What is the dose of Nix (permethrin)?

Permethrin (Nix) Dosing Guidelines

Permethrin 1% creme rinse (Nix) should be applied to affected areas and washed off after 10 minutes for the treatment of head lice or pubic lice. 1, 2

Dosing by Indication

Head Lice (Pediculosis Capitis)

• Apply permethrin 1% creme rinse to hair and scalp
• Leave on for 10 minutes
• Rinse thoroughly with water
• A single application is typically effective, but a second application 7-10 days after the first treatment may be needed to kill newly hatched lice 2

Pubic Lice (Pediculosis Pubis)

• Apply permethrin 1% creme rinse to affected areas
• Leave on for 10 minutes
• Rinse thoroughly with water 1

Scabies

• For scabies, a higher concentration is used: permethrin 5% cream
• Apply to all areas of the body from the neck down
• Leave on for 8-14 hours before washing off 1, 3
• Usually 30 grams is sufficient for an average adult 3
• One application is generally curative 3

Efficacy and Safety Considerations

• Permethrin 1% has demonstrated superior efficacy compared to other treatments:

  • 99% of patients were lice-free at 14 days with permethrin 1% compared to 85% with lindane 1% shampoo 4
  • In another study, permethrin showed 97% cure rate compared to only 6% for placebo 5

• Safety profile:

  • Systemic absorption following topical application is very low 6
  • Elimination is virtually complete after one week 6
  • Adverse effects are infrequent, mild, and usually difficult to distinguish from symptoms of the infestation itself 4

Important Clinical Pearls

• Persistent itching after treatment is common and rarely indicates treatment failure; it is not an indication for retreatment 3
• Retreatment is only necessary if live mites/lice are found after 14 days 3
• For head lice, treatment should be confirmed by finding no live lice using a fine-toothed louse comb 2
• Environmental measures:
  • Bedding and clothing should be decontaminated by machine-washing or machine-drying using the heat cycle, or dry-cleaning 1
  • Alternatively, items can be removed from body contact for at least 72 hours 1
  • Fumigation of living areas is not necessary 1

Special Populations

• Pregnant and lactating women can safely use permethrin 1% for lice treatment 1
• For pediculosis of the eyelashes, do not apply permethrin directly to eyes; instead, use occlusive ophthalmic ointment to the eyelid margins twice daily for 10 days 1
• HIV-infected patients with pediculosis should receive the same treatment regimen as HIV-negative individuals 1

Permethrin 1% creme rinse offers an excellent balance of high efficacy with low toxicity for the treatment of lice infestations, making it a first-line treatment option 5.