Click here for an explanation of these scores
Answer Rating key
|
search
|
|
strong
|
|
appraisal
|
|
weak
|
|
confidence
|
|
moderate
|
Question answered:16/07/08
Prodigy state that (1):
"In pregnancy and breastfeeding the National Teratology Information Service currently recommend malathion because it is poorly absorbed and rapidly eliminated. A single application should be used where possible. If a single dose is ineffective, a second application could be considered after an interval of at least 7 days (telephone 0191 232 1525 for further information) [Personal Communication, National Teratology Information Service, 2001]."
We contacted the National Teratology Information Service who provided us with further comment. In their communication they state:
"There are few published data available to assess the potential fetotoxicity of topical preparations used to treat scabies and headlice during pregnancy.
Malathion
In general, when OPs are used in the recommended way they have not been associated with fetal toxicity in either animal reprotox studies or human pregnancy. In high concentrations OPs can inhibit cholinesterase, which may result in toxic symptoms requiring hospitalisation. The severity of the toxicity in the mother and fetus is likely to be dose related. However, in the absence of severe maternal toxicity it is unlikely that there will be any increased risk of fetal toxicity.
Malathion 0.5% is the agent of choice for the treatment of scabies and head lice. It is poorly absorbed following topical application, and is rapidly metabolised by the body. This concentration of malathion is designed to kill the lice, and not cause toxicity in the mother or fetus.
Provided that there is no family history of malformations or poor obstetric history the risk of fetal toxicity following maternal application of malathion 0.5% is likely to be no greater than that for the general population.
Permethrin
There are no controlled studies of the use of permethrin in human pregnancy. However, low toxicity for human subjects has been reported following pyrethroid exposures. Animal studies using high dose applications did not show an increased incidence of mutagenic or teratogenic effects.
The National Teratology Information Service (NTIS) in the UK has prospective follow-up data on the outcome of pregnancy in 21 women exposed to pyrethroid pesticides during pregnancy. There were 17 normal babies, 1 spontaneous abortion (no post-mortem data available, cause-effect relationship not established) and 3 children with anomalies.
The anomalies were: 1 infant exposed at 7 weeks pregnancy had mild talipes which had resolved by three months of age; 1 infant exposed at 16 weeks, was delivered spontaneously at 34 weeks and had a small unilateral inguinal hernia (causal relationship is most doubtful); 1 infant exposed at 37 weeks was a full-tem breech delivery and had an abnormal right little toe. Exposure at 37 weeks could not have been responsible for this anomaly as digit development is usually complete by 51 days of gestation.
It is unlikely that there will be an increased risk of congenital malformation or other types of fetal toxicity (e.g. spontaneous abortion, IUGR) associated with topical permethrin use. When used in the recommended way, it is only in contact with the skin for a short time and less than 2% of dose is systemically absorbed. In the absence of severe maternal toxicity it is most unlikely that exposure to pyrethroids would cause fetal damage. Provided that there is no family history of malformations or poor obstetric history the risk of fetal toxicity following maternal application of permethrin is likely to be no greater than that for the general population."
: Permethrin is a pyrethrin (pyrethrums) insecticide derived from dried chrysanthemum flowers. The pyrethrins are widely used as both domestic and agricultural insecticide sprays and dusting powders. They have also been used in topical preparations for the treatment of pediculosis.: Malathion is an organophosphate (OP) insecticide. Environmental or occupational exposure to Malathion at, or below accepted safety limits, is unlikely to cause an increased risk of maternal or fetal toxicity. No significant increase in the incidence of congenital malformations was reported in a cohort study of 22,465 infants born to women who lived in areas where aerial malathion spraying had occurred during the first trimester. Similar results were reported from a case control study of 722 offspring whose mothers lived in areas where spraying occurred during pregnancy.
A section in Therapeutics in pregnancy and lactation concurs that there is a lack of data on the effects of headlice and scabies treatments on the fetus but adds that malathion is first choice in pregnancy. It notes that aqueous preparations are preferable to the alcoholic lotions and that women should be advised not to exceed the recommended dose or use the preparations repeatedly (2).
1. Prodigy guidance, Scabies, http://www.prodigy.nhs.uk/guidance/CRs/Scabies.htm
2. Lee, Inch, Finnigan, Therapeutics in Pregnancy and Lactation, Radcliffe Medical Press 2000.
DISCLAIMER: TRIPanswers is a collection of clinical questions and answers. Each provider will have their own methodology in answering questions and these are likely not to be as rigorous as systematic review. If you have any doubt as to the implications of this contact the Q&A Service Provider for further information. This document is presented for information purposes only. This document cannot and should not be used as a basis of diagnosis or choice of treatment, and is in no way intended to replace professional medical care or attention by a qualified practitioner. TRIPanswers and TRIP Database Ltd are not responsible or liable for, directly or indirectly, ANY form of damage whatsoever resulting from the use/misuse of information contained in or implied by this document. Also, ensure you have read the terms and conditions for using the site.