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Malathion aqueous liq 0.5%

Updated 2 Feb 2023 | Topical parasiticides


Liquid emulsion formulation of malathion

Drugs List

  • DERBAC -M 0.5% liquid
  • malathion aqueous 0.5% liquid
  • Therapeutic Indications


    Head lice
    Pubic lice


    Treatment should be repeated after 7 days.


    Treatment of head lice
    Rub malathion liquid into scalp and hair until thoroughly moistened and leave to dry naturally for a minimum of 12 hours but preferably until the next day. Shampoo hair in the normal way, rinse and comb whilst wet to remove dead lice and eggs (nits) using a fine toothed nit comb.

    Treatment of crab (pubic) lice
    Apply malathion liquid to whole body surface area, paying particular attention to hairy areas like beards and moustaches. All surfaces of the body should be treated including the scalp, neck and face. Allow to dry naturally.
    Leave on for at least one hour but preferably overnight, before washing off in the usual manner.

    Treatment of scabies
    In the treatment of scabies, family members and close contacts should be treated simultaneously.
    Apply malathion liquid to whole body surface area including the scalp, neck, face and outer ears and allow to dry naturally.
    Do not wash off or bathe for 24 hours. If hands or other areas are washed, the treatment must be reapplied immediately.
    No special sterilisation of clothing is required. Ordinary laundry / dry clean with a hot iron press is sufficient.
    The itch and rash may persist for some weeks after treatment.


    (See Dosage; Adults).


    Children over 6 months
    (See Dosage; Adults).

    Children aged 6 months and under
    Malathion liquid should be used under medical supervision only.

    Additional Dosage Information

    Malathion liquid should be used not more than once a week and for not more than 3 consecutive weeks.


    None known

    Precautions and Warnings

    Children under 6 months

    Avoid contact with eyes, lips or mouth
    Breastfeeding: Wash product off breasts prior to breastfeeding infant
    Do not apply to broken or secondarily infected skin
    Scabies - treat family and close contacts simultaneously
    Scabies- use anti-irritant cream if rash & itching persist after treatment.
    Medical supervision required for infants under 6 months
    Do not use more than once a week or for longer than 3 weeks at a time.

    If applied to the breast area, the area should be washed and dried prior to breastfeeding and the preparation applied afterwards.

    Use gloves when treating large numbers of patients.

    Pregnancy and Lactation


    Use malathion with caution in pregnancy.

    Exposure to organophosphorous pesticides should be avoided in pregnancy wherever possible. Occupational or environmental exposure to malathion at or below accepted safety limits is unlikely to produce a substantial teratogenic risk, but the data are insufficient to state that there is no risk. Nevertheless, when there has been significant exposure, this is not an indication for the termination of pregnancy. However, if the mother has had symptoms of toxicity and/or continuous exposure, she may be offered additional prenatal diagnostic measures, e.g. a detailed foetal ultrasound (Schaefer, 2007).

    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 ( ) or if this is unavailable at the backup site ( ).


    Use malathion with caution in lactation.

    Malathion appears to be poorly absorbed after topical application, so it is not likely to reach the breast milk in large amounts. However, breast milk excretion of malathion has not been studied after application of 0.5% lotion. Until more data becomes available, an alternate agent is preferred.

    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

    Side Effects

    Chemical burns
    Hypersensitivity reactions
    Skin irritation
    Swollen eyes


    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 ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: January 2016

    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.

    Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press Accessed on 14 January 2016.

    Paediatric Formulary Committee. BNF for Children (online) London: BMJ Group, Pharmaceutical Press, and RCPCH Publications Accessed on 14 January 2016.

    Summary of Product Characteristics: Derbac M Liquid. G R Lane Health Products Ltd. Revised March 2015.

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Malathion Last revised: 15 May 2015
    Last accessed: 14 January 2016

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