Supplement analysis backed by scientific evidence · PT

← All supplements
Limited evidencePhysical performance

Inosine

Inosine was a 1980s-90s sports supplement that failed every controlled performance test, then had a second life as a urate-raising neuroprotectant for Parkinson's disease — until a phase 3 trial was stopped for futility. There is no good reason to take it, and a concrete reason not to.

What the science says

  • Does not improve exercise performance — repeatedly Limited evidence

    Ten competitive male cyclists took 5,000 mg/day for 5 days in a placebo-controlled study: no differences in Wingate peak power, end power, fatigue index, total work or post-test lactate, and no difference in work completed during a 30-minute self-paced ride. Time to fatigue in a supramaximal sprint was actually shorter on inosine (99.7 s) than placebo (109.7 s, p < 0.05). Earlier work on 3-mile treadmill run performance and VO2 peak, and a later cycling trial, reported the same absence of benefit. Serum uric acid rose, confirming subjects absorbed the dose — it simply did nothing useful.

  • Failed a phase 3 Parkinson's disease trial Strong evidence

    SURE-PD3 randomized 298 people with early Parkinson's disease and low baseline urate to inosine or placebo for up to 2 years. Inosine raised serum urate by 2.03 mg/dL from a 4.6 mg/dL baseline — a 44% increase, so the target was engaged — yet MDS-UPDRS progression was 11.1 points/year on inosine versus 9.9 on placebo (difference 1.26, 95% CI -0.59 to 3.11, p = 0.18). The study closed early on a prespecified futility analysis. This is a well-powered negative result and it settles the question.

  • Raising uric acid is the side effect, not the benefit Moderate evidence

    Inosine is a purine nucleoside that metabolizes to uric acid — that is its entire pharmacology. In SURE-PD3, the inosine arm had a markedly higher rate of kidney stones, the predictable consequence of sustained hyperuricemia. Any supplement whose measurable effect on your body is raising urate should be judged against the well-established harms of high urate: gout and urolithiasis.

Dosage & safety

Studied dosePerformance studies used 5,000-6,000 mg/day for 2-5 days. SURE-PD3 titrated 500-3,000 mg/day (up to 2 g three times daily) to a serum urate target of 7.1-8.0 mg/dL, under medical supervision with urate monitoring and stone surveillance. Neither regimen is appropriate for self-directed use — the first because it does not work, the second because it requires monitoring and still did not work.
SafetyThe principal hazard is uric acid elevation: kidney stones (significantly increased in the phase 3 trial) and precipitation of gout flares. Contraindicated in anyone with gout, existing hyperuricemia, a history of urate kidney stones, or renal impairment. GI upset is common. It directly opposes urate-lowering therapy such as allopurinol or febuxostat. Anyone with a condition predisposing to high purine turnover should avoid it. Sold as a dietary supplement in the US and used medically only within trials. Not on the WADA prohibited list — a distinction of no practical value for a supplement with a consistent record of not enhancing performance.

Scientific references

Where to buy

Swanson Vitamins, Inosine, 60 Veggie Caps (500 mg Per cap)

View on iHerb

Referral link — this site may earn a commission on purchases.

Related in Physical performance