SS-31 50 mg vial dosage

What SS-31 is

Class:

Mitochondria-targeted tetrapeptide

Also called:

Elamipretide, MTP-131, Bendavia

Used for:

FDA-approved (accelerated approval, 2025) as Forzinity to improve muscle strength in Barth syndrome, a rare genetic mitochondrial disease. Sold online as a longevity and cellular-energy peptide.

Human evidence:

Moderate human evidence. Sixteen randomised trials, all in diagnosed patients: primary mitochondrial myopathy through dose-escalation and crossover designs to a large controlled study, plus Barth syndrome and a topical ophthalmic formulation. The lead trial in primary mitochondrial myopathy did not meet its primary endpoints. In Barth syndrome, FDA granted accelerated approval in September 2025 on an improvement in knee extensor muscle strength, an intermediate endpoint, with continued approval contingent on a confirmatory trial. No trial has studied healthy adults.

US status:

FDA-approved · prescription only. FDA granted accelerated approval on 19 September 2025 to Forzinity (elamipretide), NDA 215244 held by Stealth BioTherapeutics, to improve muscle strength in adult and paediatric patients with Barth syndrome weighing at least 30 kg, at 40 mg subcutaneously once daily (20 mg in adults with eGFR below 30 mL/min not on dialysis). Continued approval may depend on a confirmatory trial. That approval covers Barth syndrome only: it does not extend to energy, longevity or any use in healthy adults, and research-chemical vials sold as SS-31 are not the approved product and carry none of its quality control.

The full picture, with every study: SS-31 guide.

How to mix a 50 mg SS-31 vial

For this vial: 1 mL of bacteriostatic water makes 50 mg/mL, so 40 mg is 80 units (0.8 mL) on a U-100 insulin syringe. Pick a different volume from the units table if you want bigger or smaller draws; the number of doses stays the same.

1. Wipe the rubber stoppers of both the peptide vial and the bacteriostatic water vial with an alcohol swab and let the alcohol dry. ^[3][4]
2. With a new sterile needle and syringe, draw up the amount of bacteriostatic water you have chosen for the dilution. ^[3][4][5]
3. Inject the water into the peptide vial by aiming the stream against the inside glass wall, which helps prevent foaming. ^[6]
4. Swirl or roll the vial gently until the powder has fully dissolved; do not shake it. Do not inject the solution if it is cloudy or has particles in it. ^[3][4][6]
5. Label the vial with the date and time it was mixed, the amount of water added and how long it can be used after mixing. ^[3]
6. Store the mixed vial in the refrigerator at 2-8°C (36-46°F) and do not freeze it. ^[6]

Step by step with pictures: how to reconstitute peptides. About the water itself: bacteriostatic water.

Storing SS-31 vials

• Freeze-dried (lyophilized) peptide keeps far longer than peptide in solution; peptide suppliers advise storing the powder at -20°C away from bright light. ^[7]
• Protect peptide vials from heat and light. ^[7][8]
• Avoid repeated freeze-thaw cycles; a prescription peptide label also says not to freeze a vial once it has been mixed. ^[6][7]
• Once a multi-dose vial, such as bacteriostatic water, has been opened (needle-punctured), date it and discard it within 28 days unless its manufacturer states another date. ^[9][10]

More detail: peptide storage and shelf life.

Injecting safely

• Clean the injection site with an alcohol swab and let the skin dry completely before injecting. ^[11][12]
• Pinch up a fold of skin and fat (not muscle) and insert the needle at a 45- to 90-degree angle: 90 degrees where there is enough fatty tissue, 45 degrees where there is little. ^[11][12][13]
• Pulling back on the plunger (aspiration) is not necessary for a subcutaneous injection, because the chance of the needle being in a blood vessel is small. ^[11]
• Inject slowly, at roughly 10 seconds per mL. ^[11]
• Common sites are the belly, the thigh and the upper arm; rotate sites, keeping each injection at least 1 inch (2.5 cm) from the last. ^[6][11][12]

Hygiene and warning signs

• Use a new sterile needle and syringe for every injection and every time you enter a vial; never reuse them. ^[5][9][12]
• Never share needles, syringes or pens with anyone, even if the needle is changed; unsafe injection practices spread hepatitis B, hepatitis C and HIV. ^[5][8][9]
• Put used needles and syringes in a sharps disposal container straight away (FDA-cleared if possible), never loose in the trash, recycling or toilet, and dispose of the container following your community's guidelines. ^[14][15]
• Contact a health care provider if the injection site shows signs of infection, such as redness, swelling, red streaks or a fever. ^[12]

Where to inject: subcutaneous injection sites.

