Permethrin in Pregnancy and Breastfeeding

Risk Factor: BM
Class: Anti-infectives / Scabicides/pediculicides

Contents of this page:
Fetal Risk Summary
Breast Feeding Summary
References
Questions and Answers

Fetal Risk Summary

Permethrin, a pyrethroid, is indicated for the topical treatment of Sarcoptes scabiei (scabies) infestations. The drug is also active against lice, ticks, fleas, mites, and other arthropods. In patients with moderate to severe scabies, systemic absorption was estimated to be 2% or less of the dose (1,2).

Oral reproduction studies with permethrin have been conducted in mice, rats, and rabbits at doses of 200400 mg/kg/day (1,2). No adverse effects on fertility or evidence of fetal harm were observed in these studies. Species-specific carcinogenesis was observed in mouse studies but negative results were seen in rats. Genetic toxic studies revealed no evidence of mutagenicity (1,2). Only the highest oral concentrations (25004000 ppm) of permethrin administered after implantation were found to significantly lower the protein and glycogen contents of rat placentas, but this had no statistical effect on the number of live fetuses (3).

Although no studies of permethrin placental transfer have been located, the molecular weight (about 391) is low enough that transfer should occur. However, because only small amounts are absorbed systemically and this is rapidly metabolized by ester hydrolysis to inactive metabolites, the opportunity for fetal exposure to permethrin appears to minimal, if it occurs at all.

A 1995 case report described the use of multiple courses of permethrin and other agents in a pregnant woman who had developed crusted scabies (4). She was initially treated at 2 months' gestation with monosulfiram (a pesticide not available in the United States). Relapse occurred at 5 months' gestation and she was treated with two total body (24 hour) applications of malathion 0.5% liquid and one total body (24 hour) application of monosulfiram 25% solution. Three weeks later another relapse occurred and she was treated with permethrin 5% cream to the whole body for 12 hours. Because live mites were found the next day, a sulfur/tar/coconut oil soak to the scalp three times daily followed by two total body benzyl benzoate 25% treatments within 24 hours. Then permethrin cream was used weekly for 3 weeks. A healthy male infant was delivered at term (4).

The Centers for Disease Control and Prevention (CDC) considers permethrin or pyrethrins with piperonyl butoxide to be the treatments of choice for pubic lice in pregnant women (5). Although not specifically mentioned, permethrin or pyrethrins with piperonyl butoxide should also be used if other body areas of a pregnant woman, such as the head, are infested with lice. For pregnant women with scabies, permethrin is considered the treatment of choice in the United States and the United Kingdom (5,6).

Breast Feeding Summary

No reports describing the use of topical permethrin during lactation have been located. Although the molecular weight (about 391) is low enough for excretion into breast milk, the minimal systemic absorption and rapid metabolism suggests that little, if any, of the drug will be found in milk. The CDC considers permethrin or pyrethrins with piperonyl butoxide to be the treatment of choice for pubic lice during lactation (5). For lactating women with scabies, permethrin is considered the treatment of choice in the United States and the United Kingdom (5,6).

References

  1. Product information. Elimite. Allergan, 2001.
  2. Product information. Acticin. Bertek Pharmaceuticals, 2001.
  3. Spencer F, Berhane Z. Uterine and fetal characteristics in rats following a post-implantational exposure to permethrin. Bull Environm Contam Toxicol 1982;29:848.
  4. Judge MR, Kobza-Black A. Crusted scabies in pregnancy. Br J Dermatol 1995;132:1169.
  5. CDC. 1998 Guidelines for treatment of sexually transmitted diseases. MMWR 1998;47:1116.
  6. Clinical Effectiveness Group (Association of Genitourinary Medicine and the Medical Society for the Study of Venereal Diseases). National guideline for the management of scabies. Sex Transm Inf 1999;75 (Suppl):S767.

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Questions and Answers

Why does a person have to wait at least 7 days before using permethrin cream again?, If a person has scabies and uses a permethrin cream like nix to get rid of it, and it becomes obvious several days later that there are still some scabies left, why do they have to wait at least 7 days before they can use the permethrin cream again?

to avoid poisoning themselves.

