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7. Tablets Contents 1. 2. 3. 4. 5. 6. Types of tablets Compressed tablets Chewable tablets Molded tablets Tablet coating Impact of manufacturing changes on solid dosage forms 7. Official and commercially available tablets 8. Packaging and storing tablet Tablets are solid dosage forms usually prepared with the aid of suitable pharmaceutical excipients. • Tablets may vary in size, shape, weight, hardness, thickness, disintegration, and dissolution characteristics and in other aspects, depending on their intended use and method of manufacture. • Tablets can be administered orally, sublingually, buccally, or vaginally. • Tablets are prepared primarily by compression, with a limited number prepared by molding. 1. Types of tablets 1) Compressed tablets • Medicinal agent • Diluents or fillers, which add the necessary bulk to a formulation to prepare tablets of the desired size. 淀粉(starch) • 白色粉末、无臭、无味、不溶于水 • 迅速吸收空气中的水分，通常含水量在 1014%范围 • 具有黏附性、粉体流动性与可压性较差 • 性质稳定、与大多数药物配伍 • 外观色泽好，价格便宜 • 常与可压性较好的蔗糖粉、糊精等混合 使用。 蔗糖(sucrose) • 白色、无臭、有甜味、极易吸湿、溶于水、不 溶于乙醇 • 在温度110145C时，或在酸性条件下引起糖转 化（葡萄糖和果糖），在室温和中等湿度条件 下稳定 • 粘合力强，可用来增加片剂的硬度，常与糊精、 淀粉配合使用 • 应注意片剂长期贮存过程中由于蔗糖的吸湿和 干燥使片剂的硬度变大，崩解或溶出不合格等 问题 • 治疗糖尿病或其他糖代谢不良症的药物制剂中 不宜加入。 乳糖(lactose) • 常用的乳糖是含有一分子结晶水的-乳糖 • 白色结晶性粉末、无臭、微甜，水中微溶，在 乙醇中几乎不溶 • 无吸湿性，可压性较好，压成的药片光洁美观， 性质稳定，可与大多数药物配伍。 • 有喷雾干燥法制得的乳糖为非结晶性、球形乳 糖，其流动性、可压性良好，可供粉末直接压 片。 预胶化淀粉(pregelatinized starch) • 白色粉末、无臭、微有特殊口感，在水 中可溶10%-20% • 本品具有良好的流动性、可压性、自身 润滑性和干粘合性，并有较好的崩解作 用。 • 作为多功能辅料，常用于粉末直接压片 微晶纤维素(microcrystalline cellulose) • 本品为白色无味的多孔性颗粒状粉末 • 具有较强的结合力与良好的可压性，亦有 干粘合剂之称 • 具有崩解作用（吸水膨胀，高于20％） • 压缩成型性很好，可用于粉末直接压片。 无机盐类： • 磷酸氢钙、碳酸钙及硫酸钙等。其中二 水硫酸钙较为常用，其性质稳定，无臭、 无味，微溶于水，可与多种药物配伍 • 制成的片剂外观光洁，硬度、崩解度均 好，对药物也无吸附作用。 • 甘露醇 (mannitol)： - 本品为六碳醇，山梨醇的异构体，为白 色细微粉末，甜度与葡萄糖相近，性质 稳定，安全性好，吸湿性差（CRH为85 ％），可压性良好。 - 本品可溶于水，溶解时吸热有凉爽感， 适于口含片及舌下片。 Binders or adhesives, • which promote the adhesion of the particles of the formulation, enabling a granulation to be prepared and the maintenance of the integrity of the final tablet. • 蒸馏水 （distilled water) 当原、辅料有一定粘性时，加入水可制 成性能符合要求的颗粒。 乙醇(ethanol)： • 当药物遇水能引起变质，或用水为润湿剂制成 的软才粘性太强而较难制粒，或制成的干颗粒 太硬时，可选用适宜浓度的乙醇为润湿粘合剂。 • 乙醇浓度越高，则润湿后产生的粘性越小，制 的的颗粒较松散，片剂崩解较快。常用浓度为 30-70%。 • 乙醇溶液作润湿剂时，应迅速混合进行制粒并 迅速干燥，避免乙醇挥发而使软材结团不易制 粒，或使已制得的颗粒变性结团。 淀粉浆： • 是将淀粉混悬于水中在一定温度下的糊 化物，玉米淀粉糊化温度约70～75C。 • 粘合作用良好，国内外应用广泛，浓度 5～15％，常用10％。 • 淀粉浆能均匀的润湿辅料，不易出现局 部过湿现象，不影响制剂的崩解与溶出 以及药物测定。 纤维素衍生物 甲基纤维素(methylcellulose, MC)： • 在冷水中溶解，在热水及乙醇中几乎不溶。 • 应用于水溶性和水不溶性物料的制粒中，颗粒压 缩成形性好、且不随时间变硬。 羟丙基纤维素(hydroxypropylcellulose, HPC)： • 在低于38C水中可混溶形成润滑透明的胶体溶液， 加热至50C形成高度溶胀的絮状沉淀。 • 既可做湿法制粒的粘合剂，也可做粉末直接压片 的干粘合剂。 羟丙甲基纤维素（hydroxypropylmethylcellulose,HPMC）: • 溶于冷水，不溶于热水与乙醇，但在水和乙醇的混合液 中溶解。 • 用量一般占配方量的1～4％ • 压制成的片剂外观硬度和溶出度均良好。 羧甲基纤维素钠(carboxymethylcellulose sodium,CMCNa)： • 在任何温度的水中易分散、溶解，形成透明的胶状溶液。 • 常用于可压性较差的药物 • 通常含水量少于10%，在高湿条件下可以吸收大量的水（〉 50%），这一性质在片剂的贮存过程中会改变片剂硬度和 崩解时间。 聚维酮（povidine,PVP) • 可溶于水，适宜浓度的水溶液为粘合剂，其用 量常占片剂总重的0.52%。 • 也可溶于乙醇，并可用其醇溶液为润湿粘合剂， 因此较适于对水敏感的药物； • 也适用于疏水性药物，有利于润湿药物易于制 粒，又因改善了药物的润湿性而有利于药物溶 出。 • 一步制粒机制粒的良好粘合剂。 • 是溶液片、泡腾片、咀嚼片等的优良粘合剂 Disintegrants • which promote the breakup of the tablets after administration to smaller particles for more ready drug availability; 干淀粉： • 最常用的一种崩解剂，用量一般为配方总量 5%20%，崩解作用较好； • 用量不宜太多，压缩成型性不好； • 对不溶性药物或微溶性药物较适用； • 水杨酸钠、对氨基水杨酸钠可使淀粉胶化，故可 影响其崩解作用； • 用量太多，影响颗粒的粒度分布，因而影响片重 差异。 羧甲基淀粉钠（sodium carboxymethyl starch, CMS-Na)： • 吸水膨胀作用显著，其吸水后膨胀率为原 体积的300倍 • 性能优良的崩解剂 低取代羟丙基纤维素（low-substituted hydroxypropylcellulose, L-HPC）： • 近年来国内应用较多的一种崩解剂 • 具有很大的表面积和空隙率 • 有很好的吸水速度和吸水量 交联羧甲基纤维素钠（croscarmellose sodium, CCNa）： • 由于交联键的存在不溶于水，可吸水并有较强 的膨胀作用， • 具有较好的崩解作用， • 与羧甲基淀粉钠合用时崩解效果更好，但与干 淀粉合用时崩解作用降低。 交联聚维酮（crospovidone, PVPP）： • 是流动性良好的白色粉末，在水中不溶，但在 水中迅速溶胀，无粘性，因而崩解性能优越， • 用量较L-HPC等少， • 本品为崩解剂的片剂崩解时间受压片力的影响 较小。 • Glidants or lubricants which enhance the flow of the tableting material into the tablet dies, minimize wear of the punches and dies, prevent the sticking of fill material to the punches and dies and produce tablets having a sheen. 硬脂酸镁(magnesium stearate)： • 润滑作用良好 • 可显著地降低片剂的推片力 • 有防止粘冲作用 • 压片后片面光滑美观 • 用量0.11% • 由于本品为疏水性物质，用量过大，影 响片剂的崩解 滑石粉(talc)： • 为优良助流剂，可用于抗粘剂和润滑剂 • 减低颗粒表面的粗燥性，从而达到降低颗粒间 的摩擦力，改善颗粒的流动性 • 一般用量0.13% 微粉硅胶(fumed silicon dioxide)： • 为轻质白色无水粉末，比表面积大，对液体药 物及挥发油有一定的吸收性， • 为优良的助流剂，可用于粉末直接压片， • 用量0.10.3% Colorants and flavorants • 应符合药用规格，口服所用色素必须是 药用级或食用极 • 色素最大用量一般不超过0.05% • 把色素先吸附于硫酸钙、三磷酸钙、淀 粉等主要辅料中可有效地防止颜色的迁 移 • 香精的加入方法是将香精溶解于乙醇中， 均匀喷洒在已经干燥的颗粒上。 2) Multiply compressed tablets • Multiply compressed tablets are prepared by subjecting the fill material to more than a single compression. • Layered tablets are prepared by initial compaction of a portion of fill material in a die followed by additional fill material and compression to form two- or threelayered tablets, depending on the number of separate fills. 3) Sugarcoated tablets • Compressed tablets may be coated with a colored or an uncolored sugar layer. • The sugarcoat protects the enclosed drug from the environment and provides a barrier to objectionable taste or odor. • The sugarcoat also enhances the appearance of the compressed tablet. Disadvantages: The time and expertise required in the coating process and the increase in size, weight, and shipping costs. 4) Film-coated tablets • Film-coated tablets are compressed tablets coated with a thin layer of a polymer capable of forming a skinlike film over the tablet. • The film is usually colored and has the advantage over sugarcoatings in that it is more durable, less bulky, and less time consuming to apply. 5) Gelatin-coated tablets A recent innovation is the gelatincoated tablet. The innovator product, the gelcap, is a capsule-shaped compressed tablet that allows the coated product to be about one-third smaller than a capsule filled with an equivalent amount of powder. 6) Enteric-coated tablets • Enteric-coated tablets have delayed-release features. • They are designed to pass unchanged through the stomach to the intestines, where the tablets disintegrate and allow drug dissolution and absorption and/or effect. • Enteric coatings are employed when the drug substance • is destroyed by gastric acid, • is particularly irritating to the gastric mucosa, • when bypass of the stomach substantially enhances drug absorption. 7) Buccal and sublingual tablets • Buccal and sublingual tablets are flat oval tablets intended to be dissolved in the buccal pouch or beneath the tongue for absorption through the oral mucosa. • They enable oral absorption of drugs that are destroyed by the gastric juice and/or are poorly absorbed from the gastrointestinal tract. • Buccal tablets are designed to erode slowly, whereas those for sublingual use dissolve promptly and provide rapid drug effects. 8) Chewable tablets • Chewable tablets, which have a smooth, rapid disintegration when chewed or allowed to dissolve in the mouth, have a creamy base, usually of specially flavored and colored mannitol. • Chewable tablets are especially useful for administration of large tablets to children and adults who have difficulty swallowing solid dosage forms. 9) Effervescent tablets • Effervescent tablets are prepared by compressing granular effervescent salts that release gas when in contact with water. 10) Molded tablets • Certain tablets, such as tablet triturates, may be prepared by molding rather than by compression. The resultant tablets are very soft and soluble and are designed for rapid dissolution. 11) Tablet triturates • Tablet triturates are small, usually cylindrical, molded or compressed tablets containing small amounts of usually potent drugs. 