Pyrethrum Extract and Piperonyl Butoxide, Topical Route

Designed to treat various different types of lice, pyrethrum extract and piperonyl butoxide is a topical treatment which can be purchased without a prescription.

Overview

Pyrethrum extract and piperonyl butoxide is a topical treatment for lice. It is absorbed by the lice and acts on their nervous systems to kill them. It does not harm humans in the same way and has a very minimal effect on the human body in general. It is a very common treatment for head lice, pubic lice (often called crabs) and other lice found on the body.

Pyrethrum extract is a common ingredient in pesticides, and in this topical treatment it is the active ingredient responsible for destroying the lice. Piperonyl butoxide doesn't have pesticide properties itself, but it is also commonly included in insect killing products because it is a synergist. Synergists work by slowing down or stopping the breakdown of pesticide chemicals in the pests themselves. Essentially, piperonyl butoxide makes pyrethrum extract more toxic and therefore more efficient in destroying lice.

This drug is available without a doctor’s prescription and can be purchased over the counter (OTC). It is available in a variety of dosage forms, including:

  • Shampoo
  • Liquid
  • Gel/Jelly
  • Foam
  • Kit

In the US, pyrethrum extract and piperonyl butoxide is available under the following brand names:

  • A200 Maximum Strength and A200 Time-Tested Formula
  • Lice-X
  • Licide
  • Medi-Lice Maximum Strength
  • Pronto Maximum Strength
  • Pyrinex
  • Pyrinyl
  • Rid
  • Tisit

Conditions Treated

  • Lice

Type of Medicine

  • Pediculicide

Side Effects

Most people do not experience any side effects when using pyrethrum extract and piperonyl butoxide, but in rare instances the following can occur:

  • Skin rash
  • Infection or pus-filled areas on skin
  • Skin irritation (which was not present before using the medicine)
  • Sudden attacks of sneezing
  • Runny or stuffy nose
  • Wheezing or difficulty breathing

These side effects could be sign of allergic reaction or sensitivity to pyrethrum extract and piperonyl butoxide and should be reported to a doctor as soon as possible.

If you notice any other side effects not listed here, consult a doctor or pharmacist or report them to the FDA.

Dosage

This medicine will be provided with an instruction leaflet; read this through thoroughly before you begin treatment so that you know how to use it correctly.

The amount of medicine you use will depend on the area being treated and the length of your hair. Follow the instructions provided with medicine. If you’re unsure how much to use, consult a pharmacist or your doctor. Never use more of the medicine than is necessary as doing so could increase the risk of irritation and side effects.

Usually at least two treatments of pyrethrum extract and piperonyl butoxide are required to completely remove all lice. The first treatment kills off most of the lice but may not affect unhatched eggs. The second treatment kills of newly hatched lice before they can lay any more eggs. Sometimes a third treatment may be necessary.

How to use liquid, gel or solution pyrethrum extract and piperonyl butoxide

  • Shake the shampoo thoroughly before use. Apply it to dry hair, scalp or skin. The gel or solution should thoroughly dampen the treated area. Wash your hands thoroughly and leave the medicine on the treated area for around 10 minutes, before rinsing it thoroughly with warm water and either soap or shampoo. Then, rinse the area thoroughly and dry with a clean towel.

How to use shampoo pyrethrum extract and piperonyl butoxide

  • Apply the shampoo to dry hair and massage throughout the hair and scalp until the area is completely wet. Wash your hands thoroughly and leave the medicine to work for 10 minutes. Apply a small amount of warm water and lather the shampoo as you usually would to clean the hair. Then, rinse the hair thoroughly and dry with a clean towel.

Treatment for head lice

If you’re using pyrethrum extract and piperonyl butoxide to treat head lice, you should apply the medicine behind the ears and at the back of the neck first before covering the rest of the head. After completing the treatment, you could use a lice comb to remove the dead lice and nits (which are lice eggs). It can be helpful to have someone else complete this step for you to ensure the whole head is combed through properly. Ensure combs are thoroughly washed in very hot water afterwards.

Not suitable for eyelashes or eyebrows

Pyrethrum extract and piperonyl butoxide should not be applied to the eyebrows or eyelashes due to the risk of the medicine coming into contact with the eyes. If you have lice in your eyelashes or eyebrows, consult your doctor. They may be able to recommend a safer treatment.

Interactions

There are no major interactions associated with pyrethrum extract and piperonyl butoxide. However, if you are taking other medicines you should check with a doctor or pharmacist that it is safe to use this lice treatment. Be sure to mention both prescribed drugs and those purchased over the counter, as well as herbal treatments, supplements and multivitamins.

Warnings

Do not swallow, inhale or apply to mucous membranes

Pyrethrum extract and piperonyl butoxide can be extremely harmful if inhaled or swallowed, or if it comes into contact with mucous membranes such as the eyes, inside of the nose, the mouth or the vagina.

If you accidentally swallow or inhale the medicine, contact your local poison control center immediately or, if the victim has collapsed or isn’t breathing, call 911. If it comes into contact with mucous membranes, immediately and thoroughly rinse the area with water and consult a medical professional if irritation occurs.

