Topical Dosage Forms and Transdermal Drug Delivery

Specific Learning Outcomes

• Students will be able to describe various topical dosage forms.
• Students will be able to describe transdermal drug delivery systems.
• Students will be able to describe advantages and disadvantages of topical dosage forms.
• Students will be able to identify auxiliary label requirements for topical dosage forms.

Pluronic Lecithin Organogel (PLO)

• PLO is used as a base for transdermal drug administration.
• It is a popular base for manufactured and compounded topical medications intended for systemic effects.

Absorption Bases

• Ointment bases that absorb water
• Two types: anhydrous and water-in-oil (w/o) emulsions

Anhydrous Absorption Bases

• Allow incorporation of aqueous solutions to create a water-in-oil emulsion, but do not contain the original aqueous solution.

Anti-Inflammatory

• Reduce skin inflammation (e.g., hydrocortisone)

Anti-Pruritic

• Reduce skin itchiness (e.g., calamine)

Astringents

• Topical drugs to shrink and toughen tissue (e.g., zinc sulfate)

Collodions

• Syrupy topical emulsion that dissolves into alcohol and ether.
• After application, these solvents evaporate, leaving a medicated film coating on the skin.

Epicutaneous Form of Administration

• Topical use of a drug for a local effect.

Inunction

• Gently rubbing a cream or ointment into the skin to increase absorption.

Liniments

• Solutions or mixtures applied to the skin via massage.

Lotions

• O/W emulsions that are quick and easy to apply to large areas.

Ointments

• Semi-solid emulsions for topical use on the skin.
• Categorized by the USP: oleaginous, absorption bases, water-removable, and water-soluble bases.

Oleaginous Bases

• Also called hydrocarbon bases.
• Made from petrolatum.
• Can only accept small amounts of water or hydrophilic components.
• Greasy and hard to wash off.

Pastes

• Mixtures with high concentrations of absorbed powders.
• Stiff and do not soften.

Plasters

• Drug ingredients added to a material that sticks to the skin (like a band-aid).

Shampoos

• Products used to treat scalp conditions.

Soaps

• Cleansing solid bars worked into lather for washing the skin.

Sticks

• Convenient dosage form for administering topical medications.

Sun Protection Factor (SPF)

• A relative scale to gauge exposure time before skin reddens.
• SPF 15 provides 15 times longer protection than without sunscreen.

Tinctures

• Alcoholic or hydroalcoholic solutions from plant extractions.
• Often painted on the skin.

Topical Aerosols

• Sprays containing anti-infectives or anesthetics for injured skin.

Topical Anaesthetics

• Cause numbness to the skin (e.g., solarcaine).

Topical Powders

• May be non-medicated and contain moisture-absorbing substances to keep skin dry.
• Used to treat athlete's foot.

Topical Route of Administration

• Administration of a drug to the skin or mucous membrane.
• Also referred to as epicutaneous route (local effect) or transdermal route (systemic effect).

Transdermal Form of Administration

• Formulations designed for continuous drug supply into the bloodstream via skin absorption.
• Includes ointments, gels, lotions, patches, and disks.

Water-Soluble Bases

• Contain only water-soluble compounds.
• Also called greaseless.
• Includes gels and jellies (single-phase systems) or magmas and milks (two-phase systems).

Topical Preparations: Common Skin Conditions

• Acne, allergic reactions, bacterial infections, burns, corns/calluses, diaper rash, eczema, fungal infections, psoriasis, rosacea, skin infestations (lice, scabies), ulcers, pressure sores, viral infections (warts, cold sores), and wrinkles.

Drug Absorption - Topical Preparations

• Drugs must be in contact with and stay within the skin to treat skin conditions.
• Some topical preparations may have systemic effects.

Absorption Factors

• Drug properties
• Skin condition (age, hydration, cuts)
• Thickness of the stratum corneum
• Application area
• Contact time
• Vehicle
• Chemicals added

Ointments

• Semi-solid preparations for skin application.
• Historically used animal fats/oils, now mostly synthetic or petroleum-based.
• Categorized by the USP: oleaginous, absorption, water-removable, water-soluble.

Oleaginous Bases (Hydrocarbon Bases)

• Prepared from petrolatum.
• Can only accept tiny amounts of water.
• Greasy, hard to wash off.
• Advantages: protective barrier, emollient, occlusive and stable.
• Disadvantages: greasy, sticky, difficult to wash, occlusive prevents drainage, difficulty incorporating aqueous components.

Absorption Bases (Ointments)

• Ability to absorb water, but not necessarily used for water absorption.
• Two types: anhydrous and oil-in-water (o/w) emulsions.
• Anhydrous: permit water incorporation to form an O/W emulsion, but do not contain the aqueous part.

Water-Removable (Water-Washable) Bases (Creams)

• Oil-in-water (O/W) mixtures.
• Easily removed with water.
• Non-greasy, easier for patients.

Water-Soluble Bases (Gels, Jellies, Magmas)

• Contain only water-soluble compounds.
• Also called greaseless.
• Include single-phase gels/jellies and two-phase magmas/milks.

Selection of Ointment Bases

• Occlusive (hydrocarbon) bases used for dry skin lesions.
• Water-washable or water-soluble bases for moist skin conditions.
• Factors to consider when selecting include drug stability, release, absorption, washability and patient convenience.

PLO Gel

• Used as a base for transdermal drug delivery.
• Popular for manufactured and compounded topical medications for systemic effects.
• Consists of an oil phase and water phase.

Packaging and Storage of Topical Medications

• Packaging is product-specific.
• USP guidelines used for compounded products.
• Certain topical medications need refrigeration or mixing prior to dispensing.

Application Process of Topical Dosage Forms

• Wash affected areas according to directions.
• Remove required amount of product without contaminating.
• Apply to affected area.
• Avoid covering treated areas with dressings.
• Monitor for allergic reactions or side effects.
• Important to discontinue if reaction occurs.

Other Topical Dosage Forms

• Collodions, liniments, lotions, pastes, plasters, shampoos, soaps, topical aerosols, topical powders, solutions and tinctures, sticks (e.g. lip balm).

Transdermal Drug Delivery Systems (TDDS)

• Systems designed for drug passage through the skin into the circulatory system for systemic effects.
• Drug is contained in patches and absorbed percutaneously.
• Advantages: eliminate oral route challenges, convenient, easily stopped, good for extended use.
• Disadvantages: not all drugs are suitable, some patients can develop contact dermatitis.

This quiz covers various topical dosage forms, including transdermal drug delivery systems. Students will learn about the advantages and disadvantages of these forms, as well as the auxiliary label requirements. Knowledge of absorption bases and specific topical agents like anti-inflammatory and astringent medications will also be tested.