Suppositories are formulated with various bases that provide the appropriate consistency, melting or dissolution characteristics, and compatibility with the active ingredients. The choice of base depends on factors such as the suppository’s intended use and the drug’s properties. Common types of bases for suppositories include:
1. Fatty or Oleaginous Bases
Examples: Cocoa butter (Theobroma oil), and hydrogenated vegetable oils.
Properties: These bases are solid at room temperature but melt at body temperature. They are suitable for drugs that are soluble or dispersible in lipids.
2. Water-soluble or Hydrophilic Bases
Examples: Polyethylene glycols (PEG), and glycerinated gelatin.
Properties: These bases are water-soluble and dissolve in body fluids. They are suitable for drugs that are water-soluble or require a rapid release.
3. Combination Bases
Examples: Polyethylene glycol and fatty acid esters.
Properties: These bases combine features of both oleaginous and hydrophilic bases, providing a balance of solubility and release characteristics.
4. Suppository Molds or Vehicles
Examples: Suppository molds made of plastic or metal.
Properties: Used for molding and shaping suppositories. The material should be inert, easy to clean, and withstand the suppository formulation.
5. Gelatin Bases
Examples: Gelatin, gelatin alcohol gels.
Properties: Gelatin bases are suitable for drugs that are sensitive to high temperatures. They are often used in rectal and vaginal suppositories.
6. Lipid-Based Bases
Examples: Witepsol, Suppocire.
Properties: These bases are composed of various lipids and offer various melting points. They are suitable for lipophilic drugs.
7. Polymeric Bases
Examples: Polyethylene oxide, polyethylene, polycarbophil.
Properties: These bases are used for controlled-release formulations and are suitable for various drugs.
8. Hydrophobic Bases
Examples: Stearic acid and cetyl alcohol.
Properties: Suppository formulations often combine these bases with other bases to provide structure and modify the release properties of the suppository.
The selection of a base depends on the drug’s specific requirements and the suppository’s therapeutic purpose. Formulators consider drug solubility, release kinetics, stability, and patient comfort when choosing the appropriate base for suppository formulation.
