Semi-Solid Dosage Forms Lecture Notes

Overview

  • Semi-solid dosage forms include ointments, creams, gels, pastes, and plasters.
  • Application sites for these forms include dermal, ophthalmic, nasal, rectal, and vaginal routes.

Ointments

  • Definition: Semi-solid preparations for external application, can be medicated or unmedicated.
  • Uses:
    • Protectants
    • Emollients
    • Lubricants

Ointment Bases

  • Types:
    1. Oleaginous Bases (Hydrocarbon):
    • Emollient effects (occlusive).
    • Difficult to wash off.
    • Examples: Petrolatum, White Petrolatum.
    1. Absorption Bases:
    • Allow incorporation of aqueous solutions (form W/O emulsions).
    • Examples: Hydrophilic Petrolatum, Lanolin.
    1. Water-Removable Bases:
    • O/W emulsions, easily washed off, absorb serous discharge.
    • Example: Hydrophilic Ointment.
    1. Water-Soluble Bases:
    • No oleaginous components, greaseless, not ideal for incorporating aqueous solutions.
    • Example: Polyethylene Glycol Ointment.

Selection of Appropriate Base

Consider:

  • Desired release rate
  • Absorption method (topical vs. percutaneous)
  • Degree of occlusion of moisture
  • Stability of drug in base
  • Effect of drug on base consistency
  • Surface characteristics (e.g., dry or weeping skin).

Preparation of Ointments

  • Fusion: Melting and cooling components together.
  • Incorporation: Mixing until uniform, using geometric dilution and levigation for solids.
    • Note: Beware of absorption capacity when incorporating liquids.

Compendial Requirements

  • Microbial Content: Not sterile unless ophthalmic; must meet microbial standards, including preservatives for water-containing bases.
  • Minimum Fill: Ensures net weight/volume meets labeled amounts.
  • Packaging: Requires well-closed jars/tubes, light-sensitive products in resistant packaging.
  • Storage: Keep cool to prevent component separation.
  • Labeling: Must include base type indications for some ointments.

Creams

  • Definition: Semisolid preparations with medicinal agents in O/W or W/O emulsions.
  • Usage: Topical, vaginal, and rectal applications; favored for spreadability and ease of removal.
    • Vanishing Creams: High water content, leaving oily residues after evaporation.

Gels

  • Definition: Dispersions of molecules in an aqueous vehicle, thickened by gelling agents.
  • Types:
    1. Single Phase: Uniform macromolecule distribution.
    2. Two Phase: Distinct particle floccules (magma).
  • Characteristics: May thicken on standing, requiring shaking for use.

Miscellaneous Semi-solids

  • Pastes: High solid content (25%); stiffer than ointments; used to absorb secretions.
  • Plasters: Adhesive solid or semi-solid masses for applied prolonged contact.
  • Glycerogelatins: Contain gelatin, glycerin, and medicinal agents for longer effects.
  • Liquid Bandage: Creates a protective layer on the skin using polymers for wound protection.

Specific Applications

  • Dermal Application: Drugs designed for skin delivery.
  • Ophthalmic Preparations: Used for eye conditions; require strict sterility and comfort.
  • Nasal Preparations: Deliver medications locally to nasal mucosa, rich vascular supply.
  • Rectal Preparations: For local conditions and can be systemically absorbed under specific circumstances.
  • Vaginal Preparations: Used for infections and contraception.

End of Lecture

  • Review and understand each dosage form and preparation method for the exam.