Pyrethrins are natural insecticides derived from the dried flowers of certain species of chrysanthemums, particularly Chrysanthemum cinerariifolium and Chrysanthemum coccineum. These insecticides have been used for centuries to control a wide range of insect pests.

Pyrethrins are a group of compounds that have been derived from flowers. Topical pyrethrins are used for the treatment of lice infestations in humans. The spray may be used as an insect repellant.

Pyrethrins Uses:

• Pediculus humanus infestations:
  • Pediculus humanus infestations are advised for treatment with it (head lice, body lice, pubic lice, and their eggs)

Pyrethrins Dose in Adults

Pyrethrins Dose in the treatment of Pediculus humanus infestations:

• Apply the pyrethrin solution to dry hair (for head lice) or the affected area (for pubic lice).
• Leave it on for 10 minutes.
• Wash and rinse the hair or affected area thoroughly after the 10 minutes are up.
• Repeat this treatment again after 7 to 10 days.

This process helps kill the lice and their eggs and is typically done twice to ensure all the lice are eliminated.

Dose in Children:

Refer to adults dosing.   

Pregnancy Risk Category: B

• Pregnant women can be treated with a combination of pyrethrins and piperonyl butoxide to address lice infestations, as recommended by the Centers for Disease Control and Prevention (CDC).
• This treatment is considered safe for pregnant women when used according to the recommended guidelines.

Use during breastfeeding:

• According to the Centers for Disease Control and Prevention (CDC) guidelines, breastfeeding women can use a combination of pyrethrins and piperonyl butoxide to treat lice infestations.
• This treatment is considered safe for breastfeeding mothers when used as directed.

Dose in Kidney disease:

• If the manufacturer's labeling does not provide specific dosage adjustments for individuals with renal impairment, it is important to follow the standard recommended dosing instructions.

Dose in Liver disease:

• If the manufacturer's labeling does not provide specific dosage adjustments for individuals with hepatic (liver) impairment, it is important to adhere to the standard recommended dosing instructions.

Side effects of Pyrethrins:

• Central nervous system:
  • Localized burning
• Dermatologic:
  • Skin Irritation (With Repeat Use)
  • Burning Sensation Of Skin
  • Pruritus
  • Stinging Of The Skin

Contraindications to Pyrethrins:

Hypersensitivity (allergic reaction) to pyrethrins, piperonyl butoxide, or any ingredient in the product is a contraindication, which means that individuals who are known to be allergic to these substances should not use products containing them. Allergic reactions can range from mild skin irritation to more severe symptoms, and using such products can exacerbate these allergic responses.

Additionally, over-the-counter (OTC) labeling typically provides specific instructions for safe use. In the case of products containing pyrethrins and piperonyl butoxide:

• Do not apply the product near the eyes.
• Avoid using it inside the nose, mouth, or vagina.
• Refrain from using the product on infestations in the eyebrows or eyelashes.

These instructions are important to prevent potential adverse reactions or irritation in sensitive areas of the body.

Warnings and precautions

Topical irritation

• Topical irritation, such as scalp itching and redness, can sometimes occur as a side effect when using products like those containing pyrethrins and piperonyl butoxide for lice treatment. This irritation is usually mild and temporary.

Monitoring Parameters:

None mentioned. Monitor for clearance of the affected area.   

How to administer Pyrethrins?

• External Use Only: This product is meant to be used on the outside of your body, on your hair and skin. Do not swallow it or put it in your eyes, mouth, or other sensitive areas.
• Apply Thoroughly to Wet the Area: Put enough of the solution to make sure the entire infested area, including your hair, gets completely wet. Your hair should be dry when you put the product on.
• For Head Lice: Start by applying the solution behind your ears and at the back of your neck, where lice like to hide.
• Leave it on for 10 Minutes: Allow the solution to stay on the area for exactly 10 minutes, but no longer.
• Wash Off with Warm Water and Soap: After the 10 minutes, wash the area thoroughly with warm water and soap or shampoo. Make sure to clean it well.
• Use a Comb: For head lice, you can use a fine-toothed comb or a special lice/nit comb to remove lice and their eggs from your hair. Comb carefully.
• Remove Remaining Eggs by Hand: If there are any eggs left (nits), you can use a disposable glove to pick them out by hand.
• Protect Your Eyes: When rinsing your hair, be extra careful not to get the product in your eyes. You can cover your eyes with a washcloth or towel to keep them safe.

Mechanism of action of Pyrethrins:

Pyrethrins from Chrysanthemum Flowers:

• Pyrethrins are insecticides that come from certain types of chrysanthemum flowers.
• These natural compounds are used to kill insects, including lice.

Similar to DDT Mechanism:

• The way pyrethrins work on lice is similar to how the chemical DDT works.
• They affect the neuronal (nerve cell) membranes of lice.

Piperonyl Butoxide Boosts Effectiveness:

• Piperonyl butoxide is often added to pyrethrins in insecticide products.
• It helps make pyrethrins more effective against insects by slowing down their metabolism, especially in arthropods (like lice).

By combining pyrethrins from chrysanthemum flowers with piperonyl butoxide, the insecticide becomes more potent in dealing with lice and other pests.

International Brand Names of Pyrethrins:

• A-200 Lice Treatment Kit
• A-200 Maximum Strength
• LiceMD Complete
• LiceMD Treatment
• RID Lice Killing
• Licide
• RID Lice Elimination Essentials
• Pronto Plus Complete Lice Removal System
• RID Lice Treatment Complete
• R & C Shampoo/Conditioner
• RID Mousse
• Pronto Lice Control
• R & C II
• Banlice Mousse
• Kicesol
• Kwell-P
• Lice-Enz
• Licesol
• Milice
• Spray-Pax

Pyrethrins Brand Names in Pakistan:

Not Available.