12) Immediate-release tablets • Immediate-release tablets are designed to disintegrate and release their medication with no special rate-controlling features, such as special coatings and other techniques. 13) Instantly disintegrating or dissolving tablets • Instant-release tablets are characterized by disintegrating or dissolving in the mouth within 1 minute, some within 10 seconds. • Tablets of this type are designed for pediatric and geriatric patients or for any patient who has difficulty in swallowing tablets. • A number of techniques are used to prepare these tablets involving lyophilization, soft direct compression, and other methods. 14) Extended release tablets • Extended-release tablets are designed to release their medication in a predetermined manner over an extended period of time. 15) Vaginal tablets • Vaginal tablets, also called vaginal inserts, are uncoated and bullet- or ovoid-shaped tablets which are inserted into the vagina for localized effects. • They are prepared by compression and shaped to fit snugly on plastic inserter devices which accompany the product. 2. Compressed tablets Tablets diameters and shapes are determined by the die and punches used in the compression of the tablet. 1) Compressed tablet manufacture Compressed tablets may be made by three basic methods: - wet granulation - dry granulation - direct compression • • • • • • • Wet granulation is a widely employed method for the production of compressed tablets. The steps required are: weighing and blending the ingredients preparing a damp mass screening the damp mass into pellets or granules drying the granulation sizing the granulation by dry screening adding lubricant and blending tableting by compression ① Weighing and blending Specified quantities of active ingredient, diluent or filler, and disintegrating agent are mixed by mechanical powder blender or mixer until uniform. The fillers used are - Lactose (solubility, compatibility) - Microcrystalline cellulose (compactability, compatibility, and the consistent uniformity) - Starch - Powdered sucrose - Calcium phosphate Disintegrating agents include - Croscarmellose （交联羟甲纤维素） - Corn and potato starches - Sodium starch glycolate （甘醇酸酯淀粉钠） - Sodium carboxymethylcellulose （羧甲纤维素 钠） - Polyvinyl polypyrolidone (PVP) - Crospovidone - Cation-exchange resins - Alginic acid （海藻酸） ② Preparing the damp mass • A liquid binder is added to the powder mixture to facilitate the adhesion of the powder particles. • A damp mass resembling dough is formed and is used to prepare the granulation. • A good binder results in appropriate tablet hardness and does not negatively impact on the release of the drug from the tablet. ③ Screening the damp mass into pellets or granules The wet mass is pressed through a screen (usually No. 6- or 8-mesh) to prepare the granules. ④ Drying the granulation Granules may be dried in thermostatically controlled ovens which constantly record the time, temperature, and humidity. ⑤ Sizing the granulation by dry screening • After drying, the granules are passed through a screen of a smaller mesh than that used to prepare the original granulation. • In general, the smaller the tablet to be produced, the smaller are the granules used. • Sizing of the granules is necessary so that the die cavities for tablet compression may be completely and rapidly filled by the free-flowing granulation. • Voids or air spaces left by too large a granulation would result in the production of uneven tablets. ⑥ Adding lubrication and blending • After dry screening, a dry lubricant is dusted over the spread-out granulation through a fine mesh screen. • • • • Lubricants contribute to the preparation of compressed tablets in several ways: They improve the flow of the granulation in the hopper to the die