18 April 2010

IVERMECTIN: A New Treatment Option for Resistant Scabies and Head Lice

Two of the most common infestations confronting the health care volunteer working in developing countries are scabies and head lice. Although neither is life threatening, both can cause significant discomfort and at times interfere seriously with quality of life.
Scabies is caused by the invasion of an almost microscopic mite into the skin, where it completes its life cycle. The most common sites are usually on the hands and arms, but can involve the entire body in small children and debilitated or aged adults. After some time the host develops an allergic very itchy rash, which more quickly recurs with re-infection. A number of treatments have been used. Lindane lotion is effective, but has fallen into disuse because of concerns about neurotoxicity. Permethrin cream is currently the most widely prescribed, but treatment failures and recurrences are common. Oral Ivermectin, widely used as a vermifuge, has been successfully used in a number of trials as a single dose of 200-400 micrograms/kg, repeated after one week. Success rates of 95% have been reported, even in cases of treatment failure with other approaches or difficult to treat cases of extensive generalized scabies.

Head lice have posed somewhat similar treatment difficulties. Lindane shampoo is no longer recommended. Permethrin 1% cream has been effective in the past, but is showing increased resistance. A recent study showed that ivermectin at a dose of 400 micrograms/kg repeated after one week in combination with nit combing resulted in a 97% clearance rate at 15 days, far superior to any other treatment regimen.

Ivermectin is currently available as 3 and 6 mg tablets. Only the brand name Stromectol is currently available for purchase in the US and is prohibitively expensive at around $6 per 3mg tablet. However, mission supply houses such as Blessings International have generic ivermectin available to health care volunteers for overseas use only, at about 20 cents per 6 mg tablet. Although ivermectin is not currently FDA approved for the treatment of either scabies or head lice, it is becoming more widely used throughout the world for this purpose. The side effect profile is low. It seems prudent for us to continue to use permethrin for the routine treatment of uncomplicated infestations with scabies and head lice, particularly in small children and women who are pregnant or breast feeding. Ivermective can be considered as a viable, safe alternative in cases of treatment failure, for institutional epidemics where mass local treatment is impractical, or for massive infection in immuno-compromised patients.

Submitted by Roger Boe, M. D.

References

1. Currie, B.J. et. Al. Permethrin and Ivermectin for Scabies. N. Engl. J Med 2010; 362: 717-725.

2. Chosidow, O. et. Al. Oral Ivermectin versus Malathion Lotion for Difficult-to Treat Head Lice. N. Engl. J Med 2010; 362: 896-905.

3. Boe, R. W. Scabies: An Update on Treatment; www.umvim4health blogspot.com 2009.

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