Selank Reconstitution: Water per 5 mg and 10 mg Vial

How much bacteriostatic water a 5 mg or 10 mg Selank vial takes, the concentration each volume gives, and what reproduces the registered 1.5 mg/mL solution.

Medibact Guides · Published 2026-09-19

Illustration: A glass vial of white lyophilized powder on a white bench, softly lit. — Illustration

Selank is a synthetic heptapeptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, sold on the research market as a lyophilized powder in 5 mg and 10 mg vials. Reconstituting it raises a question most compounds do not: the only registered Selank product in the world is a ready-made nasal solution of a stated strength, so there is a documented concentration to compare a reconstituted vial against, and the arithmetic that gets there is one division. This page reports the water volumes, the concentration each gives, the volume that matches the registered solution, and what an actuation of a metered nasal pump would hold at each concentration. It reports and does not recommend, and it does not describe how to fill any device.

The Selank calculator runs the same sums for any vial and volume; the sourced figures and their provenance are on the Selank dosage page, and every compound's arithmetic is indexed on the reconstitution hub.

Water per vial and the concentration it gives

One U-100 unit is a hundredth of a millilitre (MedlinePlus, "Giving an insulin injection", reviewed 2024-07-21). The two rows in bold are not calculator presets; they are the volumes that produce the strength of the registered Russian nasal solution, 1.5 mg/mL.

Vial	Water added	Concentration	Micrograms per unit
5 mg	1 mL	5,000 mcg/mL	50
5 mg	2 mL	2,500 mcg/mL	25
5 mg	3 mL	1,667 mcg/mL	16.7
5 mg	3.33 mL	1,500 mcg/mL	15
10 mg	1 mL	10,000 mcg/mL	100
10 mg	2 mL	5,000 mcg/mL	50
10 mg	3 mL	3,333 mcg/mL	33.3
10 mg	6.67 mL	1,500 mcg/mL	15

A 10 mg vial in 1 mL and a 5 mg vial in 2 mL differ by a factor of four in concentration, which is the whole reason a unit figure quoted without its vial and volume means nothing. The 6.67 mL row carries a practical caveat that belongs with it rather than in a footnote: many research vials are not built to hold that much liquid, and a volume that does not fit the vial is not an option however clean the arithmetic is.

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The registered solution as a reference point

Most compounds on this site have no manufactured product to compare a reconstituted vial against. Selank does. The registered Russian product is 0.15% nasal drops — 1.5 mg per mL, 4.5 mg in a 3 mL bottle — and the division is straightforward: the milligrams in the vial divided by 1.5 gives the millilitres of water that reproduce that strength. Five milligrams needs 3.33 mL; ten needs 6.67.

What that match does and does not establish is worth being exact about. It establishes the concentration, and therefore the micrograms in any measured volume. It does not establish the preservative system, the sterility assurance, the pH or the excipients of a manufactured nasal product, and it does not make a reconstituted vial into that product. The registered solution is also, on its own label, stored at or below 25 degrees Celsius protected from light with a two-year shelf life as supplied — terms set for a preserved manufactured solution, not for a vial mixed at a bench, for which no label exists anywhere.

Micrograms per spray, if the solution goes into a metered pump

A recurring question about the micrograms-dosed nasal peptides is what a reconstituted vial would deliver per spray rather than per syringe unit. The answer rests on one figure — the volume a metered pump delivers per actuation — and two approved labels state it for peptide products. A desmopressin nasal spray label gives 10 mcg in 0.1 mL per spray, with a 5 mL bottle delivering 50 sprays, which is 0.1 mL of solution per actuation on the bottle's own arithmetic. The SYNAREL label for nafarelin states that after priming, each actuation delivers approximately 100 microlitres containing approximately 200 mcg of nafarelin base, from a 2 mg/mL solution — the same 0.1 mL, and 2,000 mcg/mL divided by ten gives exactly the 200 mcg the label states.

So an actuation is ten U-100 units of liquid, and micrograms per spray is the concentration in mcg/mL divided by ten.

Concentration	Per U-100 unit	Per 0.1 mL actuation	Actuations in a 5 mg vial	Actuations in a 10 mg vial
1,500 mcg/mL	15 mcg	150 mcg	33	66
1,667 mcg/mL	16.7 mcg	167 mcg	30	60
2,500 mcg/mL	25 mcg	250 mcg	20	40
3,333 mcg/mL	33.3 mcg	333 mcg	15	30
5,000 mcg/mL	50 mcg	500 mcg	10	20
10,000 mcg/mL	100 mcg	1,000 mcg	5	10

The number of actuations is set by the water volume, not by the vial: a 5 mg vial in 3.33 mL holds 33 sprays of 150 mcg, and the same vial in 1 mL holds 5 sprays of 500 mcg. The milligrams in the vial are the same in both.

