What is the diagnosis and treatment for scabies (sarcoptic mange)?

From the Guidelines

Scabies treatment should prioritize a combination of topical and oral medications for crusted scabies, with permethrin 5% cream and oral ivermectin 200 ug/kg on days 1,2,8,9, and 15 being the recommended treatment approach. This is based on the guidelines from the MMWR Recommendations and Reports 1. The treatment of scabies involves several key considerations, including:

• The use of permethrin 5% cream as a first-line topical treatment, applied from neck to toes and left on for 8-14 hours before washing off, with a repeat application after 7 days to kill newly hatched mites.
• Alternative treatments such as ivermectin (oral medication, 200 mcg/kg, repeated after 1-2 weeks), benzyl benzoate 25% lotion, or crotamiton 10% cream.
• The importance of treating all household members and close contacts simultaneously, even if asymptomatic, to prevent reinfestation.
• Environmental decontamination, such as washing bedding, clothing, and towels used within 3 days before treatment in hot water and drying on high heat, is also crucial 1.
• Itching may persist for 2-4 weeks after successful treatment due to the body's allergic response to the dead mites.
• Crusted (Norwegian) scabies, a severe form seen in immunocompromised individuals, requires more aggressive treatment, often combining topical and oral medications, as outlined in the guidelines 1.

From the FDA Drug Label

Permethrin Cream, 5% is indicated for the treatment of infestation with Sarcoptes scabiei (scabies). Thoroughly massage Permethrin Cream, 5% into the skin from the head to the soles of the feet. For eradication of scabies ( Sarcoptes scabiei) and for symptomatic treatment of pruritic skin.

• Permethrin (TOP) and crotamiton (TOP) are indicated for the treatment of scabies.
• The treatment of scabies with permethrin (TOP) involves applying the cream from the head to the soles of the feet and washing it off after 8 to 14 hours 2, 2.
• Crotamiton (TOP) is also used for the eradication of scabies and symptomatic treatment of pruritic skin 3.
• ONE APPLICATION OF PERMETHRIN is generally curative, but patients may experience persistent pruritus after treatment, which is rarely a sign of treatment failure 2.

From the Research

Treatment Options for Scabies

• Topical permethrin is considered the most effective treatment for scabies, with a cure rate of 61.8% to 87.2% in adult immunocompetent patients 4.
• The application of 5% permethrin cream, once daily for two consecutive days, is more effective than a single application 4.
• Topical ivermectin is also an effective treatment, with a cure rate of 63.1% to 84.2% at the 2-week and 4-week follow-up, respectively 5.
• Permethrin 2.5% cream is effective in 65.8% to 89.5% of patients at the 2-week and 4-week follow-up, respectively 5.

Application and Administration

• Topical permethrin 5% cream should be applied from the scalp to the toes, including all external surfaces of the body, especially in cases where the scalp is involved 6.
• The cream should be stored in the refrigerator and applied cold to the entire skin surface, left on for 24 hours 4.

Diagnosis and Epidemiology

• Scabies is a skin infestation caused by the human itch mite (Sarcoptes scabiei va. hominis), characterized by thread-like papules, intense pruritus, and dermatitis 7.
• The incidence of scabies is apparently rising, and the diagnosis is confirmed by microscopic or dermatoscopic demonstration of scabies mites 7.

Treatment Failure and Resistance

• Known causes of treatment failure include improper application of external agents, failure of repeated treatment with ivermectin, and incomplete decontamination of furnishings and clothes 7.
• There is a rising number of well-documented cases of poor response to permethrin, although there is no direct proof of resistance of scabies mites to permethrin 7.