How SS-31 works

• SS-31 is elamipretide, a four-residue peptide (D-arginine, 2,6-dimethyltyrosine, lysine and phenylalaninamide). The FDA-approved label describes it as a mitochondrial cardiolipin binder that localises to the inner mitochondrial membrane and improves mitochondrial structure and function. ^[16]
• The laboratory basis for that description: a fluorescent analogue of SS-31 bound cardiolipin, the phospholipid the cristae of the inner membrane depend on, with high affinity, and the resulting complex blocked cytochrome c peroxidase activity. Pretreating rats protected cristae during kidney ischaemia, prevented mitochondrial swelling and let ATP recover faster after blood flow returned. ^[17]
• The label's pharmacokinetics come from the approved injectable product: peak concentrations 0.5 to 1 hour after a subcutaneous injection, absolute bioavailability around 92%, distribution through total body water, low plasma protein binding of about 39%, breakdown by stepwise trimming from the C-terminus into two inactive fragments, and essentially the whole dose recovered in urine within 48 hours in people with normal kidney function. ^[16]

What the SS-31 research found

Human evidence: moderate human evidence. Each result says what was studied.

• Human studyIn the first randomised trial, 36 adults with genetically confirmed primary mitochondrial myopathy received intravenous elamipretide at escalating levels or placebo over two hours. Those on the highest level walked a mean of 64.5 metres further at day 5 against 20.4 metres for placebo (p = 0.053), with a dose-dependent increase across the groups (p = 0.014) and no significant differences on the other efficacy or safety measures. ^[18]
• Human studyA randomised crossover trial in 30 people with the same diagnosis, four weeks on subcutaneous elamipretide and four weeks on placebo, missed its primary endpoint: the difference in six-minute walk distance was 19.8 metres (95% CI -2.8 to 42.5, p = 0.0833). Patient-reported fatigue scores did improve on treatment. ^[19]
• Human studyThe largest trial, MMPOWER-3, randomised 218 adults with primary mitochondrial myopathy to 24 weeks of 40 mg daily subcutaneous elamipretide or placebo and did not meet either primary endpoint. The difference in six-minute walk distance was -3.2 metres (95% CI -18.7 to 12.3, p = 0.69) and the difference in total fatigue score was -0.07 (95% CI -0.10 to 0.26, p = 0.37). ^[20]
• Human studyA later post hoc analysis of that trial looked at genetic subgroups. Participants with defects in the genes that maintain mitochondrial DNA walked 25.2 metres further against 2.0 metres on placebo (p = 0.06), and within that group those with chronic progressive external ophthalmoplegia improved 37.3 metres against -8.0 metres (p = 0.0024). These are hypothesis-generating analyses done after the trial failed, and a follow-up Phase 3 trial was designed to test them. ^[21]
• Human studyIn Barth syndrome, an ultra-rare X-linked disorder, 10 patients entered the open-label extension of the TAZPOWER trial and 8 reached week 168. Six-minute walk distance improved significantly at every extension time point, cumulatively 96.1 metres by week 168 (p = 0.003), with fatigue scores below baseline throughout and left ventricular volumes trending better. Everyone knew they were receiving the drug and there was no concurrent placebo group. ^[22]
• FDA labelThe approval rests on a narrow reading of that programme. In the randomised, placebo-controlled crossover study of 12 Barth syndrome patients, elamipretide was not superior to placebo on either primary endpoint, and knee extensor muscle strength did not increase during the randomised phase; the strength gains appeared only in the uncontrolled extension, where median change from baseline was 34 newtons at week 12 and 63 newtons at week 168. FDA granted accelerated approval on that intermediate endpoint, with continued approval possibly contingent on a confirmatory trial. ^[16]

SS-31 side effects and risks

The FDA-reviewed safety record here comes from people with Barth syndrome or primary mitochondrial myopathy taking the approved product under supervision, not from the healthy adults who buy research-chemical vials labelled SS-31.

