Semi-solid topical products 7

Page 1: Introduction to the Lecture

  • Title: PHAR 202 Towards unbounded thinking. Semi-solid Topical Products 2

  • Presenter: Carol Yousry, Ph.D.

  • Affiliation: NGU, SCHOOL of PHARMACY, Oct-24

Page 2: Learning Objectives

  • Objectives:

    • Describe the structure and function of the skin.

    • Detail the mechanisms for drug transport to and across the skin.

    • Explain the mathematics associated with drug flux through the skin.

    • Identify strategies for manipulating drug movement across the skin.

    • Connect formulation characteristics to their functionality in topical products.

Page 3: Learning Outcomes

  • Outcomes:

    • Integrate fundamental science knowledge to explain drug delivery through biological barriers.

    • Utilize knowledge of semisolid dosage forms and topical preparations to address therapeutic issues concerning dosing and administration routes.

Page 4: Formulations for Application to the Skin

  • Ointments:

    • Fatty preparations that hydrate skin by preventing moisture loss.

    • Often used for dry, scaly lesions.

    • Unmedicated Ointments: Serve as emollients to soothe and hydrate.

    • Types of Bases:

      • Hydrocarbon base

      • Absorption base

      • Emulsifying base

      • Water-soluble base

Page 5: Hydrocarbon Bases

  • Composition:

    • Made from soft, hard, or liquid paraffins.

    • Silicones (e.g., Dimethicone) may enhance skin smoothness.

  • Advantages:

    • Compatible with most drugs.

    • Provide emollient effects and moisture retention.

    • Effective occlusive dressings that stay on the skin for extended periods.

    • Difficult to wash off due to water immiscibility.

Page 6: Hydrocarbon Bases - Disadvantages

  • Limitations:

    • Only suitable for dry skin; not for weeping wounds.

    • Thick, greasy consistency can be hard to spread and messy.

    • May incorporate powdered substances (up to ~15% w/w) using liquid petrolatum as a levigating agent.

    • Examples: Petrolatum, white petrolatum, yellow ointment, white ointment.

Page 7: Absorption Bases

  • Definition:

    • Hydrocarbon base with a miscible polar substance serving as an emulsifier (e.g., lanolin).

  • Advantages:

    • Absorb water (up to 15%).

    • Provide occlusion and hydration benefits.

    • Less greasy compared to hydrocarbon bases.

    • Suitable for weeping skin.

    • Examples: Wool Alcohols BP, Simple Ointment BP.

Page 8: Emulsifying Bases

  • Function:

    • Similar to absorption bases but form oil-in-water (o/w) emulsions.

  • Advantages:

    • Easily washed off and less greasy.

    • Effective for skin contact without staining.

    • Suitable for weeping skin.

Page 9: Emulsifying Bases - Components

  • Common Emulsifiers:

    • Sodium lauryl sulfate, cetrimide, cetomacrogol used with cetostearyl alcohol.

  • Examples:

    • Emulsifying Wax BP (10% w/w sodium lauryl sulfate + 90% w/w cetostearyl alcohol),

    • Cetrimide Emulsifying Wax BP (cationic),

    • Cetomacrogol Emulsifying Wax BP (non-ionic).

Page 10: Emulsifying Bases - Formulations

  • Examples of Emulsifying Ointments:

    • Emulsifying Ointment BP (30% Emulsifying Wax, 50% White Soft Paraffin BP, 20% Liquid Paraffin BP) - anionic.

    • Cetrimide Emulsifying Ointment BP (same base proportions) - cationic.

    • Cetomacrogol Emulsifying Ointment BP - non-ionic (similar proportions).

Page 11: Emulsifying Ointments - Formulations Continued

  • Reiteration of Examples:

    • Emulsifying Ointment BP - anionic,

    • Cetrimide Emulsifying Ointment - cationic,

    • Cetomacrogol Emulsifying Ointment - non-ionic.

