Vial duration

PT-141 vial duration calculator

Estimate how many weeks one 10 mg PT-141 vial covers at your dose and weekly cadence.

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Last updated: May 13, 2026

Vial (mg)

Dose (mg)

Doses / week

Total doses

Lasts

2.5 weeks

PT-141 weeks-of-supply at common cadences

How long one 10 mg PT-141 vial covers at a 1.75 mg per dose, for three weekly cadences. Total doses per vial: 5.

Doses per week	Total doses per vial	Weeks of supply
1	5	5.0
2	5	2.5
3	5	1.7

Math weeks-of-supply assumes every dose draws cleanly. Stability typically caps a reconstituted vial at 4–6 weeks of refrigerated use regardless of how much liquid remains.

Worked example

How long one PT-141 vial lasts, the long version

Total doses in the vial: floor(10 ÷ 1.75) = 5. The floor matters — a partial dose at the bottom doesn't count.
Cadence: 2 doses per week for PT-141 at this example step.
Math weeks-of-supply: 5 ÷ 2 = 2.5 weeks of liquid in the vial.
Stability ceiling: most reconstituted peptides are typically used within 4–6 weeks of refrigerated storage. Whichever number is smaller is the one that binds your refill date.
Doubling the dose roughly halves both numbers — and titration usually closes the gap between "math weeks" and "stability weeks" without you noticing.

Scenarios people actually run into

Three things that come up logging PT-141

Math says one 10 mg PT-141 vial covers 2.5 weeks at 1.75 mg per dose. Stability typically caps a reconstituted vial at 4–6 weeks. Whichever number is smaller is the date on your refill calendar.
Titration up doubles the dose and halves the vial. A 12-week-on-paper vial becomes a 6-week vial the day you step up — order the next vial the same day you take the step.
Shipping windows are the silent third constraint. If your supplier runs 1–3 weeks, the refill order has to leave at least that long before "math weeks" or "stability weeks," whichever is binding.

Same-category neighbor

PT-141 next to Semax

Both sit in the Sexual health bucket — here's the vial duration math side by side on each one's example vial.

	PT-141	Semax
Vial	10 mg	5 mg
Cadence	2/wk	7/wk
Weeks of supply	2.5	1.7

Want the full breakdown? Semax reference →

PT-141, also known as Bremelanotide, is a synthetic peptide that people use for its effects on sexual arousal. It was developed from a research chemical called Melanotan II but was designed to have more targeted effects on libido. Unlike other substances that work on blood flow, PT-141 is reported to work on the brain to increase sexual desire in both men and women. This page covers what PT-141 is, how people use it, and the common ways it is tracked in Peptide Pilot.

Planning PT-141 vials in real life

PT-141 is the only peptide on this site dosed on demand rather than on a schedule, and that changes vial planning completely. A 10 mg vial covers 5 doses at 1.75 mg mathematically — but actual usage might spread those 5 doses over 1 week, 4 weeks, or 8 weeks depending on cadence. The math is the easy part; the calendar is harder.

Stability is the binding constraint for any on-demand peptide. The reconstituted vial caps at 4-6 weeks of refrigerated usability. If you're using PT-141 less than once a week, you'll discard partial vials regardless of dose-count math. The fix many users settle on: smaller 5 mg vials reconstituted with 1 mL of water, finished in ~3 doses inside stability.

Storage and shelf life for PT-141

Proper storage is essential for making sure your PT-141 remains effective. Before it’s mixed, the lyophilized (freeze-dried) powder is quite stable. For long-term storage, it should be kept in the freezer, where it can remain potent for a year or even longer. For shorter-term storage, keeping it in a refrigerator is also perfectly fine. The key is to keep it away from heat and light, as both can degrade the delicate peptide molecules over time. So, when your vial of powder first arrives, the best practice is to pop it right into the fridge or freezer until you are ready to reconstitute it.

Once you’ve reconstituted the PT-141 by mixing it with bacteriostatic water, the rules of storage change. The liquid solution is much less stable than the powder and must be kept refrigerated at all times. Do not freeze the mixed solution, as the freeze-thaw cycles can damage the peptide. When kept in the fridge, a reconstituted vial of PT-141 is typically good for about 30 to 60 days. After that, its potency may begin to decline. As a conservative habit, it’s worth writing the date you mixed it directly on the vial. This way, you can easily keep track of its age and ensure you are always using a fresh solution.

