SS-31 (Elamipretide) common uses, half-life, side effects and more

SS-31 is elamipretide. It is a synthetic peptide that collects inside mitochondria and is meant to protect how cells produce energy. The FDA approved an injectable form in 2025 to improve muscle strength in adults and children who have Barth syndrome and weigh at least 30 kg. Barth syndrome is a rare inherited disorder of the mitochondria. That approval is narrow and prescription only. It does not establish the drug for any other use. Biohackers, longevity enthusiasts, and some athletes inject gray-market SS-31 off label for mitochondrial support, fatigue, and exercise recovery. Powder sold online as a research chemical comes from a different supply chain than the approved medicine and is not held to the same quality standards.

• Approved treatment to improve muscle strength in Barth syndrome at 30 kg or more
• Off-label mitochondrial support for fatigue and low energy
• Longevity and anti-aging self-experimentation
• Exercise recovery and endurance support in athletes

Once daily

The approved dose is 40 mg injected under the skin once daily for patients weighing at least 30 kg. Severe kidney impairment halves that to 20 mg once daily. Gray-market users inject far less than this and dose once daily rather than a few times a week. First-hand reports scatter from about 1 mg to 16 mg once daily. Many start low and work up toward about 10 mg. The tidy 2 to 5, 5 to 10, and 10 to 20 mg ladders sold as protocols are marketing rather than tested doses.

• People often run an SS-31 block for several weeks and then a MOTS-c block instead of injecting both at once

The terminal plasma half-life is about 3 to 4 hours in humans. Daily dosing produces no meaningful buildup in the blood. Longer durations sometimes cited reflect retention inside mitochondria rather than the plasma half-life.

The approved solution is refrigerated at 2 to 8 degrees Celsius and never frozen. An opened vial may stay refrigerated or sit at room temperature up to 25 degrees Celsius and is discarded 8 days after the first use.

• Injection-site redness, itching, pain, swelling, bruising, or hives are very common with daily dosing
• Firm lumps or nodules can build up at injection sites over time
• A rise in eosinophil white blood cells can appear after about a month of daily use and settles after stopping
• Rash, small raised skin bumps, or eczema-like dermatitis can signal a hypersensitivity reaction
• Serious allergic reactions including anaphylaxis have occurred and need emergency care

Elamipretide is an aromatic cationic tetrapeptide. It crosses cell membranes without a receptor and concentrates on the inner mitochondrial membrane. There it binds a lipid called cardiolipin. Cardiolipin organizes the proteins of the electron transport chain and shapes the folds where cells make energy. Binding it helps elamipretide protect the cytochrome c complex and keep electron transport efficient. This lowers wasteful electron leak and preserves ATP production in cell and animal studies. Early work described the peptide as a free-radical scavenger. The current account centers on cardiolipin binding instead. The exact molecular step is still debated. Some evidence points to cardiolipin-protein interfaces rather than free cardiolipin.

Human evidence is strongest for the approved Barth syndrome use. Even there it is thin. Approval rested on a small rare-disease program and a muscle-strength measure that still needs a confirmatory trial. The one randomized placebo-controlled Barth study missed its main endpoints of walking distance and fatigue. The FDA first rejected the drug in May 2025 before approving it four months later. Trials outside Barth syndrome have mostly failed. A phase 3 mitochondrial myopathy study and the macular degeneration and heart failure programs all missed their endpoints. The core mechanism work traces heavily to the inventor's own lab and has limited independent replication. Community longevity use is self-reported, rests mainly on one forum, and is not an independent evidence base.

• Approval covers only muscle strength in Barth syndrome and does not establish benefit for longevity, fatigue, or athletic recovery
• Research-chemical SS-31 can vary in identity, salt form, potency, sterility, and endotoxin content
• A serious hypersensitivity reaction to SS-31 or an excipient is a reason to stop and not restart it
• The approved solution contains benzyl alcohol and is not for use in newborns
• Severe kidney impairment requires halving the subcutaneous dose to 20 mg once daily
• Human safety in pregnancy and breastfeeding is unknown