Products
Scabi-med cream containing 5% permethrin was approved in many countries in 2018. For the years prior to that, no finished drug product was registered for the treatment of scabies in many countries following the cessation of sales of Eurax (crotamiton). In other countries, however, the cream had been available for years or even decades. InfectoScab in Germany, for example.
Structure and properties
Permethrin (C21H20Cl2O3, Mr = 391.3 g/mol) belongs to the pyrethroids. These are synthetically produced derivatives of pyrethrins naturally occurring in certain composite flowers. Permethrin exists as a yellow to slightly orange-brown, lipophilic, viscous liquid or as a hardening mass and is poorly soluble in water. Two carbon atoms on the cyclopropane ring are chrial. Permethrin is a mixture of 4 stereoisomers, each consisting of two and two isomers. Drugs typically contain 25% of the -isomers and 75% of the -isomers.
Effects
Permethrin (ATC P03AC04) has acaricidal properties, meaning it is effective against arachnids such as mites and ticks. Furthermore, it also has insecticidal and insect repellent effects and is also effective against lice and fleas, among others. The drug target is voltage-gated sodium channels in the cell membranes of neurons. The binding leads to excitation states, coordination disorders and paralysis in the mites. Due to structural differences, permethrin does not interact with human sodium channels. The small amount that does enter the circulation is rapidly biotransformed. The inactive metabolites are excreted mainly in the urine.
Indications
For the treatment of scabies (scabies) in adults and children after 2 months of age.
Dosage
According to the expert information and the package leaflet. Usually, a single application is sufficient. If the infestation persists or recurs, therapy can be repeated after two weeks. The amount applied depends on the age of the patient. The cream is applied carefully and in a thin layer on dry skin. The whole body must be covered with cream, except for the face and head (adults) or the area around the mouth and eyes (children, older adults over 65 years). The cream must be left to act for at least 8 hours, for example overnight. Patients should shower only 8 to 12 hours after application of the cream to remove any residues. After the therapy, the so-called post-scabial eczema may persist for up to one month. It should be treated with skin care products. Oil baths are also recommended. Close contacts such as partners or family members may also be affected and should be examined.
Contraindications
The cream is contraindicated in cases of hypersensitivity to the active ingredient, excipients, or other pyrethroids. For complete precautions, see the drug label.
Interactions
No data on drug-drug interactions are available. Treatment with topical glucocorticoids should be given only after therapy with permethrin to avoid suppressing the immune response.
Adverse effects
The most common possible adverse effects include paresthesias, a burning sensation on the skin, stinging, pruritus, an erythematous rash, and dry skin. However, these side effects may also be due to the disease.