How the PT-141 vial duration calculator works

A 10 mg PT-141 vial mathematically covers ~5 doses at 1.75 mg — but the on-demand cadence usually means stability runs out before doses do. At twice-weekly use the vial empties inside stability; at less frequent use, plan to discard.

The formula is two divisions. Total doses per vial equals vial mg divided by dose mg, rounded down. Weeks of supply equals total doses divided by doses per week. With a 10 mg vial of PT-141, a 1.75 mg dose, and 2 dose per week, the vial covers 5 doses, or about 2.5 weeks of supply.

The three inputs that move the answer: vial mg (set when you bought the vial), dose mg (set by your protocol step), and doses-per-week (set by the peptide's half-life). Once a vial is reconstituted it also has a stability ceiling — most lyophilized peptides reconstituted in BAC water are typically used within four to six weeks of refrigerated storage, so a vial that mathematically lasts twelve weeks may not last twelve weeks in practice.

One of the most practical questions when starting with a new peptide is, "How long will this vial last me?" This calculator is designed to answer exactly that. By looking at the total amount of PT-141 in your vial and the size of your intended dose, it can give you a clear estimate of your supply. This is especially helpful for a peptide like PT-141, where your usage isn't on a fixed daily schedule. It helps you plan ahead so you know when you might need to reorder, ensuring your research can continue uninterrupted.

Let's use our common example to see how it works. You have a 10mg vial of PT-141. You've gone through the process of finding your ideal dose and settled on 1.75mg per use. To find out how many doses are in your vial, you simply divide the total amount in the vial by your dose size. So, 10mg divided by 1.75mg equals approximately 5.7. This means you can get 5 full doses from the vial, with a little bit left over. If you plan to use it about twice a week, as the example suggests, that single 10mg vial would last you about two and a half weeks.

This calculation is also incredibly useful for understanding how dose changes affect your supply. If you find that a smaller 1mg dose works well for you, that same 10mg vial would suddenly yield 10 doses, potentially lasting you five weeks if used twice a week. On the other hand, if you need a higher dose, the vial will be used up more quickly. This calculator lets you play with these numbers. It provides a tangible, financial reason to find the minimum effective dose for your body, helping you be both Ecient and economical in your tracking journey.

Common PT-141 vial-planning mistakes

Storing the mixed vial at room temperature instead of in the refrigerator.

Frequently asked questions about PT-141 vial duration

How does the PT-141 vial duration calculator estimate weeks of supply?

It floors total doses (vial mg ÷ dose mg) then divides by doses per week. For this PT-141 example — a 10 mg vial, 1.75 mg per dose, 2 dose/week — that's floor(10 ÷ 1.75) ÷ 2 = about 2.5 weeks. Flooring matters: a partial dose left in the vial doesn't count. On-demand PT-141 use makes vial planning calendar-bound, not dose-count-bound.

Should I plan refills around the math, or around stability?

Whichever runs out first. Math says PT-141 at the example dose lasts the calendar weeks shown above. Stability says most reconstituted peptides are typically used within 4–6 weeks of refrigerated storage regardless of how much liquid is left. If the math says 12 weeks but stability caps at 5, plan around 5 — and reconstitute the next vial with less water so you finish it in the stability window. On-demand PT-141 use makes vial planning calendar-bound, not dose-count-bound.

Does titrating the PT-141 dose up shorten vial life?

Yes, often dramatically. Doubling the dose halves the doses-per-vial. The calculator shows real-time how a step-up changes the weeks-of-supply line, so you can re-time refill orders before a titration event rather than discovering the gap mid-protocol. On-demand PT-141 use makes vial planning calendar-bound, not dose-count-bound.

What if I take PT-141 less often than the default cadence here?

Drop the doses-per-week field. With 2 dose/week the example vial lasts about 2.5 weeks; halving the cadence roughly doubles that, but you'll hit the stability ceiling first. A vial that mathematically covers 16 weeks rarely covers 16 weeks in practice. On-demand PT-141 use makes vial planning calendar-bound, not dose-count-bound.

Related on Peptide Pilot

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