What are the characteristics of dermal administration?

Update Date: Source: Network

The characteristics of topical administration include avoiding inactivation of drugs in the gastrointestinal tract and the first-pass effect of the liver; maintaining stable blood drug concentrations and keeping them within the effective concentration range for a longer time; reducing the irritation of drugs on the gastrointestinal tract; and improving safety, allowing patients to stop taking the medication at any time.

1. What is topical administration?

Topical administration mainly involves the use of pour-on formulations, which must meet two conditions: first, the drug must be dissolved from the formulation matrix and then penetrate through the stratum corneum and epithelial cells; second, the drug must be lipid-soluble due to passive diffusion absorption. Currently, the best bioavailability of pour-on formulations is 10%-20%.

2. Attention should be paid to selecting different drug dosage forms according to different skin lesions.

For example, when acute inflammatory skin lesions only have erythema, papules, and vesicles, powders or lotions can be selected; when there is erosion and excessive exudation, wet compresses with solutions should be used. For subacute inflammatory skin lesions with a small amount of exudation, emulsions, pastes, or oils can be selected. For chronic inflammatory skin lesions, ointments, emulsions, plasters, films, and tinctures can be chosen. For patients with non-lesional itching only, emulsions or tinctures can be used. For skin lesions with breakage, excessive exudation, or complicated infections, solution formulations can be selected, and wet therapy or semi-exposure treatment can be applied.

3. Medication techniques

Before applying medication, scabs, scales, etc. on the skin lesions should be removed. If the condition permits, they can be removed by showering or soaking. If necessary, the patient's hair can be trimmed. Aerosols, lotions, and other suspensions should be thoroughly shaken before use; lotions and pastes should not be used on hairy areas; ointments and plasters are contraindicated for acute dermatitis with excessive exudation; tinctures should not be used when there is erosion or exudation; patients with skin chapping, acute inflammation, or exudative erosion should also avoid using tinctures.