Various Type of Topical Dosage Form

Topical dosage forms are drug preparations applied to the skin or mucous membranes. They are categorized into three main physical forms: solid (powder), semi-solid (ointment, cream, gel, paste), and liquid (solution, tincture, lotion).

Powders are solid preparations of dry, active, and inactive substances with small molecular sizes to prevent skin irritation. They are easily applied to large or folded skin areas (neck, belly, armpit, groin) and are suitable for patients with excessive sweating. Powders act as absorbents, antiseptics, antipruritics, and antiperspirants.

Ointments are homogeneous, semi-solid preparations applied to skin or mucous membranes, containing less than 20% water dispersed in oil, making them oily. They serve as carriers for active ingredients, offering protective and moisturizing effects. Ointments are occlusive, difficult to wash off, and preferred for dry skin.

Creams are semi-solid dosage forms containing active substances dissolved in a water-in-oil or oil-in-water emulsion. Modern creams are typically oil-in-water emulsions, making them easier to wash off and more cosmetically acceptable than ointments. They are less greasy, easier to apply, and suitable for covering parts of the skin.

Gels are clear, semi-solid dosage forms with small or large molecules in a liquid vehicle, resembling jelly. They are available in hydrophobic (oil-based) and hydrophilic (water-based) forms. Gels are non-greasy, adhere well, form a protective layer, are washable, spread easily, and provide a cooling effect.

Pastes are semi-solid preparations containing high concentrations (over 50%) of undissolved powder. They are less oily, thicker, and stiffer than ointments, allowing them to absorb serous secretions. Pastes are not suitable for hairy areas.

Liquid preparations include solutions (water-based, clear, homogeneous), tinctures (alcohol-based, causing stinging on abraded skin), and lotions (oil-and-water mixtures with a high water percentage). Lotions spread easily, absorb quickly, feel light, and are ideal for dry skin diseases, hairy areas, minor excoriations, ulcers, and oozing lesions, providing a cooling effect.

Eye preparations must be sterile, non-irritating, and either semi-solid or liquid, applied to the conjunctiva, conjunctival sac, or eyelids. Common types are ophthalmic drops (liquid/oily solutions/suspensions/emulsions with small particle size, sterile, isotonic) and eye ointments (sterile, clear, particle-free, with a melting point near body temperature). Eye drops offer high local concentration and lower systemic adverse effects, while ointments provide longer drug exposure. Ointments can cause temporary blurred vision and are best used overnight.

Otic topical drugs are administered directly into the ear canal, providing high local drug concentrations, rapid delivery, good patient compliance, and the ability to combine different drugs. The main limitation is potential ototoxicity if drug concentrations are too high.

Sprays are solutions of water or oil in coarse droplets or fine solid forms, applied topically (nasal, throat, skin). Inhalations are administered through nasal or oral airways for systemic or local effects, coming in powders, gases, aerosols, solutions, and suspensions. Aerosol inhalations are used for respiratory conditions like asthma. Particles less than 6 microns reach bronchioles, and less than 2 microns reach alveoli. MDIs (metered-dose inhalers) are used for potent substances. Inhalations act rapidly with no first-pass metabolism but can be difficult to handle and lead to overdose.

Vaginal dosage forms include tablets, suppositories, gels, creams, and solutions, inserted for local (antiseptic, antibacterial, antifungal, contraceptive) or systemic effects. Suppositories for vagina (ovules) dissolve quickly. Rectal suppositories are solid dosage forms molded to the rectum for local (constipation, hemorrhoids) or systemic effects.

Transdermal preparations deliver active substances through the skin into systemic circulation for systemic effects. Advantages include avoiding first-pass metabolism, patient comfort (non-invasive), and long-lasting effects. However, only a few medicinal substances can be formulated transdermally due to requirements for both water and fat solubility. Some patients may also develop contact dermatitis.