This is an open label prospective pharmacokinetic single arm study in Laos PDR. This study will be embedded within a cluster-randomized controlled trial of interventions to address childhood undernutrition (SUANHOAM Trial, ACTRN12620000520932) and involves a collaboration with the Murdoch Children's Research Institute, Burnet institute and Lao Tropical and Public Health Institute.

ITCHY Study:

The primary objective is to determine in young children aged 2 to <5 years and weighing 10 to <15 kg if an ivermectin dose of 3 mg achieves comparable drug exposures to the recommended dose in older children. It aims to provide reliable evidence for a safe and effective dose of ivermectin in young children who are especially vulnerable to scabies infections and the associated secondary complications.

ITCHY2 Study:

An embedded phase 2 multicentre, open label prospective pharmacokinetic study in Laos PDR of ITCHY Study. The primary objective is to determine the plasma ivermectin drug exposure in children aged 3 months to 2 years and weighing ≥2 kg receiving an age specific ivermectin dose.

ITCHY study:

100 children aged 2 to <5years and weighing 10 to <15 kg with clinically diagnosed scabies infection in the participating sites in Laos PDR will be approached for recruitment into the study if eligible (see eligibility criteria) and allocated into one of four blood sampling groups with 25 participants in each group. The 3mg dose of ivermectin will be administered orally and blood samples will be collected at two different time points accordingly to blood sampling groups allocation after the first 3mg dose of ivermectin. Clinical responses will be assessed on day 14. A second dose of ivermectin to complete the treatment will only be administered if the first dose has been tolerated by the participants. The 3mg ivermectin drug exposure, safety and effectiveness will be measured.

ITCHY2 Study:

120 children aged 3 months to 2 years and weighing ≥2 kg with clinically diagnosed scabies infection in the participating sites in Laos PDR will be approached for recruitment into the study if eligible (see eligibility criteria) and allocated into one of four blood sampling groups with 30 participants in each group. An age specific dose of ivermectin will be administered orally and blood samples will be collected at two different time points accordingly to blood sampling groups allocation after the first dose of ivermectin.

Age specific ivermectin dose:

• 0.75mg of ivermectin will be given to participants aged 3 to 7 months
• 1.5mg of ivermectin will be given to participants aged 8 to 12 months
• 3mg of ivermectin will be given to participants aged 13 to 24 months

Clinical responses of the participants will be assessed on day 14. A second age specific dose of ivermectin to complete the treatment will only be administered if the first dose has been tolerated by the participants. The ivermectin plasma drug exposure, safety and effectiveness will be measured.

Inclusion Criteria

ITCHY study:

Children aged 2 to <5 years and weighing 10 to <15 kg with scabies infection as clinically diagnosed by the treating clinician.

ITCHY2 study:

Children aged 3 months to 2 years and weighing ≥2 kg with scabies infection as clinically diagnosed by the treating clinician.

Exclusion Criteria:

ITCHY and ITCHY2 study:

• Children with known liver disease
• Children with known allergy to ivermectin
• Children with concomitant warfarin use
• Children with known neurological disease
• Children already receiving topical treatment for scabies

The de-identified data set collected for the analysis of the ITCHY trial will be available six months after publication of the primary outcome.

6 months after publication of primary outcome

Prior to releasing any data the following are required: a data access agreement must be signed between relevant parties, the ITCHY Trial Principle and Associate Investigators must see and approve the analysis plan describing how the data will be analysed, there must be an agreement around appropriate acknowledgement and any additional costs involved must be covered. Data will only be shared with a recognised research institution which has approved the proposed analysis plan.