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Lice: Treatment & Medication
Updated: May 5, 2009
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- Differential Diagnoses & Workup
- Treatment & Medication
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Treatment
Emergency Department Care
- Patient therapy consists of 2 parts: medications and environmental control measures (see Further Outpatient Care).
- Consider providing medical treatment to all persons who have contact with patients who are infested, especially sexual partners.
- In the treatment of body lice, medications are less essential than environmental measures.
- Many infectious disease authorities recommend only environmental measures to treat body lice.
- Patients with body lice should have infested clothing removed and destroyed.
- If medical therapy is prescribed as an adjunct to environmental measures, one of the therapies listed in Medication may be selected.
Medication
The goal of medication is to eliminate the mite. Family members and sexual partners should be treated. Re-treatment after a time interval of 7-10 days as noted below is often recommended to eradicate any lice that hatched from nits after the initial treatment.
Medication treatment points
Over recent years, emerging resistance of lice to the most commonly used medications for treatment of infestation has been documented. This resistance has been noted in the United States as well as in countries in South America and Europe. The most resistance has been noted against permethrin and pyrethrin. In fact, studies have noted both genetic mutations and an increase in monooxygenase enzyme activity to increase resistance.
Studies have been showing that lice are more susceptible and treatment is more reliable with use of malathion. Malathion has been proving to be more ovicidal and have a higher lethal effect and decreased amount of reinfestation if used properly over permethrin. However, resistance to malathion is now starting to be reported in Great Britain.
Malathion resistance is thought to result from increased levels of carboxylesterases that (1) metabolize malathion into nonmalaoxon intermediates and (2) esterase sequestration of malathion and elevated metabolism by cytochrome P450 monooxygenases, glutathione, S-transferases, and phosphotriesterases. It is worth noting that the Great Britain formulations of malathion are different from the United States formulations. Malathion resistance has not been reported in the United States as of yet. This may be due to the difference in preparation. The United States formulation of malathion is coupled with isopropyl alcohol and terpineol, whereas the Great Britain formulation only contains malathion.
It is becoming evident that alternative medications or treatments will likely be needed to continue to treat lice effectively. New research incorporating treatment with ivermectin and trimethoprim/sulfamethoxazole are underway and may eventually show some promise for future treatment preparations. New nonpesticide and nonneurotoxic preparations, such as isopropyl myristate, may also eventually emerge as an alternative treatment modality.
Increasing emphasis is being placed on understanding the life cycle of lice in order to treat effectively. Not all treatment preparations are ovicidal. Therefore, repeat treatment may need to be performed to kill the newly hatched eggs not affected by the initial treatment. It is extremely important to use medications as directed to ensure total eradication of the lice through their life cycle.
The safety and effectiveness of benzyl alcohol lotion 5% was demonstrated in 2 multicenter, randomized, double-blind studies of 628 people, 6 months of age and older, with active head lice infestation. Individuals received two, 10-minute treatments of either benzyl alcohol lotion or topical placebo, 1 week apart. In these studies, the drug was effective in eradicating lice in 76.2% and 75% of subjects compared with placebo 4.8% and 26.2% respectively.1
With all treatments used to eliminate live lice, careful combing and removal of all nits from the hair as well as cleaning of other articles (ie, hair accessories, towels, bedding, clothing) are essential steps to prevent reinfestation.
Other treatment options
"Occlusive therapy" techniques such as vinegar, mayonnaise, petroleum jelly, olive oil, butter, isopropyl alcohol, and water submersion up to 6 hours have failed to be reliable methods of treatment.
Hair removal is one option to aid in blockade of propagation due to the need for the lice to lay their eggs on hair shafts. However, cosmetic results tend to make this option less appealing.
Scabicidal agents
Treatment options include permethrin 1% and 5% cream, pyrethrin products, lindane, mercuric oxide ointment 1%, and 0.5% malathion in 78% isopropanol.
For treatment failures, ivermectin—given orally in doses 1 week apart—may be used in the nonpregnant or nonbreastfeeding woman and in children weighing more than 15 kg.
