Ivermectin for Sarcoptes scabiei hyperinfestation

OBJECTIVES: Crusted (Norwegian) scabies is an unusual variant of scabies caused by hyperinfestation with Sarcoptes scabiei. It has high morbidity, and secondary bacterial skin sepsis may result in life-threatening bacteremia. An open label study of oral ivermectin was carried out in patients with crusted scabies refractory to topical therapy. METHODS: Patients with refractory crusted scabies were prescribed oral ivermectin, one to three doses of 200 mg/kg at 14-day intervals, combined with topical scabicide and keratolytic therapy. RESULTS: Of the 20 patients who received ivermectin, 8 had a complete initial clinical response, a partial response was achieved in 9, and minimal improvement occurred in 3. Three doses of ivermectin were curative for 8 of 10 cases, but recurrence of scabies from presumed reinfestation occurred in at least half of these. CONCLUSION: The authors conclude that ivermectin is effective for crusted scabies; however, multiple doses may be required to achieve a cure, and recurrence 6 or more weeks after completing treatment is common.