Trying to Keep Ahead of Lice: A Therapeutic Challenge

C. E. Malcolm, MD, CCFP; J. N. Bergman MD, FRCPC


Skin Therapy Letter. 2006;11(10):1-6. 

In This Article

Oral Agents


Ivermectin, an antihelminthic drug, has been suggested for off-label use in the treatment of head lice at a dosage of 200ìg/kg, repeated in 7-10 days to kill newly hatched nymphs.11 It is an effective pediculicide and the mechanism of action is thought to be on the symbiotic gram-negative bacteria that are required to digest blood. With the concern of possible neurotoxicity, the safety and efficacy of this agent for head lice remains to be established.[3] No resistance has been reported to date and it may be used after failure with topical pediculicides. Treatment with this agent may benefit patients with extensive infestations or infestations with multiple types of ectoparasites.[3] Oral ivermectin should not be used in children weighing less than 15kg.[4] Topical ivermectin holds some promise but warrants further study.[3]


Oral TMP/SMX has been shown to be effective in small studies of off-label use.5 It presumably works by destroying the gut flora of the louse, thereby interfering with its ability to synthesize vitamin B and ultimately causing death.[5] Combination therapy with topical agents may improve it's efficacy.


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