly titration schedule. The approved product is capped at one dose per 24 hours.

Sources

This guide is for general educational purposes only and does not constitute medical advice. Always follow your prescriber’s specific instructions and consult a qualified clinician before changing any protocol.