Fatty Bases for Suppositories

Fatty Bases for Suppositories

They are designed to melt at body temperature. 

1. Theobroma Oil (Cocoa butter) 

It is a mixture of glyceryl esters of different unsaturated fatty acids. 

Cocoa Butter is a triglyceride, yellowish-white, solid, brittle fat, that smells and tastes like chocolate. Its melting point is between 30-35°C, its iodine value is "between" 34-38 and its acid value is not higher than 4, because cocoa butter can melt and rancid. So it must be stored in a cool dry place protected from light. 

Overheating changes its physical characteristics and it tends to adhere to the mold when solidified. It may exist in four crystalline states. 

α Form: This form is obtained by suddenly cooling the melted mass to 0°C. Its melting point is 24°C. 

β Form: This form is obtained when cocoa butter is melted at 35 to 36°C and slowly cooled. It melts at 18 to 23°C. 

β' Form: It reverts to 3 forms and melts at 34 to 35°C. 

γ Form: It is obtained by pouring a cool (20°C) cocoa butter into a container before it is solidified and cooled at deep-freeze temperature. It melts at 18°C.

All four forms are unstable and are converted to stable forms over several days. Thus, extreme care should be exercised while melting and cooling cocoa butter. In general, the minimal use of heat during the melting process is recommended. 

To overcome the drawbacks of cocoa butter, emulsified theobroma oil, hydrogenated palm kernel and soyabean oils have been suggested. 


• A melting range of 30 - 36°C (solid at room temperature but melts in the body). 

• Readily melted on warming, rapid setting on cooling. 

• Miscible with many ingredients. 

• Non-irritating. 


• Polymorphism: When melted and cooled it solidifies in different crystalline forms, depending on the temperature of melting, rate of cooling and the size of the mass. 

• If melted at not more than 36°C and slowly cooled it forms stable beta crystals with normal melting point. 

• If overheated and then cooled it produces unstable gamma crystals which melt at about 15°C or alpha crystals melting at 20°C. 

• Cocoa butter must be slowly melted over a warm water bath to avoid the formation of an unstable crystalline form. 

• Adherence to the mould. 

• Softening point too low for hot climates. 

• Melting point reduced by soluble ingredients. 

• Rancidity on storage. 

• Poor water-absorbing ability: Improved by the addition of emulsifying agents. 

• Leakage from the body. 

2. Emulsified Theobroma Oil 

When large quantities of aqueous solutions are required to be incorporated then emulsified theobroma oil as a base can be used. There are many agents which are used to form emulsified theobroma oil, for example: 2-3% cetyl alcohol, 4% glyceryl monostearate, 10% lanette wax, 4% beeswax, and spermaceti up to 12% can be utilised for emulsified theobroma oil suppositories. 

3. Hydrogenated Oils 

They are used as a substitute for theobroma oil, many hydrogenated oils are used as a substitute, for example, coconut oil, palm kernel oil, hydrogenated edible oil, and a mixture of oleic acid and stearic acid. They are known as synthetic fat bases.


The synthetic fat bases have advantages over theobroma oil are as follows: 

• Their solidifying points are unaffected by overheating. 

• Because of the lower content of unsaturated fatty acids they have good oxidation resistance. 

• The difference between melting and setting points is small. Hence, they set quickly, and the risk of sedimentation of suspended ingredients is low. 

• Lubrication of mould is not necessary because they contract significantly on cooling. 

• They are marketed in a series of grades with different melting point ranges, which can be chosen to suit particular products and climatic conditions. 

• They produce colourless, odourless and elegant suppositories. 

• They contain a proportion of w/o emulsifying agents, and therefore, their water-absorbing capacities are good. 


• Brittle if cooled rapidly, avoid refrigeration during preparation. 

• The melted fats are less viscous and more fluid than theobroma oil because of that there is a greater risk of drug particles to sediment during preparation.

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