In the treatment of scabies infection in children up to 2 years of age, age-based ivermectin dosing yields high response rates and is well-tolerated, according to the open-label phase 2 ITCHY 2 study.
The age-based dosing strategy used in the study involved dividing a 3-mg ivermectin tablet—the only licensed formulation currently available. A quarter of a tablet (0.75 mg) was given to children aged 3–7 months, a half of a tablet (1.5 mg) to children aged 8–12 months, and a whole tablet (3 mg) to children aged 13–24 months. Treatment was administered on day 1, and a second dose was given on day 14 to complete treatment.
Drug exposure
The overall mean plasma ivermectin concentrations in children aged 3–24 months and weighing ≥2 kg who received oral ivermectin using aged-based dosing was comparable to that reported in children 5–11 years using the licensed 200-ug/kg dose (mean area under the curve [AUC0-∞], 835 vs 855 μg*h/L; p=0.65). [ESPID 2026, abstract OP-012 / #245]
“Children aged 3–7 and 13–24 months achieved comparable drug exposure from 0.75 and 3 mg ivermectin, respectively (mean AUC0-∞, 790 and 1,058 μg*h/L),” reported lead author Prof Amanda Gwee from the University of Melbourne, Parkville, Australia, during her presentation at the annual ESPID meeting.
Meanwhile, “children aged 8–12 months receiving 1.5-mg ivermectin achieved slightly lower drug exposure (mean AUC0-∞, 674 μg*h/L),” Gwee added.
Response rates
Improvements were observed in 96 percent of children overall, with complete resolution of scabies infection observed in 83 percent and partial resolution in 13 percent.
Among children 8–12 months who received 1.5-mg ivermectin, 90 percent showed clinical improvement, despite the slightly lower drug exposure.
“When we did further simulations, we found that we could actually give [8–12-month-old children] three quarters of a dose to achieve comparable exposure. This could be a dosing strategy that you take into the future,” Gwee said.
Safety profile
Treatment was well-tolerated, with only 6 percent of children experiencing adverse effects, she noted. “Importantly, there were no episodes of neurotoxicity.”
However, reinfection rate was high at 23 percent. Gwee attributed this to the unavailability of ivermectin and permethrin for the household members, “so, they were treated with topical zinc ointment.”
The ITCHY 2 study
Conducted across five health centres in Lao PDR, ITCHY 2 included 120 children (49 percent female) aged 3–24 months with a median weight of 7.9 kg. All children had typical scabies, mostly on the torso/buttocks (85 percent). None had comorbidities.
The age-based dosing strategy was based on population pharmacokinetic data from an earlier study demonstrating comparable drug exposure between children aged 5–15 years and weighing 5–15 kg who received the licensed 200-µg/kg ivermectin dose and children aged 2–4 years and weighing 10–14 kg who received the 3-mg ivermectin tablet (median area under the curve [AUC], 1,001 vs 976 µg/L.h, respectively). [PLoS Negl Trop Dis 2020;14:e0008886]
“The reason why we rounded the dose to milligrams rather than micrograms per kilos is because ivermectin is given as part of mass drug administration programs. It’s only available as a 3-mg tablet,” Gwee said. “We wanted to make it easy for administration.”
The author shared that she and her team are currently developing an ivermectin infant formula preparation to run in the next trial. “We have submitted ethics for our next phase 2 trial of ivermectin dosing in children under three months of age [ITCHY 3], and we have submitted a grant application to move into a phase 3/4 trial called ITCH FREE, comparing oral ivermectin with topical permethrin for scabies in young children.”