Drugs List

Therapeutic Indications

Uses

Head lice

Contraindications

None known

Precautions and Warnings

Children under 3 years
Breastfeeding
Pregnancy

Avoid contact with eyes
Do not apply to broken or secondarily infected skin
If accidental contact with the eyes occurs, rinse thoroughly with water
Treatment may affect permed, pre-rinsed, bleached or coloured hair
Advise patient to consult a doctor if symptoms persist despite treatment
Advise patient to seek medical attention if persistent irritation occurs

When treating permed or coloured hair the manufacturers advise performing a patch test before use on the entire scalp.
In patients with hypersensitivity to chrysanthemums, treatment should be switched to a chemically different agent, unless treatment is strictly indicated.

Pregnancy and Lactation

Pregnancy

Use permethrin with caution during pregnancy.

Briggs suggests neither the animal data or limited human pregnancy data suggest risk for the embryo or the foetus. The manufacturers suggest use of permethrin during pregnancy may be only considered when treatment is clearly needed.

Limited data is available for the use of permethrin during human pregnancy.

Reproduction studies performed in animals using oral preparations revealed no impaired fertility or hazard to the foetus.

The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Lactation

Use permethrin with caution in breastfeeding.

The Drugs and Lactation database (LactMed) suggests because permethrin is metabolised to inactive metabolites rapidly and less than 2% is absorbed after topical application, topical permethrin is acceptable in breastfeeding. The manufacturer suggests, whilst it is unlikely that the concentrations of permethrin in breast milk will present any risk to the infant, consideration should be given to withholding treatment or temporarily discontinuing breastfeeding.

Animal studies following oral administration indicate that very low concentrations of permethrin are excreted in the breast milk. It is not known if permethrin is excreted in human milk. The low molecular weight (about 391) is low enough for excretion into breast milk but the minimal systemic absorption and rapid metabolism suggests that little, if any, of the drug will be found in milk.

Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1

Side Effects

Erythema
Irritation (localised)
Paraesthesia
Rash

Presentation

Topical solutions containing permethrin.

Drugs List

Therapeutic Indications

Uses

Head lice

Dosage

Apply to the hair after washing and towel-drying hair, paying particular attention to behind the ears and nape of neck. Leave on for 10 minutes and then rinse and dry as usual.

No maximum dose has been defined but use of more than 2 bottles (118ml) is unlikely for any one course of treatment. One bottle (59ml) should be sufficient for shoulder length hair of average thickness.

It is not necessary to remove dead eggs or nits, however for cosmetic purposes a fine toothed comb may be used if desired.

Residual activity may persist for up to six weeks.

Children

Contraindications

None known

Precautions and Warnings

Children under 3 years
Breastfeeding
Pregnancy

Avoid contact with eyes
Do not apply to broken or secondarily infected skin
If accidental contact with the eyes occurs, rinse thoroughly with water
Treatment may affect permed, pre-rinsed, bleached or coloured hair
Advise patient to consult a doctor if symptoms persist despite treatment
Advise patient to seek medical attention if persistent irritation occurs

When treating permed or coloured hair the manufacturers advise performing a patch test before use on the entire scalp.
In patients with hypersensitivity to chrysanthemums, treatment should be switched to a chemically different agent, unless treatment is strictly indicated.

Pregnancy and Lactation

Pregnancy

Use permethrin with caution during pregnancy.

Briggs suggests neither the animal data or limited human pregnancy data suggest risk for the embryo or the foetus. The manufacturers suggest use of permethrin during pregnancy may be only considered when treatment is clearly needed.

Limited data is available for the use of permethrin during human pregnancy.

Reproduction studies performed in animals using oral preparations revealed no impaired fertility or hazard to the foetus.

The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Lactation

Use permethrin with caution in breastfeeding.

The Drugs and Lactation database (LactMed) suggests because permethrin is metabolised to inactive metabolites rapidly and less than 2% is absorbed after topical application, topical permethrin is acceptable in breastfeeding. The manufacturer suggests, whilst it is unlikely that the concentrations of permethrin in breast milk will present any risk to the infant, consideration should be given to withholding treatment or temporarily discontinuing breastfeeding.

Animal studies following oral administration indicate that very low concentrations of permethrin are excreted in the breast milk. It is not known if permethrin is excreted in human milk. The low molecular weight (about 391) is low enough for excretion into breast milk but the minimal systemic absorption and rapid metabolism suggests that little, if any, of the drug will be found in milk.

Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1

Side Effects

Erythema
Irritation (localised)
Paraesthesia
Rash

Overdosage

It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

The following number will direct the caller to the relevant local centre (0844) 892 0111

Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Further Information

Last Full Review Date: October 2013

Reference Sources

Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.

Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press [Accessed on October 14, 2013].

Paediatric Formulary Committee. BNF for Children (online) London: BMJ Group, Pharmaceutical Press, and RCPCH Publications [Accessed on October 14, 2013].

Summary of Product Characteristics: Lyclear Creme Rinse. Omega Pharma Ltd. Revised August 2018.
Summary of Product Characteristics: Lythrin 1% Creme Rinse. Ovelle Ltd. Revised June 2007

US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
Available at: https://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
Permethrin. Last revised: September 7, 2013
Last accessed: October 14, 2013.