Solid dosagesSolid dosages, such as tablets, have many advantages over other types: greater stability, lesser risk of chemical interreaction between different medicaments, smaller bulk, accurate dosage, and ease of production. Powders intended for internal use are usually mixtures of two or more ingredients. If two ingredients are present in unequal quantities, then the lesser ingredient (usually the drug substance) is mixed with an equal weight of the greater ingredient. Next, the resulting mixture is combined with an equal weight of the greater ingredient in steps until the mixture is homogeneous and complete. This process of geometric dilution is essential in order to produce a homogeneous powder. Cachets, occasionally used for administration of powdered drugs with unpleasant taste, consist of shells made of gelatinized starch paste. More common today is the hard capsule, in which the powder is enclosed in a shell of hard gelatin. Semi-liquid and liquid drugs are often enclosed in a soft capsule with a soft gelatin shell. Before the machine-made compressed tablet, pills were a very popular solid dosage form. Today, pills are rarely prescribed, though some popular types are manufactured by machine. The powdered ingredients are mixed together with a binding agent, such as tragacanth or acacia, and are then made into a plastic mass by incorporation of an appropriate liquid drug and addition of an inert liquid. The resulting mass, known as the pill mass, is then rolled into spheres and coated with talk, gelatin, or sugar. Tablets, by far the most common method of administration of drugs, are only rarely made by compression of the drug alone (e.g., potassium bromide tablets). Usually, the drug is mixed with suitable diluents, such as dextrin, lactose, salt, starch, or synthetic substances, designed to ensure disintegration of the tablet in the body. To prevent sticking in the machine, a lubricant such as liquid paraffin, stearic acid, talk, or a synthetic substance is usually added. It is essential that the tablet machines are fed with the drug mixture in a free-flowing form to ensure complete filling of the molds. To achieve that, the drug mixture is granulated by mechanically forcing pellets of the mixture through a sheet of perforated metal. The granulated mixture is then fed into the tablet machine which feeds the correct dose into the mold, and the mixture is compressed. Excessive compression may mean that the tablet will not disintegrate in the body, while insufficient compression results in fragile tablets that may break, causing inaccurate dosage. Coatings of various types may be applied onto the tablet in order to protect the ingredients from deterioration, to hide the taste of certain drugs, to control the release of the drug from the tablet, or to produce a more attractive tablet. In the manufacture of layered tablets, incorporating two or more drugs, a compressed tablet is fed into a second machine where another layer is compressed around it. In this way, drugs normally incompatible may be formulated in the same tablet. Other solid dosages include troches and dry extracts. Troches, also known as lozengers or pastilles, disintegrate or dissolve in the mouth, slowly releasing the active drug. The base usually consists of a mixture of sugar and gum and gelatin. Lozengers are generally manufactured by compression techniques, while pastilles are fabricated by fusion and the use of molds. Dry extracts are usually granulated by being passed through a sieve and may be used for the preparation of tablets.
II.3. Найдите в тексте ответы на следующие вопросы.
1. What advantages do the solid dosage forms have? 2. What method is generally used in making powders if the drug is being mixed with a bulky ingredient? 3. Which solid dosage form is especially suitable for the preparation of solutions from the drugs unstable in the presence of water? 4. Which of the solid dosages is rarely used today and why? 5. Why are diluents added in the process of drug tabletting? 6. What is the function of lubricants in the process of tabletting? 7. Why is proper compression so important in tablet-making? 8. What is the purpose of applying different coatings onto the tablets? 9. How can incompatible drugs be formulated in the same tablet? 10. What are the drugs like lozengers designed for?
II.4. Найдите в тексте А эквиваленты следующим словам и словосочетаниям:
преимущества перед; точная дозировка; предназначенный для внутреннего применения; поэтапно; разбавление в геометрической прогрессии; однородный (гомогенный) порошок; порошковые лекарства с неприятным вкусом; оболочки, сделанные из желатинизированного крахмала; жёсткая (твёрдая) капсула; полужидкий; прессованная таблетка фабричного изготовления; пилюльная масса; подходящие разбавители; для предотвращения застревания в машине; смазка; подавать точную дозу в формочку; недостаточное / чрезмерное прессование; наносить оболочку на таблетку; плавление.
II.5. Найдите в правой колонке синонимы для слов и выражений из левой колонки слов.
cachet to hide administration lozengers rarely to be intended for often capsule to incorporate use to be designed for seldom to disintegrate commonly to mask to add troches to decompose
II.6. Найдите под чертой антонимы для следующих слов и выражений:
greater, solid, advantages, homogeneous, internal, rarely, inert, common, synthetic, correct, initial, ease, soft
external, liquid, final, difficulty, lesser, disadvantages, often, hard, wrong, active, rare, heterogeneous, natural, commonly
II.7. Образуйте от этих слов слова с противоположным значением с помощью приставок un-, in-, dis-, im-, ir-
accurate, regular, common, advantage, miscible, soluble, pleasant, sufficient, compatible, equal, complete, stable, correct
II.8. Ознакомьтесь со словами к тексту B.
II.9. Просмотрите текст B и найдите в нём 10 предложений c разными типами придаточных предложений. Переведите их на русский язык. II.10. Прочтите текст В и назовите 3 основных типа фармацевтических порошков и 4 способа их приготовления.
Text B
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