Factors Affecting Topical Drug Absorption Through Skin
📌 Absorption is increased by drugs with more oil content (lipophilicity).
💧 Drug absorption is enhanced when the top layer of the epidermis is moist, often aided by occlusive dressings.
⏳ Longer contact time between the drug and the skin leads to greater drug absorption.
🩹 Drugs applied to skin surfaces with abrasions or breaches in the epidermis are absorbed more easily.

Specific Topical Dosage Forms and Applications
👁️ Topical preparations for the eye typically target the anterior segment (cornea, conjunctiva, etc.); bioavailability is influenced by the tear film and cornea.
💨 Inhalation dosage forms are administered via nasal or oral airways, requiring very small drug particles to effectively reach the target organs, primarily the lungs and bronchi.
🧴 Vaginal dosage forms commonly include tablets, suppositories, gels, or creams; semi-solid forms (gels/creams) last longer than solutions.
⏳ Vaginal tablets offer a long drug release time (up to several hours) by adhering to the vaginal mucosa until dissolved.

Suppositories and Transdermal Preparations
💊 Suppositories are solid dosage forms molded into the rectal shape for local or systemic effects; the base melts or dissolves upon application to release the active substance.
🔄 Transdermal preparations are designed to facilitate the passage of the active drug substance through the skin into the systemic circulation to achieve a systemic event.

Key Points & Insights
➡️ Amphipathic drugs (containing both hydrophilic and lipophilic properties) are generally more easily absorbed across biological barriers like the skin or cornea.
➡️ Vaginal tablets are preferred over solutions for prolonged action due to their ability to adhere and slowly dissolve over several hours.
➡️ The efficacy of inhalation drugs is directly dependent on the particle size of the drug, which must be very small to reach the lower respiratory tract.

📸 Video summarized with SummaryTube.com on Nov 17, 2025, 14:05 UTC