These figures carry one assumption that should travel with them: they adopt the 0.1 mL actuation volume stated on the two labels above rather than any measurement of a particular pump. A device that delivers a different volume moves every number in the last two columns proportionally, and nothing here describes filling, priming or using such a device.

Why a drop and a spray of the same solution differ

The Russian label doses in drops from a dropper cap, and this site's Selank dosage page works that regimen out at the conventional 20 drops per millilitre: one drop of 1.5 mg/mL solution is 0.05 mL and 75 mcg. A metered pump actuation of the same solution is 0.1 mL and 150 mcg. Matching the registered concentration therefore does not match the registered dose — the delivery device doubles it. This is the same class of error as quoting a syringe-unit figure without its concentration, one step further along: with micrograms-dosed compounds, the volume of the delivery step matters as much as the strength of the solution.

The mixing steps, as a label describes them

Selank's own registered product is a solution and is never reconstituted, so the labelled procedure reported here is the general one for a lyophilized peptide supplied with bacteriostatic water, from the EGRIFTA WR (tesamorelin) prescribing information revised 3/2025: the stated volume of Bacteriostatic Water for Injection is added to the vial; the vial is moved in a circle to mix the powder and liquid and is not shaken; the solution is inspected and not used if particles appear or it is cloudy or coloured. The full step-by-step procedure for any lyophilized vial is on Medibact's how to reconstitute peptides page and is not repeated here; what labels and manufacturers state about storing a reconstituted vial is on Medibact's how to store peptides page.

What this page does not do

It does not state an amount of Selank to use, a route, a frequency or a course, and it does not describe how to assemble or operate a nasal spray. It converts vial sizes and water volumes into concentrations, syringe units and per-actuation amounts, states the assumption behind the actuation figure, and names the one concentration with a registered product behind it. The compound itself — mechanism, evidence, sourcing — is covered in Medibact's Selank guide; the same micrograms-per-unit problem in a larger vial is worked on the Semax reconstitution page. Decisions about administering anything to a person belong with a clinician.

Sources and dates

Opened 2026-09-19: the DailyMed structured product labels for desmopressin acetate nasal spray (Apotex Corp.) and SYNAREL (nafarelin acetate) nasal solution (Pfizer), dosage forms and how-supplied sections read for the per-actuation volume; the EGRIFTA WR prescribing information (revised 3/2025, section 2.2) for the labelled mixing steps; MedlinePlus, "Giving an insulin injection" (reviewed 2024-07-21). Opened 2026-09-18 and carried from the Selank dosage page: the Russian register entry and instruction for Selank 0.15% nasal drops on rlsnet.ru, for the 1.5 mg/mL strength, the 3 mL bottle and the storage terms. Vial sizes are the ones the calculator preset uses. Corrections go to the contact page.

