Treatment of scabies
Perhaps the most difficult job in treatment of scabies is treating asymptomatic contacts. Physicians may be reluctant to prescribe, and contacts themselves may be reluctant to take, appropriate treatment. These individuals often spread the infection for 4 to 6 weeks before they develop sensitization and clinical symptoms. Thus, it is essential that these asymptomatic contacts be treated or a cycle of reinfestation will be created.3 All sexual contacts, close personal contacts, and household contacts from within the preceding month should be examined and treated.8
Permethrin cream. The recommended treatment by the Centers for Disease Control and Prevention (CDC) is permethrin cream (5%) applied to all areas of the body from the neck down and thoroughly washed off after 8 to 14 hours. This recommendation includes careful application under fingernails, between toes, and on palms and soles. Infants may need the face and scalp treated in addition. Treatment of the face beyond infancy frequently results in a contact irritant dermatitis. Permethrin is effective and safe but costs more than lindane.8
Lindane. The CDC guidelines offer 2 alternatives to permethrin. One alternative, lindane 1% cream or lotion, can be applied in a thin layer to all areas of the body from the neck down and thoroughly washed off after 8 hours.
Lindane should not be used immediately after a bath or shower, and should not be used by persons who have extensive dermatitis, pregnant or lactating women, or children aged less than 2 years. Lindane resistance has been reported, including in the United States. Seizures have occurred when lindane was applied after a bath or used by patients who had extensive dermatitis. Aplastic anemia following lindane use also has been reported. Infants, young children, and pregnant or lactating women should not be treated with lindane; they can be treated with permethrin.8
Applying topical treatments. Topical scabicides should be applied to all skin from neck down, including intertriginous areas and the gluteal fold. The medication needs to be reapplied to hands if the hands are washed after application. It is advisable to cut fingernails short before applying scabicides and to ensure that scabicide is applied under fingernails. A toothpick can be used if necessary to assist in application under nails. In infants and small children, medication should be applied to face and scalp, avoiding the periorbital area.6
Other treatments. Ivermectin, the third treatment recommended by the CDC, can be administered as a single dose of 200 mcg/kg orally, and repeated in 2 weeks. Ivermectin is not recommended for pregnant or lactating patients. The safety of ivermectin in children who weigh less than 15 kg has not been determined.8
Some specialists recommend retreatment after 1 to 2 weeks for patients who are still symptomatic. Patients who do not respond to the recommended treatment should be retreated with an alternative regimen.8
Patients who have uncomplicated scabies and also are infected with HIV should receive the same treatment regimens as those who are HIV-negative.8 For patients with crusted scabies, the optimal regimen is unknown because no controlled therapeutic trials have been conducted. Expert opinion suggests augmented and combined regimens should be used for this aggressive infestation. Lindane should be avoided because of risks of neurotoxicity with heavy applications.8 Control of scabies epidemics (eg, in nursing homes, hospitals, residential facilities) require treatment of the entire population at risk.