transdermální

Transdermální is a Czech term meaning transdermal. In pharmacology it refers to the delivery of medication through the skin. The method is also known as transdermal drug delivery in English. Drugs taken transdermally are applied directly to the skin in the form of patches, creams, ointments, or gels. The skin acts as a selective barrier; a small amount of drug penetrates through the epidermis and dermis before reaching the bloodstream. Because the absorption is controlled, drugs can be released at a steady rate over a prolonged period.

The most common clinical uses are for hormone replacement therapy, treatment of angina pectoris, glaucoma, smoking cessation, and the relief of arthritis pain. Other uses include muscle relaxants, anti-inflammatory agents, and controlled pain management. Transdermal esterpropryl, patch, and other medicated gels are particularly useful for drugs that suffer from extensive first‑pass metabolism or a short half‑life if taken orally. By bypassing the gastrointestinal tract and liver, transdermal administration can improve bioavailability and reduce systemic side effects.

There are limitations to the method. Effective delivery requires a drug molecule with optimal lipophilicity and molecular weight. Drugs larger than 500 daltons or with poor permeability may be unsuitable. Skin irritation, dermatitis, or allergic reactions can occur, especially with adhesives in patches. Cost can be higher than oral forms. Regulatory approval processes require demonstration of safety, efficacy, and controlled release.

Design of transdermal patches uses a drug reservoir, rate‑control membrane, and adhesive backing to maintain contact with the skin. Various enhancers such as ethanol or lipid agents are sometimes added to increase permeability. Over the past few decades, transdermal technology has expanded from simple dosage forms to sophisticated systems incorporating micro‑pumps, microneedles, and hydrogel carriers. The approach remains important in modern drug delivery because of its convenience and patient compliance.