cavity; They prevent the adhesion of the tablet formulation to the punches and dies during compression; They reduce friction between the tablet and the die wall during the tablet’s ejection from the tablet machine; They give a sheen to the finished tablet. The more commonly used lubricants are - Magnesium stearate - Calcium stearate - Stearic acid - Talc - Sodium stearyl fumarate （富马酸硬脂酸钠） The quantity of lubricant used from about 0.1% to 5% of the weight of the granulation. All-in-one granulation methods Technologic advances now allow the entire process of granulation to be completed in a continuous fluid-bed process, using a single piece of equipment, the fluid-bed granulator. The fluid-bed granulator performs the following steps: - preblending the formulation powder in a bed by fluidized air, - granulating the mixture by spraying onto the fluidized powder bed, a suitable liquid binder, as an aqueous solution of acacia, hydroxypropyl cellulose, or povidone, - drying the granulated product to the desired moisture content. Dry granulation • By the dry granulation method, the powder mixture is compacted in large pieces and subsequently broken down or sized into granules. • By this method, either the active ingredient or the diluent must have cohesive properties. Dry granulation is especially applicable to materials that can not be prepared by wet granulation due to their degradation by moisture or by the elevated temperatures required for drying the granules. ① Slugging ② Roller compaction Direct compression tableting • Some granular chemicals, like potassium chloride, possess free flowing and cohesive properties that enable them to be compressed directly in a tablet machine without need of wet or dry granulation. • For chemicals that do not possess this quality, special pharmaceutical excipients may be used which impart the necessary qualities for the production of tablets by direct compression. 2) Quality standards and compendial requirements • • • • • In addition to the apparent features of tablets, tablets must be met other physical specifications and quality standards. These include criteria for tablet weight, weight variation content uniformity, thickness tablet hardness tablet disintegration drug dissolution • These factors must be controlled during production (in-process controls) and verified after the production of each batch to assure that established product quality standards are met. ① Tablet weight and USP weight variation test • The quantity of fill placed in the die of a tablet press determines the weight of the resulting tablet. • The volume of fill is adjusted with the first few tablets produced to yield tablets of the desired weight and content. • The USP contains a test for the determination of dosage-form uniformity by weight variation for uncoated tablets. • In the test, 10 tablets are weighed individually and the average weight calculated. • The tablets are assayed and the content of active ingredient in each of the 10 tablets is calculated assuming homogeneous drug distribution. ② Content uniformity • By the USP method, 10 dosage units are individually assayed for their content according to the assay method described in the individual monograph. • The requirements for content uniformity are met if the amount of active ingredient in each dosage unit lies within the range of 85% to 115% of the label claim and the relative standard deviation is less than 6.0%. ③ Tablet thickness - The thickness of a tablet is determined by the diameter of the die, the amount of fill permitted to enter the die ， the compactability of the fill material ， and the force or pressure applied during compression. - To produce tablets of uniform thickness During batch production and between batch productions for the same