SS-31 Side Effects: What Studies and Users Report
What FDA labels and clinical studies report for SS-31, how strong that evidence is, and what is still unknown.
Side effects reported in studies
Adverse reactions from the FDA label come first, then side effects reported in individual studies. Frequencies are quoted as the source gives them; animal results are labelled.
| Side effect | How common | Study type | Source |
|---|---|---|---|
| Any local administration reaction | 12 of 12 (100%) on elamipretide vs 8 of 12 (67%) on placebo | FDA label | FDA label (Forzinity) |
| Injection site erythema | 12 of 12 (100%) vs 3 of 12 (25%) on placebo | FDA label | FDA label (Forzinity) |
| Injection site pain | 9 of 12 (75%) vs 5 of 12 (42%) on placebo | FDA label | FDA label (Forzinity) |
| Injection site induration | 8 of 12 (67%) vs 2 of 12 (17%) on placebo | FDA label | FDA label (Forzinity) |
| Eosinophilia“Increases in absolute eosinophil counts were noted frequently in studies where duration of administration of FORZINITY was 30 days or greater.” | Frequency not stated | FDA label | FDA label (Forzinity) |
| Hypersensitivity reactions“Hypersensitivity reactions, including serious allergic reactions requiring emergency medical intervention, have been reported in patients receiving FORZINITY.” | Frequency not stated | FDA label | FDA label (Forzinity) |
| Injection site reactions | 86% vs 71% placebo | Human RCTn = 176 | Ophthalmology science 2025, PMID 39605874 |
| Most adverse events mild to moderate | most | Human RCTn = 218 | Neurology 2023, PMID 37268435 |
| Injection site reactions | 80% | Human RCTn = 30 | Journal of cachexia, sarcopenia and muscle 2020, PMID 32096613 |
| No serious adverse events | none | Human RCTn = 36 | Circulation. Heart failure 2017, PMID 29217757 |
| Injection-site reactions | most common | Human uncontrolled trialn = 10 | Genetics in medicine 2024, PMID 38602181 |
What is not known
- How common each effect is at the doses people use outside of studies.
- Effects that take longer to appear than the length of the published studies.
- How SS-31 interacts with other medicines and supplements.
- Whether research-grade products, which are not checked by the FDA, behave like the material used in studies.
When to get medical help
Get urgent care for: trouble breathing, swelling of the face or throat, a widespread rash, severe or lasting stomach pain, fainting, or an injection site that becomes hot, red and spreading.
This is not a complete list. A doctor or pharmacist can help you judge whether a symptom is related.
Common questions
What are the side effects of SS-31?
The FDA label lists any local administration reaction, injection site erythema, injection site pain among others. The table on this page gives how often each happened and links each source.
Is SS-31 safe?
SS-31 has an FDA-approved label that lists its known risks. That label covers the approved product used as prescribed, not compounded or research-chemical versions.
More on SS-31
DosageDoses used in published studies, with the source for each.CalculatorVial, water and dose to syringe units.ResultsStudy outcomes and when they were measured.PricePrice per mg and per week from dated listings. No vendor links.Legal statusFDA, compounding and WADA status with dates.50 mg vialConcentration and unit tables for the 50 mg size.
Sources
- 1FORZINITY (ELAMIPRETIDE HYDROCHLORIDE) INJECTION [STEALTH BIOTHERAPEUTICS INC.]FDA label (Forzinity), DailyMed · current labeldailymed.nlm.nih.govAccessed 2 Oct 2026
- 2ReCLAIM-2: A Randomized Phase II Clinical Trial Evaluating Elamipretide in Age-related Macular Degeneration, Geographic Atrophy Growth, Visual Function, and Ellipsoid Zone Preservation.Ophthalmology science · 2025PMID 39605874Accessed 2 Oct 2026
- 3Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial.Neurology · 2023PMID 37268435Accessed 2 Oct 2026
- 4A randomized crossover trial of elamipretide in adults with primary mitochondrial myopathy.Journal of cachexia, sarcopenia and muscle · 2020PMID 32096613Accessed 2 Oct 2026
- 5Novel Mitochondria-Targeting Peptide in Heart Failure Treatment: A Randomized, Placebo-Controlled Trial of Elamipretide.Circulation. Heart failure · 2017PMID 29217757Accessed 2 Oct 2026
- 6Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER.Genetics in medicine : official journal of the American College of Medical Genetics · 2024PMID 38602181Accessed 2 Oct 2026
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