One study reported efficacy of 4% dimeticone lotion (a silicone-based lotion believed to disrupt the louse's ability to manage water).2 Another study found that 4% dimeticone lotion was a significantly more effective treatment compared with malathion for most people.3
Permethrin 5% (Elimite) and 1% (Nix)
DOC recommended by most authorities. Permethrin is very effective in killing adult lice and nymphs but is not as effective in killing nits (eggs). A fine-toothed comb is an important adjunct to remove nits. Patients should wash hair with a nonmedicated shampoo.
Adult
Apply as a cream rinse, allow to remain in place for 10 min, then rinse off; a second application (using the same technique) is recommended 7-10 d after initial therapy to destroy nits effectively
Pediatric
Administer as in adults
None reported
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
May exacerbate redness, swelling, and itching, at least temporarily
Pyrethrin products (A200 Pyrinate, End Lice, RID Mousse, RID Shampoo)
Used in the treatment of Pediculus humanus infestations. The parasite absorbs the drug where its nervous system is stimulated, causing seizure and death to the parasite.
Adult
Apply as a cream rinse, allow to remain in place for 10 min, then rinse off; a second application (using the same technique) is recommended 7-10 d after initial therapy to destroy nits effectively
Pediatric
Administer as in adults
None reported
Documented hypersensitivity; chrysanthemum allergy
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Do not apply to eyes, face, or mucous membranes
Lindane 1% (Kwell)
Stimulates the nervous system of the parasite, causing seizure and death. Second-line treatment recommended for patients who fail to respond to permethrin or pyrethrin. Not very safe in children due to transcutaneous absorption leading to neurotoxicity. Overall, permethrin is a safer choice.
Adult
Apply as cream rinse after shampooing with nonmedicated shampoo; allow to remain in place for no more than 4 min, then rinse thoroughly
Pediatric
Apply as in adults
Oil-based hairdressings may increase toxicity of lindane
Documented hypersensitivity; neonates, patients with an acutely swollen skin, those diagnosed with Norwegian scabies
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution with history of seizures or keratinization/ichthyosis disorders; do not apply to eyes, face, or mucous membranes
Mercuric oxide ointment 1%
Used to treat louse infestation of eyelashes. Inspect eyelids for nits and remove them mechanically.
Adult
Apply to eyelashes qid for 14 d
Pediatric
Administer as in adults
None reported
Documented hypersensitivity
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Avoid direct contact with eye
Malathion (0.5%) in 78% isopropanol (Ovide Lotion)
Approved in 1999 by US FDA to treat head lice. Irreversible cholinesterase inhibitor that is hydrolyzed (and therefore detoxified) rapidly by mammals but not by insects; ovicidal and pediculicidal. Binds to hair and provides some residual protection after therapy.
Adult
Apply copious amounts of lotion to dry hair and massage; leave on 8-12 h, rinse, and remove nits with fine-tooth comb (repeat in 7-10 d if lice present)
Pediatric
<2 years: Not recommended
>2 years: Administer as in adults
None reported; however, potential exists for interaction with aminoglycosides and antimyasthenics
Documented hypersensitivity; contraindicated in neonates and infants because of increased transdermal absorption
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Contains flammable alcohol; do not expose lotion or wet hair to open flame or electric heat, eg, hair dryers (allow hair to dry naturally and uncovered following application); avoid contact with eyes (flush eyes immediately with water if contact)
Benzyl alcohol lotion
Benzyl alcohol inhibits lice from closing their respiratory spiracles, allowing the lotion to obstruct the spiracles, which ultimately results in asphyxiation. Does not elicit ovicidal activity. Contains 5% benzyl alcohol.