formulation, care must be exercised to employ the same factors of fill, die, and pressure. ④ Tablet hardness and friability • Generally, the greater the pressure applied, the harder the tablets, although the characteristics of the granulation also has a bearing on tablet hardness. • Tablets should be sufficiently hard to resist breaking during normal handling and yet soft enough to disintegrate properly after swallowing. • Special dedicated or multifunctional to measure the required to break hardness testers systems are used degree of force a tablet. • A force of about 4 kilograms is considered the minimum requirement for a satisfactory tablet. • A tablet’s durability may be determined through the use of a friabilator. This apparatus determines the tablet’s friability. • A maximum weight loss of not more than 1% of the weight of the tablets being tested generally is considered acceptable for most products. 第七节 片剂的质量检查 ⑤ Tablet disintegration • Tablet disintegration is important for tablets containing medicinal agents (such as antacids and antidiarrheals) that are not intended to be absorbed but rather to act locally within the gastrointestinal tract. • In these instances, tablet disintegration provides drug particles with an increased surface area for localized activity within the gastrointestinal tract. • Tablets usually must disintegrate 30 minutes, but varying from about 2 minutes for Nitroglycerin Tablets to up to 4 hours for buccal tablets • If one or more tablets fail to disintegrate, additional tests prescribed by the USP must be performed. • Enteric-coated tablets are similarly tested, except that the tablets are permitted to be tested in simulated gastric fluid for one hour after which no sign of disintegration, cracking, or softening must be seen. ⑥ Tablet dissolution In vitro dissolution testing of solid dosage forms is important for a number of reasons. - It guides the formulation and product development process toward product optimization. - The performance of the manufacturing process may be monitored by dissolution testing. - Consistent in vitro dissolution testing results assure bioequivalence from batch-to-batch. - As a requirement for regulatory approval for product marketing for products registered with the FDA and regulatory agencies of other countries. A system has been developed which relates combinations of a drug’s solubility (high or low) and its intestinal permeability (high or low) as a possible basis for predicting the likelihood of achieving a successful in vivo-in vitro correlation (IVIVC). • • • • High solubility and high permeability Low solubility and high permeability High solubility and low permeability Low solubility and low permeability For a high solubility and high permeability drug, an IVIVC may be expected if the dissolution rate is slower than the rate of gastric emptying. • In the case of a low solubility and high permeability drug, drug dissolution may be the rate limiting step for drug absorption and an IVIVC may be expected. • In the case of a high solubility and low permeability drug, permeability is the rate-controlling step and only a limited IVIVC may be possible. • In the case of a drug with low solubility and low permeability, significant problems would be likely for oral drug delivery. • • • • A number of formulation and manufacturing factors can affect the disintegration and dissolution of a tablet including: The particle size of the drug substance in the formulation; The solubility and hygroscopicity of the formulation; The type and concentration of the disintegrant, binder, and lubricant used; The manufacturing method, particularly the compactness of the granulation and the compression force used in tableting. 