• FDA labelInjection-site reactions are the most common adverse reactions on the label. In the placebo-controlled crossover study, where all 12 patients had a period on drug and a period on placebo, injection site erythema occurred in all 12 on drug against 3 on placebo, pain in 9 against 5, induration and pruritus in 8 each against 2, and bruising and urticaria in 3 each against none on placebo. ^[16]
• FDA labelEosinophil counts rose frequently when dosing continued for 30 days or more, peaking around 90 days after the first exposure with a mean increase of roughly 0.5 to 0.6 x 10^3 per microlitre, and returning to baseline after 6 to 12 months of continued use or after stopping. The label records no symptoms or other laboratory changes tied to it. ^[16]
• FDA labelHypersensitivity reactions, including serious allergic reactions needing emergency treatment, have been reported. They have included rash, papular lesions, eczematous dermatitis and cough, and can begin anywhere from minutes to months after starting. The label says a serious reaction means stopping the drug permanently and treating with epinephrine, antihistamines and corticosteroids as needed; serious hypersensitivity to elamipretide or any excipient is a contraindication. ^[16]
• FDA labelThe approved product contains 20 mg of benzyl alcohol per millilitre as a preservative and is not approved for neonates. Benzyl-alcohol-containing drugs given intravenously to low-birth-weight and preterm newborns have caused serious, sometimes fatal, metabolic acidosis progressing to neurotoxicity and in some cases gasping syndrome, and the minimum amount at which this happens is not known. ^[16]
• Human studyIn the mitochondrial myopathy crossover trial, injection-site reactions were the most common adverse events with elamipretide, affecting 80% of participants, mostly mild, with no serious adverse events or deaths. The Phase 3 trial that followed reported adverse events that were mostly mild to moderate. ^[19][20]

Other things to know

• The largest and best-controlled trial, in primary mitochondrial myopathy, did not meet its primary endpoints on the six-minute walk test or fatigue score.
• The Barth syndrome approval is an accelerated approval resting on muscle strength, an intermediate endpoint, not yet on confirmed clinical benefit, and the long-term Barth data come from an open-label extension with no concurrent placebo group.
• Every trial is in a diagnosed condition, and the approval is for Barth syndrome alone. Healthy adults buying it for energy or longevity are the one group nobody has studied.

Reported side effects and what the studies measured: SS-31 side effects.

Where this vial size comes from

SS-31 is sold as a 50 mg vial by the page below, each checked on the date shown. I list them as evidence that this size exists, not as a recommendation to buy from them.

• Next Level PharmvendorLists it as: SS-31 size selector: 50mg option · checked 2026-09-28

The doses come from the sourced common protocol on the SS-31 dosing page, and every number on this page is arithmetic on those doses and this vial size.

Other SS-31 vial sizes

• 10 mg vial
• 30 mg vial
• 50 mg
• 280 mg vial

Questions

How much water do I add to a 50 mg SS-31 vial?

There is no single correct amount: water changes how many units a dose is, not how many doses the vial holds. With 1 mL the vial is 50 mg/mL and 40 mg is 80 units (0.8 mL) on a U-100 insulin syringe. The units table gives 1 mL.

How many doses are in a 50 mg SS-31 vial?

1 dose at 40 mg.

How long does a 50 mg SS-31 vial last?

At 40 mg a dose and once daily, about 0.1 weeks. How long a mixed vial keeps is a separate limit; see storage below.

How many 50 mg vials do I need for a 4-week run?

23 vials at 40 mg 7 times a week for 4 weeks.

What does 1 unit equal in a 50 mg SS-31 vial?

500 mcg with 1 mL of bacteriostatic water, on a U-100 syringe.