Kruidvat (Permethrin)

• Permethrin is a pyrethroid insecticide applied topically to treat common ectoparasitic skin conditions caused by mites and lice.
• Scabies: eliminates Sarcoptes scabiei mites, relieving itching and halting spread.
• Pediculosis (lice infestation): kills head lice and nits, terminating the infestation and preventing re‑infestation.
• Crusted scabies: controls severe mite burden in immunocompromised patients, reducing disease severity.
• Contact prophylaxis: applied to household members to prevent spread of scabies or lice.
• Scabies in children: safe for use in children over 2 months, providing effective mite eradication.

• Permethrin acts by binding to voltage‑gated sodium channels on the neuronal membranes of arthropods. This binding prolongs the opening of the channels, leading to repetitive nerve firing, loss of motor control, paralysis, and ultimately death of the parasite. Human skin cells are relatively insensitive, allowing topical use with limited systemic absorption. The effect is rapid, and the compound remains active on the skin for several hours, ensuring complete eradication of the target organisms.

Topical permethrin may cause local skin reactions and, rarely, systemic adverse events.

Common Side Effects

• Skin irritation: mild redness, itching, or burning at the application site.
• Pruritus: transient itching unrelated to infestation.
• Dryness: mild skin dryness or flaking.

Serious or Rare Side Effects

• Allergic contact dermatitis: severe rash, swelling, or blistering.
• Stevens‑Johnson syndrome: extremely rare severe skin reaction.
• Anaphylaxis: life‑threatening allergic response.

When using permethrin topical products, certain precautions help ensure safety and effectiveness.

• Avoid application on broken or inflamed skin: may increase irritation.
• Do not use on infants under 2 months: safety not established.
• Keep away from eyes, mouth, and mucous membranes: avoid accidental ingestion.
• Wash hands thoroughly after application: prevent transfer to others.
• Do not cover treated area with occlusive dressings: may enhance absorption.
• Store at room temperature below 25°C: keep in original packaging, protect from moisture and direct sunlight.

Permethrin applied to the skin has a low potential for drug interactions, but certain co‑applications should be considered.

Major Interactions (Avoid)

• Concurrent use with other neurotoxic insecticides (e.g., organophosphates): may increase skin irritation risk.
• Application with strong keratolytic agents (e.g., salicylic acid): can enhance systemic absorption.

Moderate Interactions (Monitor Closely)

• Co‑application with sunscreen or moisturizers: may reduce permethrin efficacy.
• Use with other topical antiparasitics: monitor for additive skin reactions.
• Systemic medications that lower seizure threshold: rare concern if significant absorption occurs.