In general, tablets are composed of two major types of substances, one is the drug that plays a therapeutic role (ie, the main drug), and the other is a substance that has no physiological activity. Their main functions include: filling Actions, adhesions, disintegration and lubrication, sometimes also play a role in coloring, flavoring, and aesthetics. In pharmacy, these substances are often referred to as excipients or Adjuvants. Depending on how they work, excipients are often divided into four categories.
The main function of the diluent (or filler, Fil1ers) is to fill the weight or volume of the tablet, thereby facilitating tableting; commonly used fillers are starch, sugar, cellulose and inorganic salts; It is determined by factors such as tableting process and preparation equipment. The diameter of the tablet is generally not less than 6 mm, and the tablet weight is more than 100 mg. If the main drug in the tablet is only a few milligrams or tens of milligrams, no suitable filler is added. It will not be able to make tablets, so the diluent plays an important role here and increases the volume to help it form.
More commonly used is corn starch, its properties are very stable, and most drugs do not work, the price is relatively cheap, low hygroscopicity, good appearance and color, in actual production, often with good pressure powder, Dextrin is used in combination because the compressibility of starch is poor, and if used alone, the pressed tablets are too loose.
2. Powdered sugar
Sugar powder refers to a white powder obtained by crystallizing sucrose by low-temperature drying and pulverization. It has the advantages of strong adhesion, can be used to increase the hardness of the tablet, and makes the surface of the tablet smooth and beautiful. The disadvantage is that the hygroscopicity is strong. Long-term storage will make the hardness of the tablet too large, and it will be difficult to disintegrate or dissolve. In addition to the buccal tablets or soluble tablets, it is generally not used alone, and is often used in combination with dextrin and starch.
Dextrin is a general term for starch hydrolysis intermediates. Its chemical formula is (C6H10O5)nÂ·XH2O. Its water-soluble content is about 80%. It dissolves slowly in cold water, is more soluble in hot water, and is insoluble in ethanol. It is also known as high paste (high viscosity dextrin), that is, it has strong cohesiveness. Improper use may cause pitting on the one side, watermarking or causing disintegration or dissolution of the tablet. Similarly, in the content If the extraction is not sufficiently pulverized during the measurement, the accuracy and reproducibility of the measurement result will be affected. Therefore, the dextrin is rarely used as a filler in a large amount, and is often used in combination with the powdered sugar and starch.
Lactose is an excellent tablet filler, which is extracted from bovine whey and is widely used in foreign countries. However, due to its high price, it is not widely used in China. It is commonly used as crystalline lactose (ie Î±-aqueous lactose) containing one molecule of water. It has no hygroscopicity, good compressibility and stable properties. It does not chemically react with most drugs. The pressed tablets are smooth and beautiful. The spray-drying method is used. Lactose is non-crystalline lactose, which has good fluidity and compressibility, and can be used for direct compression of powder.
5. Compressible starch
Also known as Pregelatinized starch, it is a new type of pharmaceutical excipient. It has been collected in English, American, Japanese and Chinese Pharmacopoeia. It was successfully developed in China in 1988 and is now available in large quantities. Domestic compressible starch is a partially pre-gelatinized product (full pre-gelatinized starch, also known as alpha-starch), which is equivalent to Starch RX1500 from Colorcon, a foreign company. This product is a multi-functional auxiliary material, which can be used as a filler. It has good fluidity, compressibility, self-lubricity and dry adhesion, and has good disintegration effect. If it is used for direct compression of powder, the amount of magnesium stearate should not exceed 0.5% to avoid softening effect.
6. Microcrystalline cellulose
Microcrystalline cellulose (MCC) is a crystalline cellulose with a small degree of polymerization obtained by partial hydrolysis of cellulose. It has good compressibility and strong binding force. It has a high hardness and can be used as a "dry binder" for direct compression of powder. The foreign product is called Avicel and has several specifications depending on the particle size. Domestic microcrystalline cellulose has been widely used in China, but its quality needs to be further improved, and the product variety needs to be enriched. In addition, disintegration is preferred when the tablet contains 20% microcrystalline cellulose.
7. Inorganic salts
Mainly some inorganic calcium salts, such as calcium sulfate, calcium hydrogen phosphate and medicinal calcium carbonate (made by sedimentation method, also known as precipitated calcium carbonate). Among them, calcium sulfate is commonly used, its properties are stable, odorless and tasteless, slightly soluble in water, and can be compatible with various drugs. The prepared tablets have a smooth appearance, good hardness and disintegration, and no adsorption to drugs. Calcium sulfate dihydrate is often used in tablet excipients. However, it should be noted that calcium sulfate interferes with the absorption of certain main drugs (tetracyclines) and should not be used at this time.
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