Are scabies still contagious with the use of Permethrin cream?, I recently went to Venice about two weeks ago and caught scabies either at the beach or the hotel I stayed at...My mom got a prescription for Permethrin Cream 5% and this is now my second day with the treatment....My only concern is my sister's baby lives in the house with us and even though he has no signs of it can I still give him scabies with the treatment on? (We're still taking him to the doctor to get treated with a less harmful cream)

Yes, scabies is contagious until it is gone and some scabies mites are showing signs of being immune to permethrin and other chemical solutions.

Additionally, permethrin has been shown to cause tumours in lab rats and even more severe in yournger rats so fit the baby shows signs of scabies, please be careful in using it on him.

you may want to get something to use to spray onto yoru furniture and use in your laundry that is chemical free but works on scabies like Kleen-Free.

This is a chemical free solution that works to break down the exoskeleton of the mite. They can tell you how much to use in the laundry online.

Good luck getting rid of it and if the permethrin is not working for you, maybe the ones you have are chemical rsistent and you may also need to look at the Kleen-Free stuff. Apparently it works very well.

What is the strongest imaginable PERMETHRIN concentrate available on the market today?, I have a stable and a trillion flies, how do i get rid of them?

No, it's not the strongest!! That thinking doesn't work and ends up in the insect becoming resistant to the chemical.

http://www.ipm.ucdavis.edu/PMG/PESTNOTES...

read: repeated applications during fly season

How often should you use permethrin 5% cream for scabies?, I've applied two treatments one week apart, and my skin improved but has now taken a turn for the worse again. I applied two more treatments this week and revacuumed/washed everything. I've had scabies for 4-5 months now; is this common to have to repeat this much and in using it so frequently does this inhibit the cream's ability to kill the mites?

The cream will do nothing but kill the eggs. As bad as it sounds, when I had scabies I slept on a recliner and washed it daily until I knew I was clean. The permethrin worked for me the first time and I belive I was on the 3rd egg cycle so I think you might be not sterilizing in the best ways. Good Luck, I feel your pain...if it makes you feel any better look up the history of scabies. It used to be called the 7 year itch before proper medicine....I could only imagine back in those days...

How long do I have to keep my dogs seperate from my cats after treating the dogs with permethrin?, I got some Advantix at the pet store and was told to keep my cats away from the dogs after I apply it but not for how long. I went online and am frightened to learn the high toxicity of the main ingredient to cats. I already put the stuff on the dogs this morning and I have left them outside but now I am afraid to let them back in. How long is it before it is safe for them to be around my cats again...will it help if I bathe the dogs??

it will help to bathe the dogs, after that, they should be fine with the cats.

What is the difference between pyrmethrin and permethrin?, Are they the same substance and just different spelling?

I think they can be used as a mosquito repellent on nets and clothes

Perhaps you mean pyrethrum which is a natural product from
a flower. Permethrin is a synthetic chemical. Permethrin is more stable so works better but both good insecticides. The chemical structures are simillar but can't draw here.

How much does Permethrin 5% typically cost w/o Health Insurance?, I am definitely sure I have scabies. So I need to get a prescription for Permethrin. However, I do not have health insurance. I am sure the doctor visit will cost some, but how much does Permethrin 5% (Such as Elimite, Acticin) typically cost?

The cost of rx depends on dosage and where you are
buying. Mail order is the least expensive. If you get the
eHealthPlus membership, you could save to 70%.

After using permethrin cream for Crabs do the dead nits have to be removed?,

After you put it on and wait "x" number of hours, you just shower and they should come out. Make sure to wash all your bedding in hot water, vaccum the room VERY well, wash all clothing, etc.

How long does it take for the scabies rash to go away once I've treated it with Permethrin cream?, I've already used the cream for three nights, I'm no longer itching but I still have the bumps.

You should only use the cream once a week for a total of 2 weeks.
Anyways, even after u have killed the parasites, it still takes time for wounds to heal. So I'm guessin that it'll get better over the days but it will be completely gone in 2-3 weeks.

And by the way, it's normal for yourself to be itchy and get new bumps after treatment because the dead mites are still there. It's pretty much a scabies graveyard under your skin, which still causes reactions in ure body to make even more bumps. This all goes away in a few weeks, usually along with ure bumps, unless of course you scratch them to much.

When using the pesticide "permethrin" on leaf lettuce, how long should you wait to harvest and/or eat?,

go to site safe2use.com permethrin is used on wheat and cotton,corn it will tell you more about permethrin and children are affected more than adults. good luck