SS-31 Reconstitution: Water, mg/mL and the Forzinity Label

SS-31 reconstitution: water for 5, 10 and 50 mg vials, the mg/mL and units each gives, set against the approved 80 mg/mL elamipretide solution and its label.

Medibact Guides · Published 2026-10-22

Illustration: A clear glass vial with pale blue liquid on a white lab bench. — Illustration

SS-31 is the one compound on this site's reconstitution list whose molecule has an approved product, and the approved product skips reconstitution entirely: FORZINITY, elamipretide for Barth syndrome, arrives as a solution at 80 mg/mL with its own preservative. That gives the research vial something no other powder here has — a regulator-reviewed benchmark for concentration, preservative strength and in-use life — and shows how far the usual water volumes sit from it. This page works the arithmetic for 5, 10 and 50 mg vials, sets it against the label, and states what the label's figures do and do not carry over (sources opened 2026-10-22). It suggests no amount and no water volume.

The label's dose, the trials and the vendor figures are on the SS-31 dosage page. Other vial and water combinations are worked by the SS-31 vial calculator; every compound is indexed on the reconstitution hub.

Water per vial and the concentration it gives

Vial	Water	Concentration	mg per U-100 unit	5 mg	10 mg	40 mg
5 mg	1 mL	5 mg/mL	0.05	100 units	—	—
5 mg	2 mL	2.5 mg/mL	0.025	200	—	—
10 mg	1 mL	10 mg/mL	0.1	50	100	—
10 mg	2 mL	5 mg/mL	0.05	100	200	—
10 mg	3 mL	3.33 mg/mL	0.033	150	300	—
50 mg	0.5 mL	100 mg/mL	1	5	10	40
50 mg	1 mL	50 mg/mL	0.5	10	20	80
50 mg	2 mL	25 mg/mL	0.25	20	40	160
50 mg	3 mL	16.7 mg/mL	0.167	30	60	240
FORZINITY (label)	—	80 mg/mL	0.8	6.25	12.5	50

One U-100 unit is 0.01 mL, and a full 100-unit syringe is 1 mL. A dash means the vial holds less than that amount. The 5 and 10 mg columns are the figures vendor pages cite for "SS-31", recorded on this site's dosage page on 2026-09-18 with no source behind them; the 40 mg column is the label's daily amount for Barth syndrome. The table shows the problem a milligram-scale compound creates that a microgram one does not: at the usual 1 to 3 mL, the vendor figures alone fill one to three syringes from a 5 or 10 mg vial. The volumes that keep a draw inside one barrel are the small ones, which the insulin syringe units page shows on 30-, 50- and 100-unit barrels.

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USP-grade, 0.9% benzyl alcohol, 30 mL multi-dose vial. Research use only.

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The approved solution as a benchmark

The label describes a product built for daily draws from one vial over about a week. Its figures, side by side with a research vial mixed in bacteriostatic water:

	FORZINITY (label)	Research vial in bacteriostatic water
Form	Ready-to-use solution	Lyophilised powder, mixed by the user
Elamipretide concentration	80 mg/mL	Whatever the water sets: 2.5 to 100 mg/mL in the table above
Preservative	Benzyl alcohol 20 mg/mL	Benzyl alcohol 9 mg/mL (0.9%), or 11 mg/mL (1.1%) in some products
Buffer and pH	Monobasic sodium phosphate; pH 4.7 to 6.1	None stated; pH not stated
Stated weight	40 mg base per 0.5 mL (46.8 mg as salt)	Usually not stated whether salt or base
In-use life	Discard 8 days after first opening, refrigerated or 20 to 25 °C	No data

Two rows matter most. The preservative strength in the approved product is about twice that of standard bacteriostatic water, chosen with the buffer for a vial that is entered daily; a powder mixed with bacteriostatic water is a different preparation, and the eight-day figure belongs to the approved one. And the salt question: the label is careful to give both 40 mg (base) and 46.8 mg (hydrochloride) per dose. A research vial that states only "50 mg" may mean either, and if it is the salt, it holds 42.7 mg of elamipretide.

How many amounts a vial holds

The water changes how each amount reads; it does not change how many amounts are in the powder.

Amount	Where it comes from	5 mg vial	10 mg vial	50 mg vial (base)	50 mg vial (salt, 42.7 mg base)
5 mg	Vendor pages, low end	1	2	10	8.5
10 mg	Vendor pages, high end	0.5	1	5	4.3
20 mg	Label, severe renal impairment	—	—	2.5	2.1
40 mg	Label, Barth syndrome, 30 kg and over	—	—	1.25	1.07

The approved vial, 280 mg, holds seven 40 mg amounts, which with the eight-day discard rule is the week the product is designed around. A 50 mg research vial holds about one. The counts are arithmetic on the vial labels and the figures; none is a course.

What the label says that transfers, and what does not

What transfers is chemistry and arithmetic: elamipretide is freely soluble in water, its molecular weight is 639.8 as the base and 749.2 as the salt, and 40 mg is a fixed number of milligrams whatever the vial. The label also states that exposure rises in proportion to dose between 2 and 80 mg a day, peaks 0.5 to 1 hour after a subcutaneous injection and is about 92% bioavailable — figures measured with the approved solution in its trial populations. What does not transfer is everything the label attaches to its own product: the dose for Barth syndrome, the storage and discard rules, and the purity and content guarantees that come with an approved vial. ClinicalTrials.gov lists 21 elamipretide studies; every registered subcutaneous trial read for this site's dosage page used the same 40 mg.

