OTCs Today
Daniel L. Krinsky, RPh, MS
Head lice are the most common cause of lice infestation. Outbreaks of lice infestation are routinely found in places such as schools and daycare centers, and all socioeconomic groups are affected. Outbreaks usually peak after the opening of schools each year, between August and November. Infestations are most commonly spread through direct head-to-head contact with an infected person. Sharing personal items such as caps, hairbrushes, and combs is unlikely to cause spreading. Objectives for self-treatment are
to rid the body of lice and to implement measures to prevent future infestations.
Control of pediculosis requires both pharmacologic and nonpharmacologic intervention. Because none of the pediculicides kill 100% of lice eggs, the National Pediculosis Association recommends visually inspecting the hair carefully for nits and combing with an FDA-approved nit comb. Removing nits is helpful in treating and controlling head lice. Avoid direct physical contact with an infested individual, and do not share articles such as combs, brushes, towels, caps, and hats. Wash clothing and bedding in hot water, and dry in a clothes dryer to kill lice and their nits. An alternative to washing is to seal contaminated items in a plastic bag for 2 weeks. Wash hairbrushes and combs in very hot water, and vacuum carpets, rugs, and furniture regularly and thoroughly.
What treatments are available?
Three nonprescription pediculicide agents are available for treating pediculosis: synergized pyrethrins, permethrins, and most recently, ivermectin.
Health care providers should be concerned about significant resistance to synergized pyrethrins and permethrins, which has continued to increase over the last several years. Synergized pyrethrins block nerve impulse transmission, causing the insect’s paralysis and death. Addition of piperonyl butoxide to pyrethrins synergizes their insecticidal effect through inhibition of pyrethrin breakdown. The treatment is repeated in 7 to 10 days to kill any remaining nits that have since hatched. These preparations may be used on children ages 2 years and older, but they should only be used in pregnancy and lactation if prescribed by a health care provider. Most adverse reactions are cutaneous and include irritation, erythema, itching, and swelling.
Permethrin, a synthetic pyrethroid, acts on the nerve cell membrane of lice, disrupting the sodium channel, delaying repolarization, and causing paralysis and death of the parasite. It is applied in sufficient quantities to cover or saturate washed hair and scalp. The rinse has residual effects for up to 10 days; therefore, retreatment in 7 to 10 days is not required unless active lice are detected.
Primary adverse effects, which can occur in up to 10% of the patient population, include transient pruritus, burning, stinging, and irritation of the scalp. Permethrin should not be used on infants younger than 2 months. No significant difference exists in effectiveness of permethrin versus pyrethrin and piperonyl butoxide combination when treatment consists of two applications. Each product is contraindicated in patients who are sensitive to the active ingredients or to chrysanthemums. Combing with a lice comb is recommended following treatment.
FDA recently approved 0.5% ivermectin lotion as a one-time treatment of head lice infestation in individuals ages 6 months and older (see New & Approved in this issue, page 10). Ivermectin binds to chloride ion channels, leading to enhanced permeability of cell membranes and hyperpolarization of nerve cells, causing the insect’s paralysis and death.
A variety of alternative therapies have been used to eliminate lice infestations; however, none are FDA approved, and there is very limited evidence, if any, of effectiveness.
Patient counseling
Counsel patients with confirmed head lice infestations on which product is best for their situation and how to use it properly, and discuss preventive measures. For all three treatments, counsel patients to apply the medication to the affected area for 10 minutes, then rinse or shampoo the treated area as recommended. Advise patients to avoid contact with eyes and mucous membranes.