Dermatological Products Quiz

Semisolid Dosage Forms and Transdermal Systems

• Semisolid dosage forms, used topically, treat skin conditions. Examples include ointments, creams, gels, pastes, and plasters.
• Other dosage forms include solutions, powders, and transdermal drug delivery systems. Oral therapy can also be used for skin conditions.
• Semisolid dosage forms can be applied to the skin, eyes, or used nasally, vaginally, or rectally.
• Semisolid forms can be medicated (for therapeutic effects) or unmedicated (for physical effects like protection or lubrication).
• Topical preparations (medicated) are used for both local and systemic effects.
• A topical dermatological product delivers medication into the skin to treat dermal disorders; the skin is the target organ.
• A transdermal product delivers drugs through the skin (percutaneous absorption) to the bloodstream for systemic effects, not targeting the skin as the organ.
• Systemic drug effects should be considered when using topical preparations if the patient is pregnant or is nursing.
• In treating skin diseases, the medication should penetrate and be retained in the skin for some time.
• Drug penetration depends on the substance's physiochemical properties, the pharmaceutical vehicle, and the skin's condition.
• Normal skin is a barrier to penetration by external agents and to water loss.
• The skin is histologically divided into epidermis (corneum is the outer layer, living epidermis exists underneath), dermis, and subcutaneous layers.
• Sebaceous glands, sweat glands, and hair follicles originate in the dermis and subcutaneous layers and raise to the skin surface.
• The stratum corneum is a desquamating horny layer, 10-15 µm thick, made up of flat, partially desiccated dead epidermal cells. It contains 40% protein (keratin) and 40% water and the remaining lipid as triglycerides, free fatty acids, cholesterol, and phospholipids.
• The skin surface has a film of emulsified material (sebum, sweat, and desquamating epidermal cells). This film varies in composition, thickness, and continuity and offers little resistance to drug penetration.
• Hair follicles and gland ducts provide drug molecule entry, but their small relative area is a minor factor in absorption.
• The stratum corneum acts as a semipermeable artificial membrane. Drug molecules penetrate by passive diffusion.
• The rate of drug movement across the skin depends on the drug concentration in the vehicle, aqueous solubility of the drug, and the oil-water partition coefficient between the stratum corneum and the vehicle.
• Drug molecules can pass through deeper epidermal tissue, into the dermis, and if the vascularized dermal layer is reached, they are available for systemic absorption.
• Ointments are semisolid preparations applied externally to skin or mucous membranes. These are often medicated or unmedicated (protectants, emollients, lubricants).
• Ointment bases can have oleaginous, absorption, water-removable, or water-soluble properties.

Ointment Bases

• Oleaginous (hydrocarbon) bases provide emollient effects, protection against moisture loss, and occlusion. These bases are difficult to wash off. Examples include petrolatum, white petrolatum, white ointment, and yellow ointment.
• Petrolatum is an unctuous mass that varies in color from yellowish to light amber. It's a purified mixture of semisolid hydrocarbons from petroleum. It melts at 38–60°C.
• White petrolatum is a refined mixture of petrolatum with no color.
• Yellow ointment is a mixture of 50 g yellow wax and 950 g of petrolatum.
• Absorption bases allow the incorporation of aqueous solutions, resulting in water-in-oil emulsions. Examples include hydrophilic petrolatum, which is based on water-in-oil emulsions that permit the incorporation of additional aqueous solutions, such as lanolin.
• Water-removable bases are oil-in-water emulsions that easily wash off. Hydrophilic ointment is an example.
• Water-soluble bases don't contain oleaginous components, are water-soluble, and are easily removed. An example is Polyethylene Glycol Ointment.
• Polyethylene glycol is a polymer derived from ethylene oxide and water. Its molecular weight determines its form.

Preparation of Semisolid Formulations

• Ointments are prepared by incorporation or fusion.
• Incorporation: Mixing components until uniform. This might include using a mortar and pestle, spatula on a slab, or other tools
• Fusion: Melting components to make a uniform mixture that is cooled to a firm state afterward. Heat-sensitive components should be added last.

Packaging Semisolid Preparations

• Ointments and other semisolid preparations are packaged in large-mouth ointment jars or metal/plastic tubes and stored in well-closed containers in cool places.
• Light-sensitive preparations are packaged in opaque or light-resistant containers for protection.
• Additional standards include viscosity testing and in vitro drug release testing (to ensure uniformity).

Percutaneous Absorption:

• Drug absorption through skin primarily occurs through passive diffusion. Drugs must dissolve within a vehicle, diffuse through the vehicle to the skin surface, then penetrate skin layers to be absorbed. Drugs and nutrients also use membrane transporters (specialized proteins and cell surface receptors; this transport is sometimes energy dependent (active transport) or energy-independent (passive transport))
• Routes of absorption include transepidermal (intercellular and intracellular/transcellular—polar, low MW), and transappendageal (hair/sweat) —polar, very high MW).
• Percutaneous absorption models can be performed in vivo (in humans, animal models), or in vitro using diffusion chambers with skin samples. Studies may determine skin bioavailability, or drug level in the blood. Excised animal skin can vary in permeation in comparison to human skin.

Factors Affecting Percutaneous Absorption

• Properties of the drug (MW, solubility in lipids/water, partition coefficient, pKa).
• Characteristics of the carrier vehicle.
• Skin condition (normal vs. abraded/cut).

Creams

• Creams are semisolid preparations, usually oil-in-water emulsions with water and stearic acid or other oleaginous components. Water evaporates after application, leaving a residue film.

Gels

• Gels are semisolid dispersions of molecules in an aqueous vehicle, due to a gelling agent. Synthetic macromolecules (carbomer 934, cellulose derivatives like CMC or HPMC) and natural gums (tragacanth) are used. Gels can thicken on standing, needing to be shaken to liquefy. They may contain drugs/solvents, preservatives, and stabilizers.

Transdermal Preparations

• Topical ointments, creams, and gels can deliver drugs systemically; ideal drug migration is through the skin and into underlying blood supply, without buildup.
• Penetration enhancers (like DMSO, ethanol, PG, glycerin, PEG, urea) aid in this systemic transfer.

Ophthalmic Ointments and Gels

• Ointments/gels used for eye treatment should not irritate the eye and permit drug diffusion.
• Bases often include petrolatum and liquid petrolatum mixtures.
• Some water-miscible ingredients like lanolin might be added to an ointment.

Miscellaneous Semisolid Preparations

• Pastes are stiffer semisolid preparations, containing higher solid loads (often 25%).
• Plasters are solid or semisolid adhesive materials applied to the skin.
• Glycerogelatins are plastic masses containing gelatin, glycerin, water, and a medicinal substance. They are applied for prolonged contact

Other Notes

• Compendial requirements for ointments, like microbial content, minimum fill, packaging, storage, and labeling, must be met.
• In vitro drug release testing is a significant element of analysis.
• The selection of the appropriate base is crucial, depending on factors such as desired release rate, drug absorption, and occlusion of moisture.

Test your knowledge about dermatological products and their applications. This quiz covers essential aspects of transdermal drug delivery, patient preparation, and product effectiveness. Perfect for pharmacy students and healthcare professionals.