Background and aims Loberamisal is a small-molecule agent that inhibits the nNOS-postsynaptic density protein 95 coupling and enhances α2-containing γ-aminobutyric acid type A receptor, which has been shown effective in animal studies. This trial aimed to investigate its safety and therapeutic efficacy in patients with acute ischaemic stroke (AIS) within 48 hours of symptom onset. Methods Patients were randomly assigned in a 1:1:1:1 ratio to one of four groups: a low-dose loberamisal group (20 mg/dose), a medium-dose group (40 mg/dose), a high-dose group (60 mg/dose) or a placebo group. All patients received a continuous intravenous infusion treatment once a day for 10 days (60±10 min/dose). The primary efficacy outcome was the proportion of patients achieving an excellent functional outcome (a modified Rankin Scale score of 0–1 at 90 days). The primary safety outcome was the incidence of adverse events (AEs). Results A total of 240 patients were randomised, of whom 224 received study treatment from 4 June 2023 to 18 November 2023. The proportion of patients with excellent functional outcome was highest in the medium-dose group (76.7%, 46/60), followed by the high-dose group (70.0%, 42/60), the low-dose group (67.8%, 40/59) and the placebo group (60.7%, 37/61) (p=0.164). Regarding safety, 210 patients experienced at least one AE, with incidences of 80.0% (48/60), 88.3% (53/60) and 91.5% (54/59) in the high, medium and low-dose loberamisal groups, respectively, and 90.2% (55/61) in the placebo group (p=0.260). Conclusions Loberamisal injection was well tolerated in patients with AIS within 48 hours of symptom onset in China. The efficacy and optimal dosage of loberamisal for AIS need prospective validation. Trial registration number ChiCTR2400081662, NCT06429384 .