What this page does not do

It does not state an amount of SS-31, a water volume to use or a storage time for a mixed vial. It works the concentration for each volume, sets it against the approved solution, and reports what the label says. How mixed peptides are generally stored is on Medibact's how to store peptides page and the mixing steps on its how to reconstitute peptides page; Medibact's SS-31 guide covers the compound. Decisions about administering anything belong with a clinician.

Sources and dates

Opened 2026-10-22: FORZINITY (elamipretide) injection label, Stealth BioTherapeutics, effective 2025-12-10 (openFDA; DailyMed set 146bf34c-76f2-48db-ac07-fb29cce2cd75, history: version 10 published 2025-12-12), sections 2, 3, 11, 12.3 and 16; Bacteriostatic Water for Injection USP label (ProPharma Distribution, effective 2025-11-04, via openFDA), description; PubChem compound 11764719 (elamipretide, C32H49N9O5, 639.8); ClinicalTrials.gov search for elamipretide (21 studies). Vendor figures as recorded on this site's SS-31 dosage page on 2026-09-18. Concentration, unit, salt and per-vial arithmetic by this site. Corrections go to the contact page.

Bacteriostatic Water

USP-grade, 0.9% benzyl alcohol, 30 mL multi-dose vial. Research use only.

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Medibact Guides facts

The only SS-31 product with a label is not reconstituted: FORZINITY (elamipretide) is a ready-to-use solution, 280 mg in 3.5 mL (80 mg/mL), in single-patient-use vials, carton of four (label effective 2025-12-10, DailyMed set 146bf34c-76f2-48db-ac07-fb29cce2cd75, version 10 published 2025-12-12, read via openFDA 2026-10-22).
Each 0.5 mL of the approved solution holds 40 mg of elamipretide (46.8 mg as the hydrochloride salt), 10 mg of benzyl alcohol and 2.07 mg of monobasic sodium phosphate, at pH 4.7 to 6.1. That is 20 mg/mL of benzyl alcohol, about twice the 9 mg/mL (0.9%) in standard bacteriostatic water, whose labels also list an 11 mg/mL (1.1%) version (FORZINITY label; Bacteriostatic Water for Injection USP label, effective 2025-11-04).
The label calls elamipretide hydrochloride 'freely soluble in water' and gives its molecular weight as 749.2; the base is 639.8 (PubChem CID 11764719, read 2026-10-22). The base is 85.4% of the salt, so a vial labelled 50 mg of the salt holds 42.7 mg of elamipretide, and one labelled 10 mg holds 8.5 mg (arithmetic by this site).
Research vials are sold as 5, 10 and 50 mg. In 1 mL of water they give 5, 10 and 50 mg/mL; in 2 mL, 2.5, 5 and 25 mg/mL. Matching the label's 80 mg/mL from a 50 mg vial would need 0.625 mL of water (arithmetic by this site).
The label stores unopened vials at 2 to 8 °C, not frozen, and after the first dose allows the opened vial either refrigerated or at 20 to 25 °C, with the instruction to discard it 8 days after first opening. That is a statement about the approved solution with its preservative and buffer; no stability data exist for a research vial reconstituted in bacteriostatic water.
The label's 40 mg daily amount is 0.5 mL (50 U-100 units) of the 80 mg/mL product, 80 units at 50 mg/mL, and 160 units at 25 mg/mL; it cannot be drawn from a 5 mg or 10 mg vial, which holds less than one such amount (arithmetic by this site).
ClinicalTrials.gov returned 21 studies for elamipretide on 2026-10-22. The label states that exposure rises in proportion to the dose between 2 and 80 mg a day under the skin, with peak levels 0.5 to 1 hour after injection and about 92% bioavailability.

Frequently asked questions

How much bacteriostatic water goes in a 10 mg SS-31 vial?

No label sets it, because the approved elamipretide product is a ready-made solution. The arithmetic: 1 mL gives 10 mg/mL (0.1 mg per U-100 unit), 2 mL gives 5 mg/mL (0.05 mg per unit) and 3 mL gives 3.33 mg/mL. In 2 mL, 5 mg is 100 units, one full 1 mL syringe; vendor figures of 5 to 10 mg therefore fill one or two syringes at that volume.

What concentration is Forzinity?

80 mg/mL: 280 mg of elamipretide in 3.5 mL. The labelled 40 mg is 0.5 mL, or 50 units on a U-100 syringe. Reaching that strength from a research vial would mean 50 mg in 0.625 mL of water; the usual volumes give weaker solutions.

How many units is 40 mg of SS-31 from a 50 mg vial?

40 units in 0.5 mL of water (100 mg/mL), 80 units in 1 mL (50 mg/mL), 160 units in 2 mL (25 mg/mL) and 240 units in 3 mL. If the vial's 50 mg is the hydrochloride salt, it holds 42.7 mg of elamipretide base, which is one 40 mg amount with 2.7 mg left over.

How long does reconstituted SS-31 last?

Nothing has measured it for a research vial. The approved solution, which contains 20 mg/mL benzyl alcohol and a phosphate buffer, is discarded 8 days after first opening, refrigerated or at room temperature. A powder mixed with bacteriostatic water is a different preparation and the label's figure does not transfer to it.

Does the salt form matter for SS-31?

For a milligram-scale compound it does. Elamipretide is supplied as a hydrochloride salt; the label's 40 mg dose is 46.8 mg of salt. A research vial that does not say whether its stated weight is salt or base can differ from the label's figure by about 15%, which is larger than the effect of most water-volume choices on how a dose reads.