Tablets

Tablets are the most commonly used solid dosage forms. They are best suited to large-scale production because of their low manufacturing cost, precision of the unit dose, and ease of packaging and shipping. Besides, they are the most stable of all oral dosage forms, they need less shelf space than liquids, and they are simple to identify and are essentially tamperproof. They are also most appropriate for special-release forms.

The tablets are manufactrured by wet granulation, dry granulation, or direct compression. Regardless of the method of manufacture, tablets for oral ingestion usually contain excipients, which are components added to the active ingredients that have special functions.

Diluents are fillers designed to make up the required bulk of the tablet when the drug dosage amount is inadequate. Diluents may also improve cohesion, permit direct compression, or promote glidance. Common diluents include kaolin, lactose, mannitol, starch, microcrystalline cellulose, powdered sugar, and others. Selection of the diluent is based on the cost of the diluent and its compatibility with the other tablet ingredients. For example, calcium salts cannot be used as fillers for tetracycline products because calcium interferes with the absorption of tetracycline from the gastrointestinal tract.

Binders and adhesives are added in either dry or liquid form to promote granulation or cohesion of ingredients during direct compression. Common binding agents include a 10-20% aqueous preparation of corn-starch, a 25-50% solution of glucose, various natural gums (e.g., acacia), and others. The proper amount of binder or adhesive is very important, because overwetting usually produces granules that are too hard, while underwetting usually produces tablets that are too soft and tend to crumble.

Disintegrants are added to tablet formulations to facilitate disintegration when the tablet is exposed to gastrointestinal fluid. Disintegrants function by drawing water into the tablet, swelling, and causing the tablet to burst. Common disintegrants include corn starch, potato starch, and their derivatives.

Lubricants, glidants, and antiadherents have overlapping functions. Lubricants and glidants reduce the friction and promote ejection of the tablet from the mold, as well as the flow of the tablet along the esophagus. Antiadherents reduce the sticking of the tablet in the tablet-making machine Talc. magnesium stearate, and calcium stearate are commonly used as lubricants.

Colours and dyes provide product identification, and produce a more aesthetic appearance of the product. Food, drug, and cosmetic dyes are applied as solutions. Flavouring agents are usually limited to chewable tablets or tablets intended for dissolving in the mouth. Some sweeteners or flavour oils may be added in the process of granulation.

Compressed tablets are manufactured by compression and have no special coating. Tablets may be coated for a number of reasons: to mask the taste, colour, or odour of the drug, to control drug release, to protect the drug from the acid medium in the stomach, to incorporate another drug and provide sequential release or avoid incompatibility, or to improve appearance.

Delayed-action and enteric-coated tablets delay the release of a drug from a dosage form. This delay is intended to prevent destruction of the drug by gastric juices, to prevent irritation of the stomach lining by the drug, or to promote absorption, which is better in the intestine than in the stomach. However, not all delayed-action tablets are enteric or are intended to produce an enteric effect.

Sugar-coated tablets are compressed tablets that are coated with coloured or uncoloured sugar. The process involves seal coating (waterproofing), subcoating, syrup coating (for smoothing and coloring), and polishing. These steps take place in a series of mechanically operated coating pans. Disadvantages of sugar-coated tablets include the time and expertise required for the process and the increase in the tablet size and weight. Sugar-coated tablets may be 50% larger and heavier than the original compressed tablet.

Film-coated tablets are covered with a thin layer of water-insoluble or water-soluble polymer (e.g., povidone). The film is usually coloured, and is more durable, less bulky, and less time-consuming than sugar-coating. Although the film increases tablet weight by 2-3%, it increases formulation efficiency, resistance to chipping, and output.

II.13. Переведите письменно абзацы 8 и 9 текста С.