What is the treatment for a patient with pubic lice (Pthirus pubis)?

Treatment of Pubic Lice (Pediculosis Pubis)

Treat pubic lice with permethrin 1% cream rinse applied to affected areas and washed off after 10 minutes, or alternatively pyrethrins with piperonyl butoxide applied and washed off after 10 minutes. 1

First-Line Treatment Options

The CDC provides three equally acceptable first-line regimens for pubic lice 1:

• Permethrin 1% cream rinse: Apply to affected areas and wash off after 10 minutes 1
• Pyrethrins with piperonyl butoxide: Apply to affected area and wash off after 10 minutes 1
• Lindane 1% shampoo: Apply for 4 minutes then thoroughly wash off—this is the least expensive option but has important contraindications 1

Permethrin has less potential for toxicity than lindane in the event of inappropriate use, making it the safer choice when cost is not prohibitive. 1

Critical Contraindications

Never use lindane in the following populations 1, 2:

• Pregnant or lactating women 1
• Children less than 2 years of age (some sources recommend avoiding in children under 10 years) 1, 2
• Patients with extensive dermatitis 1
• Never apply lindane after a bath 1

For pregnant and lactating women, use only permethrin or pyrethrins with piperonyl butoxide 1.

Alternative Regimens for Treatment Failure

If first-line therapy fails 1, 2, 3:

• Malathion 0.5% lotion: Apply to affected areas and rinse after 8-12 hours 2, 3
• Oral ivermectin 250 μg/kg: Repeat after 2 weeks (note: limited ovicidal activity requires the second dose) 2, 3

Increasing resistance to permethrin and pyrethrins has been reported, making malathion a reasonable option when therapeutic failure due to resistance is suspected 2.

Special Considerations for Eyelash Involvement

Never apply topical pediculicides to the eyes. 1, 2

For pediculosis of the eyelashes 1, 2:

• Apply occlusive ophthalmic ointment (petrolatum, erythromycin, or bacitracin) to eyelid margins 2-3 times daily for 10 days 1, 2
• Manual removal of lice and nits using tweezers may be necessary 2
• For adherent nits, epilation of involved eyelashes may be required 2

Essential Environmental and Contact Management

Environmental decontamination is crucial for preventing reinfestation 1, 2:

• Machine wash or machine dry bedding and clothing using the heat cycle, or dry-clean 1
• Alternatively, remove items from body contact for at least 72 hours 1
• Fumigation of living areas is not necessary 1

All sexual partners within the preceding month must be treated 1, 2, and patients should be evaluated for other sexually transmitted infections 4, 5.

Follow-Up Protocol

Evaluate patients after 1 week if symptoms persist 1, 2. Re-treatment is necessary if 1:

• Live lice are found, or
• Eggs are observed at the hair-skin junction

Patients not responding to one recommended regimen should be retreated with an alternative regimen. 1

Approximately 75% of patients who continue to have pruritus at 2 weeks will have resolution by 4 weeks, as treatment may temporarily exacerbate itching, edema, and erythema 6.

Common Pitfalls to Avoid

• High failure rates occur with single treatments: One study showed 40-43% of patients remained infested after single treatment with either lindane or permethrin, suggesting a second treatment at 10 days may be beneficial 7
• Pruritus persistence does not always indicate treatment failure: Itching may continue for several weeks after successful eradication due to hypersensitivity reactions 6
• HIV-infected patients receive the same treatment as those without HIV infection 1