Page 12: Water Soluble Bases

  • Definition:

    • Made from water-soluble polyethylene glycols.

  • Advantages:

    • Greaseless, spreads easily, mixes well with skin secretions, easy to wash off.

  • Disadvantages:

    • Lose semi-solid form if >10% water is added.

    • Incompatibility with certain drugs (e.g., phenols, penicillin).

Page 13: Preparation of Ointments by Incorporation

  • Methods:

    • Components mixed using mortar and pestle or spatula on an ointment slab.

    • Aim for a uniform preparation.

    • Avoid using metal spatulas with reactive components (e.g., iodine).

Page 14: Incorporation of Solids

  • Process:

    • Geometric dilution ensures uniform blending.

    • Reducing powder particle size beforehand may reduce grittiness.

    • Use levigation to create a smooth dispersion.

Page 15: Fusion Method for Ointments

  • Definition:

    • Used for ointments with components like beeswax that do not mix easily by incorporation.

  • Process:

    • Melt components together and cool with stirring.

    • Incorporate unmelted components during cooling.

Page 16: Creams as Formulations

  • Definition:

    • Similar to emulsions, but thicker.

    • Types: Oil-in-water (o/w) or water-in-oil (w/o).

  • Functionality:

    • O/w creams hydrate (vanishing cream) and occlude stratum corneum (SC).

    • W/o creams act as a barrier with a less greasy feel.

Page 17: Creams - Component Preparation

  • Preparation:

    • Emulsifiers may be added separately or as pre-blended emulsifying waxes.

    • Examples:

      • Aqueous Cream BP (30% Emulsifying Ointment BP, 1% Phenoxyethanol BP, Purified Water BP),

      • Cetrimide Cream BP (0.5% Cetrimide BP, 5% Cetostearyl alcohol BP).

Page 18: Gel-Network Theory of Emulsion Stability

  • Concept:

    • Cream consistencies controlled by structuring agents (rheological modifiers).

  • Mechanism:

    • Interactions in emulsifiers and water create lamellar gel networks, enhancing stability.

Page 19: Continued Gel-Network Stability

  • Explanation:

    • Mixed emulsifiers stabilize o/w lotions and creams while controlling consistency based on emulsifying wax concentration.

  • Importance of surface tension and interfacial film theories emphasized.

Page 20: Fatty Alcohol Mixed Emulsifiers

  • Role:

    • Combinations of fatty alcohols and ionic surfactants enhance swelling in aqueous phases.

    • Thickness of water layers can exceed hydrocarbon bilayers significantly.

Page 21: Interaction with Non-Ionic Surfactants

  • Effects:

    • Fatty alcohol swelling influenced by polyoxyethylene (POE) non-ionic surfactants.

    • Hydration and stabilization via steric repulsion occur in the interlamellar water.

Page 22: Compatibility Concerns in Formulations

  • Caution:

    • Watch for precipitation when mixing anionic and cationic surfactants.

    • Impacts drug activity, surfactant function, and formulation integrity (cracking).

Page 23: Closing Remarks

  • Gratitude:

    • Thank you for participation.

    • Questions?

Page 24: Summary of Formulations

  • Categories:

    • Hydrocarbon: Soft, hard and liquid paraffins; emollient effects; occlusive, dry skin only.

    • Absorption: Water absorption capacity, less greasy, emollient, suitable for weeping skin.

    • Emulsifying: Easily removable, non-staining; suitable for weeping skin.

    • Water Soluble: Greaseless, easily spread, lose consistency if >10% water.

Page 25: Detailed Examples of Emulsifying Ointments

  • Examples:

    • Various Emulsifying Ointments BP given specific formulations emphasizing types and proportions of ingredients.

Page 26: Additional Notes on Creams

  • Types of Creams:

    • Oil-in-water (o/w) and water-in-oil (w/o) formulations detailed with applications and formulation specifics.