Background: Ivermectin is effective for treating scabies but is unlicensed for children <15 kg. Our previous trial in children aged 2-4 years showed ivermectin was safe and effective, with a 3 mg dose achieving drug exposures comparable to the licensed dose in children weighing ≥15 kg. Using population pharmacokinetic modelling, an age-based dosing strategy for children aged 3-24 months was derived to achieve comparable drug exposures.
Methods: Multicentre, phase 2 trial across four health centres in Lao PDR (Clinicaltrials.gov NCT05500326). Children aged 3–24 months weighing ≥2 kg with scabies received age-based ivermectin doses: 0·75 mg (3–7 months), 1·5 mg (8–12 months), and 3 mg (13–24 months). Baseline haemoglobin and two dried blood spot ivermectin concentrations were measured. Clinical outcomes and adverse effects were assessed on day 14, when a second dose was administered. The primary outcome was the geometric mean plasma ivermectin exposure (AUC0–∞) after the first dose, compared with a historical cohort of children aged 5–11 years receiving 200 μg/kg (target range 80–125%), clinical improvement and adverse effects were also assessed.
Findings: Overall, 120 children with a median age of 0·75 years (IQR 0·5–1·25) were enrolled. The geometric mean ivermectin AUC0–∞ was comparable to the historical cohort (835 vs 885 μg·h/L; p=0·65). Children aged 3–7 months and 13–24 months had exposures within the target range (89% and 120%), while those aged 8–12 months had slightly lower exposure (674 μg·h/L; 76%). Clinical improvement occurred in 115/120 (96%) children with mild adverse effects in 7/120 (6%).
Interpretation: Age-based ivermectin dosing in children 3–24 months weighing ≥2 kg achieved comparable plasma exposures to licensed dosing in older children and was safe and highly effective for scabies.