Adult
Apply lotion to dry hair, using enough to completely saturate scalp and hair; rinse off with water after 10 min; repeat treatment in 1 wk
Pediatric
<6 months: Do not use
>6 months: Apply as in adults
None reported
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
May cause irritation to skin, scalp, and eyes (avoid eye exposure and flush immediately with water if contact occurs); application site anesthesia and hypoesthesia may occur; serious adverse events (eg, respiratory distress, seizure, coma) and death with benzyl alcohol have been well documented in premature infants; IV administration of products containing benzyl alcohol has been associated with neonatal gasping syndrome consisting of severe metabolic acidosis, gasping respirations, progressive hypotension, seizures, CNS depression, intraventricular hemorrhage, and death in preterm, low birth weight infants; neonates (ie, <1 mo or preterm infants with a corrected age <44 wk) could be at risk for gasping syndrome if treated
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References
Benzyl alcohol lotion 5% [package insert]. Atlanta, GA: Sciele Pharma Inc; 2009. [Full Text].
Burgess IF, Brown CM, Lee PN. Treatment of head louse infestation with 4% dimeticone lotion: randomised controlled equivalence trial. BMJ. Jun 18 2005;330(7505):1423. [Medline].
Burgess IF, Lee PN, Matlock G. Randomised, controlled, assessor blind trial comparing 4% dimeticone lotion with 0.5% malathion liquid for head louse infestation. PLoS ONE. Nov 7 2007;2(11):e1127. [Medline].
American Academy of Pediatrics. Pediculosis. In: Pickering, LK ed. 2003 Red Book: Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Il: AAP; 2003:463-467.
Brown S, Becher J, Brady W. Treatment of ectoparasitic infections: review of the English-language literature, 1982-1992. Clin Infect Dis. Apr 1995;20 Suppl 1:S104-9. [Medline].
Clore ER, Longyear LA. A comparative study of seven pediculicides and their packaged nit removal combs. J Pediatr Health Care. Mar-Apr 1993;7(2):55-60. [Medline].
Drugs for head lice. Med Lett Drugs Ther. Jan 17 1997;39(992):6-7. [Medline].
Gilbert DN, Moellering RC, Jr., Samde MA. The Sanford Guide to Antibiotic Therapy 1998. Dallas, Tex: Antimicrobial Therapy Inc; 1998:94-95.
Halpern JS. Recognition and treatment of pediculosis (head lice) in the emergency department. J Emerg Nurs. Apr 1994;20(2):130-3. [Medline].
Hart G. Risk profiles and epidemiologic interrelationships of sexually transmitted diseases. Sex Transm Dis. May-Jun 1993;20(3):126-36. [Medline].
Heukelbach J, Feldmeier H. Ectoparasites--the underestimated realm. Lancet. Mar 13 2004;363(9412):889-91. [Medline].
Huynh TH, Norman RA. Scabies and pediculosis. Dermatol Clin. Jan 2004;22(1):7-11. [Medline].
Ibarra J, Hall DM. Head lice in schoolchildren. Arch Dis Child. Dec 1996;75(6):471-3. [Medline].
Klaus S, Shvil Y, Mumcuoglu KY. Generalized infestation of a 3 1/2-year-old girl with the pubic louse. Pediatr Dermatol. Mar 1994;11(1):26-8. [Medline].
Kristensen M, Knorr M, Rasmussen AM, et al. Survey of permethrin and malathion resistance in human head lice populations from Denmark. J Med Entomol. May 2006;43(3):533-8. [Medline].
Lebwohl M, Clark L, Levitt J. Therapy for head lice based on life cycle, resistance, and safety considerations. Pediatrics. May 2007;119(5):965-74. [Medline].
Mumcuoglu KY, Meinking TA, Burkhart CN, et al. Head louse infestations: the "no nit" policy and its consequences. Int J Dermatol. Aug 2006;45(8):891-6. [Medline].
Yoon KS, Gao JR, Lee SH, et al. Permethrin-resistant human head lice, Pediculus capitis, and their treatment. Arch Dermatol. Aug 2003;139(8):994-1000. [Medline].
Further Reading
Keywords
lice, louse, nits, pediculosis capitis, head lice, pediculosis corporis, body lice, pediculosis pubis, pubic lice, crabs, Pediculus humanus capitis, Pediculus humanus corporis, Pthirus pubis, lice infestation
