Is a single oral dose of ivermectin sufficient in crusted scabies?

Controlling scabies in institutional settings: a review of medications, treatment models, and implementation

Scabies is a global problem and a significant source of morbidity in nursing home residents and workers because of its highly contagious nature. It is also a problem in hospitals that care for the elderly, the debilitated, and the immunocompromised. New outbreaks continue to occur, despite controlling the recurrent epidemics. Scabies manifests as papules, pustules, burrows, nodules, and occasionally urticarial papules and plaques. Most of the patients with scabies experience severe pruritus. A subset of patients have crusted or Norwegian scabies. These patients, who are usually debilitated or immunocompromised, do not experience the urge to scratch, and therefore do not scratch their own skin. Diagnosis of scabies is based on patient history, physical examination, and demonstration of mites, eggs, or scybala (black or brown football-shaped masses of feces of scabies) on microscopic examination. Scabies can be treated with topical or oral therapies. Topical treatments include 5% permethrin cream, 1% lindane (gamma benzene hexachloride) lotion, 6% precipitated sulfur in petrolatum, crotamiton, malathion, allethrin spray, and benzyl benzoate. Ivermectin, the only oral treatment, is not approved for scabies in the US. Most authorities advocate using a scabicide several times, specifically once a week over a period of 2-3 weeks. In an outbreak of scabies in a nursing home, residents, staff, and frequent visitors should all be treated even if they are not symptomatic. Ivermectin is useful in treating patients with Norwegian or crusted scabies, or who are debilitated. Ivermectin has no serious reported adverse effects. Model treatment plans to stop scabies epidemics have been developed. These plans coordinate treatment of all persons exposed (including ivermectin for debilitated patients), isolation of infected patients, disinfection of objects that patients have come into contact with, and education and reassurance of the medical staff. Failure to coordinate notification, education, treatment, and disinfection leads to failure to control scabies epidemics. Control of epidemics of institutional scabies requires attention to treatment effects and logistics. Treatment is low risk, but cumbersome because many individuals need be treated. It is advisable to restrict, where possible, the number of staff members that deal with scabies patients to limit the spread of the scabies. Prolonged surveillance is required for the eradication of institutional scabies. While the foregoing plans require coordination of all involved personnel and sustained efforts, they are necessary to halt the spread of scabies to patients and staff, to enhance their morale, and to prevent deterioration of labor and public relations.

Ivermectin

Ivermectin is a potent antiparasitic drug and the first commercially available member of a new class of drugs (macrocyclic lactones) that has been approved for human use. Ivermectin has already proven to be highly effective in the elimination of river blindness as a public health burden. Side effects have been minor, and patient acceptance is good. Promising results in off-label applications for ectoparasitic infestations are increasingly important as resistance to topical therapy becomes more prevalent Ivermectin represents an advance in the therapeutic armamentarium and should be considered in appropriate cases.