3. Chewable tablets • Chewable tablets are pleasant tasting tablets formulated to disintegrate smoothly in the mouth with or without active chewing. • They are prepared by wet granulation and compression, using only minimal degrees of tableting pressure in order to produce a soft tablet. • Mannitol, a white crystalline hexahydric alcohol, is used as the excipient in most chewable tablets. Per tablet • Aluminum hydroxide 325.0mg • Mannitol 812.0mg • Sodium saccharin 0.4mg • Sorbitol 32.5mg • Magnesium stearate 35.0mg • Mint flavor concentrate 4.0mg Preparation: Blend the aluminum hydroxide, mannitol, and sodium saccharin. Prepare a wet granulation with the sorbitol solution. Dry at 120C and screen through a 12-mesh screen. Add the flavor and magnesium stearate, blend, and compress into tablets. 4. Molded tablets • Commercial preparation of tablets by molding has been replaced by tablet compression. • Molded tablets, or tablet triturates, may be prepared on a small laboratory scale. Molded tablets are intended to dissolve rapidly in the mouth. They are not contain disintegrants, lubricants, or coatings to slow their rate of dissolution. 5. Tablet coating • • • • Tablets are coated for a number of reasons, including to protect the medicinal agent against destructive exposure to air and/or humidity; to mask the taste of the drug; to provide special characteristics of drug release; to provide aesthetics or distinction to the product. 1) Sugarcoating tablets The sugarcoating of tablets may be divided into the following steps: - waterproofing and sealing, - subcoating, - smoothing and final rounding, - finishing and coloring if desired, - polishing. Waterproofing and sealing coats • For tablets containing that may be adversely affected by moisture, one or more coats of a waterproofing substance, such as pharmaceutical shellac or a polymer, is applied to the compressed tablets before the subcoating application. • The waterproofing solution is gently poured or sprayed on the compressed tablets rotating in the coating pans. • Warm air is blown into the pan during the coating to hasten the drying and to prevent tablets from sticking together. Subcoating • After the tablets are waterproofed if needed, three to five subcoats of a sugar-based syrup are applied. • This bonds the sugar coating to the tablet and provides rounding. • The sucrose and water syrup also contains gelatin, acacia, or polyvinylpyrrolidone (PVP) to enhance coating. • When the tablets are partially dry, they are sprinkled with a dusting powder, usually a mixture of powdered sugar and starch but sometimes talc, acacia, or precipitates chalk as well. • Warm air is applied to the rolling tablets, and when they are dry, the process is repeated until the tablets are of the desired shape and size. Smoothing and final rounding • After the tablets are subcoated, 5 to 10 additional coatings of a thick syrup are applied to complete the rounding and smooth the coatings. • A dusting powder is often used between syrup applications. • Warm air is applied to hasten the drying time of each coat. Finishing and coloring • To attain final smoothness and the appropriate color to the tablets, several coats of a thin syrup containing the desired colorant are applied in the usual manner. • This step is performed in a clean pan, free from previous coating material. Imprinting • Solid dosage forms may be passed through a special imprinting machine to impart identification codes and other distinctive symbols. Polishing Coated tablets may be polished in several ways - Special drum-shaped pans or ordinary coating pans lined with canvas or other cloth impregnated with carnauba wax and/or beeswax, may be used to polish tablets as they tumble in the pan. - Pieces of wax may be placed in a polishing pan and the tablets allowed to tumble over the wax until the desired sheen is attained. • A third method is light spraying of the tablets with wax dissolved in a nonaqueous solvent. • Two or three coats of wax may be applied, depending upon the desired gloss. 