Design: Phase 3, randomised, double-blind, placebo-controlled; stopped for futility
Population: 271 patients aged 3-21 with sickle cell pain crises, 10 US children's hospitals
Primary outcome: Time to crisis resolution (last IV opioid dose)
Effect: Median 60.8 vs 65.8 hours; difference 7.2 h (95% CI -21.6 to 35.9)

STArT, a phase 3 double-blind trial in 10 US children's hospitals, randomised 271 patients aged 3 to 21 presenting to the emergency department with sickle cell pain needing parenteral opioids. They received intravenous arginine (200 mg/kg, then 100 mg/kg every 8 hours) or saline. Published in JAMA on 13 October 2026.

The trial was stopped early for futility. Time to crisis resolution was a median of 60.8 hours with arginine and 65.8 hours with placebo, a difference that was not significant (95% CI -21.6 to 35.9 hours). Opioid use, pain scores, patient-reported outcomes and safety did not differ.

Smaller single-centre trials had suggested arginine was opioid-sparing. This larger trial did not confirm it, a familiar pattern when promising phase 2 results meet a rigorous test.

Standard care stands: rapid analgesia, hydration, and attention to acute chest syndrome.

Do not use intravenous arginine for sickle cell pain crises outside trials
Give the first dose of analgesia promptly, ideally within an hour of arrival
Reassess pain and sedation frequently during opioid treatment
Watch for acute chest syndrome: new chest pain, fever, hypoxia or infiltrate
Use incentive spirometry in admitted patients

Why it matters

A treatment that looked promising in small trials did not hold up in a larger one.

The statistics, in plain English

The confidence interval for the difference in time to resolution is very wide, from about 22 hours worse to 36 hours better, so the trial was stopped when it became clear a clinically useful benefit was unlikely.