You can avoid inhaling the medicine by using it in a well-ventilated room. Open windows and doors or turn on a fan while using the medicine.

Skin inflammation

If your skin is severely inflamed, do not use pyrethrum extract and piperonyl butoxide. Doing so could make the condition worse. If in doubt about the severity of skin inflammation, check with a pharmacist or doctor before using this treatment that it is safe to do so.

Allergic reaction

Check the label or package ingredients list carefully before using pyrethrum extract and piperonyl butoxide to check for ingredients that you know you are allergic to. You could ask your pharmacist for advice if there are ingredients you know you need to avoid. If you’ve experienced a reaction to a topical treatment like pyrethrum extract and piperonyl butoxide in the past, you may want to check with your pharmacist or a doctor whether it is safe to use this treatment.

If you notice signs of allergic reaction to pyrethrum extract and piperonyl butoxide, seek medical care urgently. Symptoms of allergy include:

  • Itching, rash or hives
  • Blistering or peeling skin
  • Swelling of the face, lips, tongue or throat
  • Difficulty breathing
  • Chest tightness
  • Hoarseness

Pregnancy and breastfeeding

Pyrethrum extract and piperonyl butoxide is a pregnancy category C drug. This means that there have not been adequate studies in pregnant women, and evidence in animal studies is either inconclusive or suggests a risk to the mother or fetus. For this reason, this medicine should be avoided during pregnancy unless the benefits of the drug far outweigh potential risks.

It isn’t known whether pyrethrum extract and piperonyl butoxide is excreted in human breast milk and, if it is, what risks it could pose to a nursing infant. The medicine should therefore be used with caution in breastfeeding women; it may be safer to avoid breastfeeding while using the treatment.

Avoiding the spread of lice

The main way that lice move from one person to another is close bodily contact. You should avoid close contact with anyone else while you are infected with lice, particularly if you have pubic lice (also known as crabs). If you do come into close contact with someone, make sure they are also treated for lice so that they do not accidentally transfer them back to you after you have been treated.

Lice may be transmitted via clothing, bed sheets or towels so it is incredibly important to sanitize these items immediately after treatment with pyrethrum extract and piperonyl butoxide to avoid spreading them back to yourself or to other people. Clothing, bed sheets and towels should be washed on a very high temperature and then placed in a hot cycle in the dryer. If you cannot wash the items, have them dry cleaned or store them in a sealed plastic bag for at least two weeks.

Be sure to wash hair brushes, combs and other hair tools or accessories in hot water too. Ideally, the water should be above 130 °F and contain soap.

Avoid sharing clothes, sheets, towels or personal care items with other people until the lice have been completely destroyed. You may also be able to prevent the spread of lice by vacuuming rugs, floors and upholstered furniture regularly until the infection has been thoroughly treated. For those who have public lice, clean toilet seats thoroughly and frequently.

Storage

Store pyrethrum extract and piperonyl butoxide in the container it was provided in. Keep it away from heat, moisture and direct light and do not allow it to freeze. The bathroom is not the best place to store this medicine as the heat and humidity could affect it, even if it is the shampoo dosage form that you are using.

Since pyrethrum extract and piperonyl butoxide can be harmful if used incorrectly, it’s very important to keep it away from children and pets. Store it up and away from the ground so that it is not within easy reach. If someone other than yourself wants to use the medicine after you, make sure they check the ingredients and consult a pharmacist or doctor to ensure it is safe for them.

Unused or expired pyrethrum extract and piperonyl butoxide should be disposed of safely according to your healthcare provider’s instructions. Do not pour it down the sink, throw it in the trash or flush it down the toilet as it may come into contact with others. Your healthcare provider or local garbage or recycling center may have a drug take-back program you can use.

Summary

Pyrethrum extract and piperonyl butoxide is a topical treatment for lice. Available in shampoo, gel, liquid and foam dosage forms, it is applied directly to the hair or skin and is absorbed by the lice in order to kill them. It can be purchased over the counter without a prescription, and common brand names in the US include A200, Lice-X, Pyrinex, Rid and Tisit.

There are few side effects associated with this medicine. In rare instances it may cause skin irritation, infection, sneezing, runny nose or breathing difficulties and these should be reported to a doctor immediately. Individuals who have severe irritation of the skin before using pyrethrum extract and piperonyl butoxide may find that the medicine makes it worse and they should therefore avoid it. A doctor or pharmacist may be able to advise whether irritation is severe enough to avoid the treatment.

Two treatments of pyrethrum extract and piperonyl butoxide is usually necessary to completely eradicate lice. The second treatment is usually administered between 7 and 10 days after the first. The medicine should be thoroughly applied to dry hair and skin and left to work for 10 minutes, before being rinsed with warm water and either soap or shampoo.

Avoid transmitting lice to others by avoiding close contact and thoroughly washing clothes and personal care items. Wash towels, bed sheets and clothes in hot water, then dry in a hot dryer cycle. Hairbrushes, combs and other hair accessories should also be thoroughly washed in hot, soapy water. If you have pubic lice, ensure your partner is treated too so that they do not pass the lice back to you at a later point.

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Last Reviewed:
January 30, 2018
Last Updated:
January 27, 2018
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