Permethrin (Nix)

1. Health Canada Product Monograph — Permethrin

• Permethrin 5% cream is used to treat scabies infestation caused by the mite Sarcoptes scabiei.
• Permethrin 1% crème rinse is used to treat head lice infestation and their eggs (nits).

• Animal studies with oral permethrin doses far higher than typical topical human exposure showed no evidence of harm to the fetus.
• There are no adequate, well-controlled studies of permethrin in pregnant women, so it should be used during pregnancy only after consulting a healthcare professional.

• It is not known whether permethrin passes into human breast milk.
• Because of limited safety data, a healthcare professional should be consulted before using permethrin while breastfeeding.

• Adults over 70 should be treated under medical supervision, since scabies can occasionally involve the scalp, face, and ears in older adults, requiring a wider application area.

• Permethrin 5% cream is approved for children 2 years of age and older; safety and effectiveness under 2 years have not been established.
• Permethrin 1% crème rinse is approved for children 2 years of age and older; it should not be used in children under 2.
• Children should be supervised by an adult during application to ensure thorough treatment.
• Clinical studies that included infants as young as two months found no meaningful differences in side effects between children and adults.

• For scabies, adults and children over 12 apply approximately one 30 g tube of permethrin 5% cream to the entire body (excluding the head and face in most adults), left on for 8 to 14 hours before washing off.
• For scabies in children 5 to 12 years, about half a tube (15 g) is used; for children 2 to 4 years, about a quarter tube (7.5 g) is used, applied the same way.
• A second scabies application may be given 7 to 10 days after the first, but only if live mites are still seen or new lesions appear.
• For head lice, permethrin 1% crème rinse is applied to freshly shampooed (conditioner-free), towel-dried hair, left on for 10 minutes, then rinsed off with water; a fine-tooth comb is then used to remove nits.
• A second head lice application is recommended only if live lice or nits are still seen on or after day 7.
• Close contacts and household members should also be checked and treated at the same time if infested, to prevent reinfestation.
• Clothing, bedding, and towels used within two days before treatment should be machine washed in hot water and dried on high heat for at least 20 minutes, or dry cleaned, and combs or brushes should be disinfected in hot water.

If overdose is suspected, seek emergency medical attention immediately or contact your regional Poison Control Centre without delay.

• Overdose of permethrin most often occurs from accidental or deliberate swallowing rather than from topical use, since less than 2% of a topical dose is absorbed through the skin.
• Symptoms of overdose may include dizziness, loss of appetite, nausea, vomiting, headache, weakness, seizures, and loss of consciousness.
• Treatment of overdose is supportive; symptomatic care should be given for any hypersensitivity-type reaction.

• Burning sensation at the application site may occur.
• Stinging at the application site may occur.
• Tingling at the application site may occur.
• Itching (pruritus) may occur and can persist for one to several weeks after treatment as the body reacts to dead mites; this does not mean the treatment has failed.
• Redness (erythema) of the skin may occur.
• Mild rash may occur.
• Small raised bumps (papules) may occur.
• Skin swelling (oedema) may occur.
• An eczema-like skin reaction may occur.
• Numbness or a "pins and needles" sensation (paraesthesia) may occur.
• Scalp irritation may occur with the crème rinse formulation used for head lice.
• Skin pain or tenderness may occur rarely.
• Mild diarrhea has been reported rarely with topical use.

Serious side effects require immediate discussion with the prescriber or emergency care.

• Allergic reactions, including hives, marked swelling, or difficulty breathing, can occur, particularly in people sensitized to chrysanthemums or other pyrethroids.
• Eye contact can cause marked irritation, even though permethrin itself is not considered a primary eye irritant, since other ingredients in the product may cause this.
• Persistent or worsening skin irritation that does not improve should be evaluated by a doctor.
• Treatment failure with recurrent live infestation can occur if the product is not applied for the full recommended contact time or to the full recommended area.
• Seek medical attention right away for facial or throat swelling, widespread hives, or difficulty breathing, which may signal a severe allergic reaction.

• Use with caution in patients with widespread or broken skin, since increased absorption may raise the risk of systemic side effects.
• Use with caution near the eyes, mouth, nose, and mucous membranes, avoiding contact with these areas entirely during application.
• Caregivers who routinely apply permethrin to others may wish to wear gloves to avoid hand irritation.
• Use with caution in patients with known sensitivity to other pyrethroid- or pyrethrin-containing products.
• Use with caution in infants and young children, since the 5% cream is not authorized under 2 years of age and full-body application increases relative exposure.
• Use with caution in patients with severe or widespread scabies, who are more likely to experience skin discomfort after application.

• Contraindicated in patients with known hypersensitivity to permethrin or other pyrethroids/pyrethrins.
• Contraindicated in patients with known hypersensitivity to chrysanthemums.
• Not for use on mucous membranes, the eyes, or broken or infected skin.

• No systemic drug interactions have been established for topical permethrin, since absorption through intact skin is minimal.
• Corticosteroid treatment of eczema-like skin reactions should be withheld until permethrin treatment is complete, since it may blunt the immune response needed to clear the infestation.
• Other topical medications, steroid creams, and cosmetics applied to the treatment area should be discontinued before starting permethrin, to avoid interfering with its effectiveness.
• Use of hair conditioner before applying permethrin crème rinse can reduce its effectiveness against lice and should be avoided.

• Permethrin is applied to the skin or hair rather than taken by mouth, so food timing does not apply.

• Permethrin is applied topically as directed for scabies or head lice treatment and is not tied to meal times; the key timing consideration is how long the product is left on the skin or hair before rinsing.

• Store permethrin cream and crème rinse at 15°C to 25°C.
• Keep out of reach of children, and discard any unused product after use to prevent accidental ingestion.

• Permethrin treats scabies with the 5% cream and head lice with the 1% crème rinse, by killing the mites or lice and their eggs.
• Apply exactly as directed, covering the full recommended area and time, since incomplete treatment is a common cause of failure.
• Treat close contacts and household members at the same time to prevent reinfestation.
• Wash clothing, bedding, and towels in hot water and dry on high heat to eliminate mites or lice from fabric.
• Itching can continue for a few weeks after successful treatment and does not by itself mean the treatment failed; contact a healthcare professional if symptoms worsen or new lesions appear.