What is the SS-31 dosage?

The only approved dose is FORZINITY's: 40 mg subcutaneously once daily for patients with Barth syndrome weighing at least 30 kg, or 20 mg once daily in adults with an eGFR below 30 mL/min who are not on dialysis. That is a label dose for one rare disease. There is no approved dose for any other use, and the large trial in mitochondrial myopathy used the same 40 mg daily without meeting its endpoints.

Is SS-31 FDA approved?

Yes, as elamipretide under the brand FORZINITY, which received accelerated approval on 19 September 2025 for Barth syndrome only. Accelerated approval requires a confirmatory trial. “SS-31 peptide” powder sold online is not the approved product, and it has no FDA approval for anti-ageing, energy or any other use.

What are the benefits of SS-31?

The one benefit the FDA has accepted is improved muscle strength in Barth syndrome, on an intermediate endpoint, pending confirmation. Its randomized trials elsewhere were negative: MMPOWER-3 in mitochondrial myopathy missed both primary endpoints, and EMBRACE STEMI found no reduction in heart-attack infarct size. Claims of general mitochondrial, longevity or performance benefits are not supported by those trials.

How many units is 40 mg of SS-31?

In FORZINITY at 80 mg/mL, 40 mg is 0.5 mL, which is 50 units on a U-100 syringe. For a powder vial the answer depends on the water you add: a 50 mg vial in 1 mL is 50 mg/mL, so 40 mg is 0.8 mL or 80 units; the same vial in 2 mL would put 40 mg at 1.6 mL, more than an insulin syringe holds.

How long does SS-31 last after opening?

For FORZINITY, 8 days after first opening, refrigerated or at room temperature (20°C to 25°C). That figure is stability data for the approved, preserved solution. A powder vial reconstituted at home has no published in-use period.

SS-31 Dosage Calculator — Elamipretide (Forzinity) Label Dose

Approved in September 2025 as FORZINITY, for muscle strength in Barth syndrome only — supplied as a ready-made solution, not a powder.

Written by Kashif Khan, who builds and maintains this site and is not a clinician. Every figure links to its primary source.

Approved

FDA-approved for Barth syndrome only (accelerated approval)

The FDA granted accelerated approval on 19 September 2025 to FORZINITY (elamipretide) injection, to improve muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg. Accelerated approval is conditional: a confirmatory placebo-controlled trial is required. The approved product is an 80 mg/mL solution in a multi-dose vial — nothing to reconstitute. “SS-31” sold online as a powder is not that product, and every other use is unapproved.

Calculator inputs

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Enter the label, dilution and dose. The result updates as you type.

Syringe volume

SS-31 (elamipretide) in the vial

FORZINITY is already a solution: 80 mg/mL, so 40 mg is 0.5 mL

Bacteriostatic water to add

Dose per injection

More optionsReverse calculation, schedule and cost

Enter the bacteriostatic water you added and get the volume to draw.

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40units(0.4 mL)

Concentration: 50 mg/mL
Water added: 1 mL
Doses in vial: 2

How the concentration is calculated

This divides the peptide by the water you add. The powder occupies a little volume of its own, which is negligible on a typical vial but not on one with a heavy bulking agent. When a product label states a concentration, use the label’s number.

Key facts

Molecular weight: 749.2 DaAs the trihydrochloride salt, C32H49N9O5·3HCl, which is the form the label states. Sequence D-Arg-2′,6′-dimethyl-Tyr-Lys-Phe-NH2.
Half-life: Not published. No accessible human pharmacokinetic study reports one, so any specific figure quoted elsewhere has no primary source behind it.
Also sold as: elamipretide, Forzinity, MTP-131, Bendavia

How good is the evidence?

Approved on an intermediate endpoint after the randomized trials missed their primary endpoints. In the label's 12-week placebo-controlled crossover (12 patients with Barth syndrome) elamipretide was not superior to placebo on the 6-minute walk test or fatigue; the muscle-strength signal behind the approval came from the open-label extension. In primary mitochondrial myopathy, the 218-patient MMPOWER-3 trial missed both primary endpoints.

What FORZINITY's label actually approves

One dose for one condition. The label dose is 40 mg (0.5 mL of the 80 mg/mL solution) injected subcutaneously once daily, for patients with Barth syndrome weighing at least 30 kg. It is a fixed dose, not weight-based. Adults with an eGFR below 30 mL/min who are not on dialysis take 20 mg once daily; the label gives no recommendation for patients on dialysis or for children with renal impairment.

The product is a clear solution in a 280 mg/3.5 mL vial, injected into the abdomen at least 2 inches from the navel or the outer thigh, rotating sites daily. It is labelled for subcutaneous use only — not intravenous. On a U-100 syringe the 40 mg dose is 50 units and the 20 mg dose is 25 units, because the label concentration fixes the volume.

The trials, including the ones that failed

The approval is unusual and worth reading accurately. In TAZPOWER, the label's placebo-controlled crossover, 12 patients with Barth syndrome received 40 mg daily or placebo for 12 weeks each; elamipretide was not superior to placebo on its primary endpoints of 6-minute walk distance and fatigue. The FDA approved it on knee-extensor muscle strength, an intermediate endpoint, from the open-label extension — and required a confirmatory randomized trial.

Outside Barth syndrome, the large trials were negative. MMPOWER-3 randomized 218 adults with primary mitochondrial myopathy to 40 mg daily subcutaneously or placebo for 24 weeks and missed both primary endpoints. In EMBRACE STEMI, an intravenous infusion of 0.05 mg/kg/h around reperfusion did not reduce infarct size. None of these supports the general “mitochondrial” benefits SS-31 is sold on.

Injection-site reactions are the norm, not the exception

In the label's placebo-controlled period, injection-site erythema occurred in 100% of patients on elamipretide against 25% on placebo, pain in 75% against 42%, induration in 67% against 17%, pruritus in 67% against 17%, and bruising and urticaria in 25% each against none. The label also warns of hypersensitivity reactions, including serious ones, and of benzyl alcohol toxicity in neonates from the preservative.

How long an opened vial lasts

Unopened vials are refrigerated at 2°C to 8°C and never frozen. Once opened, a vial may be kept refrigerated or at 20°C to 25°C and must be discarded 8 days after first opening. That 8-day window belongs to this formulation, preserved with benzyl alcohol; it says nothing about a powder reconstituted from an online vial, which has no stability data at all.

Common questions

Sources

Every number on this page comes from one of the documents below. Where no reliable source exists, the page says so instead of filling the gap.

FDA labelFDA / DailyMed· 2025-12
FORZINITY (elamipretide) injection — FDA prescribing information
RegulatorFDA· 2025-09-19
FDA Grants Accelerated Approval for First Treatment of Barth Syndrome
Published studyGenetics in Medicine· 2021
Thompson WR et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome. Genet Med 2021
Published studyNeurology· 2023
Karaa A et al. Efficacy and safety of elamipretide in individuals with primary mitochondrial myopathy: the MMPOWER-3 trial. Neurology 2023
Published studyEuropean Heart Journal· 2016
Gibson CM et al. EMBRACE STEMI study: a Phase 2a trial of intravenous MTP-131 on reperfusion injury in patients undergoing primary PCI. Eur Heart J 2016