Specifications of suppository bases
1- Chemical composition and origin: As the suppository bases may be extracted from a natural, synthetic, or modified natural origin, and the compatibility of the suppository bases appears physically and chemically with other components such as preservatives, antioxidants, and emulsifiers.
2- melting range: Suppository bases composed of triglycerides may not have a sharp melting point, and the melting range may be expressed by the temperature at which the fat begins to melt and the temperature at which the fat completely melts.
The lower the melting range, the greater the absorption of the drug from the suppository base.
3- Solidification Point: It is the point that allows the base of the suppositories to cool in order to harden the base, and the difference between the melting point and the solidification point must be 10 Celcius, in other words, if the melting point is 30 degrees Celsius, then the solidification point must be 20 degrees Celsius, but if the difference between melting and solidification increases Above 10 degrees Celsius, this may lead to a delay in cooling and solidification of the suppository in the mold, which leads to precipitation of the drug in the apex, which will contain all the drug content.
4- Hydroxyl value: the number of milligrams of potassium hydroxide that would neutralize the acetic acid used to acetylize 1g of fat.
5- Saponification Value: The number of milligrams of potassium hydroxide needed to neutralize the free fatty acids and saponify the ester present in 1 gram of fat , the saponification test for suppository bases is useful in knowing the quantity and type of glyceride used as mono-glyceride, di-glyceride or tri-glyceride.
6- Iodine Value: It is the number of grams of iodine that reacts with 100 grams of fat used in suppositories. The higher the value of iodine, the greater the possibility of rancidity of the fat.
7- Acid Value: It is the number of milligrams of KOH Potassium hydroxide required neutralizing the free fatty acids in I g substance of fat , the lower the acid value, the better the bases for suppositories, because this helps to reduce fat rancidity and reduces irritation.
8- Water number: It is the amount of water used to combine it with 100 grams of fat, and the number of water can be increased by adding surface active agents.