Semi-solid Dosage Forms Overview

Semi-solid Dosage Forms

• Semi-solid dosage forms include ointments, pastes, creams, gels, plasters, and glycerogelatins.
• They are topically applied through the skin and are used for external applications.
• Ophthalmic ointments/gels are also available, and other routes include rectal, vaginal, and nasal administration.

Learning Objectives

• Enlist types of semi-solid dosage form and routes of administration.
• Enlist therapeutic uses of semi-solid dosage form.
• Explain dermatological preparation, discussing functions of topically applied semi-solids and providing three examples.
• Enlist six advantages and two disadvantages of semi-solid dosage forms.
• Discuss properties of semi-solid dosage forms.
• Understand ointment use, including both medicated and unmedicated ointments.
• Classify ointment bases, providing examples of four types (oleaginous, absorption, water-removable/emulsion, and water-soluble/water-miscible).
• Discuss drug incorporation in four types of ointment bases.
• Describe excipients used in semi-solid preparations.
• Describe two methods of ointment preparation and two techniques for mixing ingredients.
• Compare and contrast ophthalmic and topical ointment bases.
• Explain quality control, storage, packaging, labeling, and beyond-use dates (BUD) for ointments.
• Differentiate between ointments, pastes, creams, and gels.
• Compare four types of ointment bases.
• Discuss various terms associated with semi-solid dosage forms.

Properties of Semi-solid Dosage Forms

• Smooth texture, elegant appearance
• Non-dehydrating, non-greasy, non-staining.
• Non-gritty and non-irritating.
• Do not alter membrane/skin functioning.
• Miscible with skin secretion.

Ointments

• Intended for external application to skin or mucous membranes.
• Unmedicated ointments function as protectants, emollients, or lubricants. (Examples: cold cream, lip balm).
• Ointment bases serve as vehicles for medicated ointments used topically (e.g., for antipruritic, keratolytic, and astringent effects).

Ointment Bases

• Four types based on physical composition: oleaginous, absorption, water-removable/emulsion, and water-soluble/water-miscible.

• Oleaginous bases: hydrocarbon bases, used as emollients, occlusive dressings. Examples: White petrolatum, Yellow ointment

• Absorption bases: water-in-oil emulsions (can incorporate up to 50% water). Examples: hydrophilic petrolatum, Aquaphor.

• Water-removable/washable bases: oil-in-water emulsions (easily washed from skin). Example: Hydrophilic Ointment, USP.

• Water-soluble bases: do not contain oleaginous components. Example: Polyethylene glycol (PEG) ointment.

Creams

• Contain one or more medicinal agents in a W/O or O/W emulsion or water-washable base.
• Opaque, soft solids, or thick liquids for external application.
• Vanishing creams are oil-in-water emulsions with high water percentages.

Gels

• Semisolid systems of dispersions of inorganic particles in an aqueous liquid vehicle, rendered jellylike by a gelling agent.
• Gelling agents include synthetic macromolecules (e.g., carbomer 934, cellulose derivatives), and natural gums (e.g., tragacanth).
• Contains solvents (e.g., alcohol, propylene glycol).
• Contains preservatives (e.g., parabens) and stabilizers (e.g., edetate disodium).

Pastes

• Thick and stiff, do not flow at body temperature; larger proportion of solid material.
• Intended for application to the skin and absorb serous secretions.
• Example: Zinc oxide paste (Lassar's plain zinc paste).

Plasters

• Solid or semisolid adhesive masses spread on a backing (e.g., paper, fabric, moleskin, plastic).
• Applied to the skin for prolonged contact, protection, or mechanical support.
• Example: Salicylic acid plaster for removing corns.

Glycerogelatins

• Plastic masses containing gelatin, glycerin, water, and an added medicinal substance (e.g., zinc oxide).
• Melted before application, cooled slightly, and applied to the affected area.
• Example: Zinc gelatin boot used for varicose ulcers.

Practice Questions

• Multiple practice questions pertain to semi-solid preparations, their properties, advantages, disadvantages, components, manufacturing methods, uses, and various aspects related to quality control and storage.

Incorporation of Drugs

• Methods for incorporating various types of drugs into semi-solid bases.
• Levigating.
• Fusion.

Lab Scale and Large-Scale Equipment

• Methods for manufacturing semi-solid dosage forms.