Ivermectin dosing for children under 2 years.

Objectives: Ivermectin is effective against scabies but not licensed for children weighing <15 kg. We aimed to identify an ivermectin dosing strategy for children aged <2 years.

Methods: Doses for three age subgroups under 2 years were simulated by incorporating a maturation function for metabolizing enzymes into a population pharmacokinetic (PopPK) model to achieve median plasma AUC0-∞ between 80% and 125% of that observed in children aged 5-15 years receiving the standard 200 μg/kg dose (AUC0-∞ 976 μg/L h). Patient covariates were sampled from the National Health and Nutrition Examination Survey dataset. Final doses were rounded to feasible fractions of a 3 mg tablet.

Results: For infants aged 3-7 months, a 0.75 mg dose (one-fourth tablet) resulted in a median AUC0-∞ of 835 μg/L h [IQR: 632-1017]; for 8-12 months, a 1.5 mg dose (one-half tablet) yielded 848 μg/L h [IQR: 774-934]; and for 13-24 months, a 3 mg dose (one tablet) resulted in 1033 μg/L h [IQR: 943-1173]. All doses achieved median exposures within 80%-125% of the reference AUC in older children.

Conclusions: A dosing strategy for ivermectin in children aged 3 months-2 years was developed using a CYP3A4 maturation-based PopPK model. This regimen will be evaluated in an upcoming clinical trial to inform safe and effective scabies treatment in young children.