Suppository bases are the vehicles that carry the active pharmaceutical ingredients in suppositories.
They can be classified into two main categories: lipophilic (fat-soluble) and hydrophilic (water-soluble) bases.
Each type of base has its advantages and disadvantages, and the choice of base depends on factors such as the drug's solubility, stability, and release characteristics.
1. Lipophilic bases:
a. Cocoa butter (Theobroma oil):
Cocoa butter is a natural fat obtained from cocoa beans and is the most widely used lipophilic base for suppositories.
It has a sharp melting point at around 34-36°C (93-97°F), which is slightly below body temperature.
Cocoa butter suppositories melt and release the drug when inserted into body cavities.
It is mainly used for rectal suppositories but can also be used for vaginal suppositories.
b. Hydrogenated vegetable oils:
Hydrogenated vegetable oils, such as palm kernel oil and cottonseed oil, are used as alternatives to cocoa butter.
They have similar melting points and physical properties but may offer better stability or compatibility with certain drugs.
c. Fatty acid esters:
Fatty acid esters, such as glyceryl monostearate and glyceryl monopalmitate, are synthetic lipophilic bases that can be used for suppositories.
They have varying melting points and can be selected based on the desired drug release characteristics.
2. Hydrophilic bases:
a. Glycerinated gelatin:
Glycerinated gelatin is a mixture of gelatin and glycerin, typically in a ratio of 1:2.
This base absorbs water and swells when inserted into body cavities, which helps release the drug.
Glycerinated gelatin suppositories are soft and pliable, making them suitable for vaginal and urethral administration.
b. Polyethylene glycols (PEGs):
PEGs are a family of water-soluble polymers that can be used as suppository bases.
They are available in various molecular weights and can be combined to achieve the desired melting point, solubility, and drug release characteristics.
PEG suppositories dissolve or erode upon contact with body fluids, releasing the drug.
c. Poloxamers:
Poloxamers are a class of nonionic surfactants that can be used as hydrophilic suppository bases.
They have a unique property called thermoreversible gelation, which means they form gels at body temperature.
Poloxamer suppositories are soft and have a high water content, making them suitable for vaginal or rectal administration.