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Medibact Guides facts

Selank research vials are 5 mg and 10 mg, the two sizes this site's calculator is preset to; the only registered Selank product is not a vial at all but a Russian nasal solution, 0.15%, 1.5 mg per mL in a 3 mL bottle (register entry on rlsnet.ru, read 2026-09-18).
Reproducing the registered product's concentration from a research vial is one division: 5 mg divided by 1.5 mg/mL is 3.33 mL of bacteriostatic water, and 10 mg divided by 1.5 mg/mL is 6.67 mL (arithmetic, this page). Neither volume is among the 1, 2 and 3 mL the calculator presets, and neither appears on vendor pages.
At the calculator's volumes a 5 mg vial gives 5,000, 2,500 and 1,667 mcg/mL in 1, 2 and 3 mL, and a 10 mg vial gives 10,000, 5,000 and 3,333 mcg/mL — so one U-100 unit holds 50, 25 and 16.7 mcg from the 5 mg vial and 100, 50 and 33.3 mcg from the 10 mg vial.
Metered nasal pumps for peptide products deliver about 0.1 mL per actuation, which is ten times a U-100 unit: a desmopressin nasal spray label states 10 mcg in 0.1 mL per spray from a 5 mL bottle delivering 50 sprays, and the SYNAREL (nafarelin) label states that each actuation delivers approximately 100 microlitres containing approximately 200 mcg of nafarelin base from a 2 mg/mL solution (both labels read on DailyMed, 2026-09-19).
Because an actuation is 0.1 mL, micrograms per spray is the concentration in mcg/mL divided by ten: a 5 mg vial in 3.33 mL, the 1.5 mg/mL solution, gives 150 mcg per spray and about 33 sprays; a 10 mg vial in 6.67 mL gives the same 150 mcg per spray and about 66 sprays (arithmetic, this page).
A metered spray of the registered concentration delivers twice what the registered product's dropper does. The Russian label doses in drops, and at the conventional 20 drops per millilitre one drop of 1.5 mg/mL solution is 75 mcg, against 150 mcg for a 0.1 mL actuation of the same solution — the difference is the delivery device, not the strength.
No label anywhere covers a reconstituted Selank vial, because the registered product is a ready-made solution; the labelled mixing procedure reported here is the one for a lyophilized peptide supplied with bacteriostatic water, from the EGRIFTA WR prescribing information revised 3/2025: the stated volume is added, the vial is moved in a circle rather than shaken, and the solution is inspected and not used if cloudy, coloured or containing particles.
The registered solution's own storage terms are 25 degrees Celsius or below, protected from light, with a two-year shelf life for the unopened product (rlsnet.ru, read 2026-09-18) — terms that describe a manufactured, preserved solution rather than a vial reconstituted at a bench.

Frequently asked questions

How much bacteriostatic water goes into a 5 mg Selank vial?

No label sets it, because no Selank vial has a label. The calculator's presets are 1, 2 and 3 mL, which give 5,000, 2,500 and 1,667 mcg/mL. One volume has a documented reference point: 3.33 mL produces 1.5 mg/mL, the concentration of the registered Russian nasal solution. The volume decides only how many micrograms sit in each syringe unit or each spray; the 5 mg in the vial does not change.

What concentration does a 10 mg Selank vial give?

10 mg/mL in 1 mL, 5 mg/mL in 2 mL and 3.33 mg/mL in 3 mL — that is 10,000, 5,000 and 3,333 mcg per millilitre, or 100, 50 and 33.3 mcg per U-100 unit. To reach the registered product's 1.5 mg/mL the 10 mg vial needs 6.67 mL, which is more water than many vials are designed to hold and is worth checking against the vial's stated capacity before it is planned around.

How many micrograms are in one spray if a reconstituted vial is put in a nasal pump?

The concentration divided by ten, because a metered peptide nasal pump delivers about 0.1 mL per actuation — 10 mcg in 0.1 mL on a desmopressin label, and approximately 100 microlitres per actuation on the SYNAREL label. So 1,500 mcg/mL gives 150 mcg a spray, 2,500 mcg/mL gives 250, and 5,000 mcg/mL gives 500. This page states the arithmetic only; it does not describe how to fill or prime a spray device, and the figures assume an actuation volume matching those labels rather than a measured one.

Is Selank reconstituted differently from other peptides?

The procedure is the same as for any lyophilized peptide; what differs is the amount of water that makes sense. Selank amounts are micrograms, so a small water volume puts an ordinary draw at a few units, where a half-unit reading error is a large fraction of it. More water gives a lower concentration, larger and more readable draws, and — at 3.33 mL for a 5 mg vial — a solution matching the only registered Selank product's strength.

How many sprays or doses does a Selank vial hold?

At 0.1 mL an actuation, a 5 mg vial reconstituted to 3.33 mL holds about 33 sprays and a 10 mg vial at 6.67 mL about 66, both at 150 mcg a spray. Measured as syringe draws instead, a 5 mg vial holds about sixteen 300 mcg amounts or ten 500 mcg amounts, at any concentration — the concentration changes the units drawn, never the number of amounts a vial contains, which is set by the milligrams alone.

Can the Russian label's drop figures be used with a reconstituted vial?

The strengths can be matched; the delivery cannot. A 5 mg vial in 3.33 mL is the same 1.5 mg/mL solution the label describes, but the label's doses are counted in drops from a dropper cap, and a drop at the conventional 20 per millilitre is 0.05 mL, half a metered spray. The same solution therefore delivers 75 mcg from a dropper and 150 mcg from a 0.1 mL pump. A reconstituted research vial also lacks the registered product's preservative system and its manufacturing controls, so matching a concentration does not reproduce a product.