2) Film-coating tablets • The sugarcoating process is tedious, time-consuming, and specialized, requiring the expertise of highly skilled technicians, • It results in coated tablets that may be twice the size and weight of the original uncoated tablets, • Sugarcoated tablets may vary slightly in size from batch to batch and within a batch. • The film-coating process, which places a thin, skin-tight coating of a plasticlike material over the compressed tablet, was developed to produce coated tablets having essentially the same weight, shape, and size as the originally compressed tablet. • The coating is thin enough to reveal any identifying monograms embossed in the tablet during compression by the tablet punches. • Film-coated tablets also are far more resistant to destruction by abrasion than are sugarcoated tablets. • Film-coating solutions may be nonaqueous or aqueous. The nonaqueous solutions contain - A film former - An allowing substance - A plasticizer - A surfactant - Opaquants and colorants • Sweeteners, flavors, and aromas A glossant A volatile solvent or water Tablets are film-coated by application or spraying of the coating solution on the tablets in ordinary coating pans. • The volatility of the solvent enables the film to adhere quickly to the surface of the tablets. A typical aqueous film-coating formulation contains - Film-forming polymer Plasticizer Colorant and opacifier Vehicle 3) Enteric coating • Enteric-coated solid dosage forms are intended to pass through the stomach intact to disintegrate and release their drug content for absorption along the intestines. • Enteric-coating materials may be applied to either whole compressed tablets or to drug particles or granules used in the fabrication of tablets or capsules. 4) Fluid bed or air suspension coating • Fluid bed coating, is spray coating of powders, granules, beads, pellets, or tablets held in suspension by a column of air. • Fluid bed processing equipment is multifunctional and may also be used in preparing tablet granulations. • Both the top-spray and bottom-spray methods may be employed using a modified apparatus used for fluid bed granulation. • A third method, the tangential spray technique, is used in rotary fluid bed coaters. • The three systems are increasingly used for application of aqueous or organic solvent-based polymer film coatings. • The top-spray coating method is particularly recommended for taste masking, enteric release, and barrier films on particles or tablets. • It is most effective when coatings are applied from aqueous solutions, latexes, or hot melts. • The bottom-spray method is recommended for sustained-release and enteric-release products. • The tangential method is used for layering coatings and for sustained-release and enteric-coated products. 5) Compression coating • It is similar to the preparation of multiple compressed tablets having an inner core and an outer shell of drug material, core tablets may be sugarcoated by compression. • The coating material, in the form of a granulation or powder is compressed onto a tablet core of drug with a special tablet press. • Compression coating is an anhydrous operation and thus may be safely employed in the coating of tablets containing a drug that is labile to moisture. 6. Impact of manufacturing changes on solid dosage forms The quality and performance of a solid dosage form may be altered by changes in formulation or by changes in the method of manufacture. - The changes in formulation may arise from the use of starting raw materials the use of different pharmaceutical excipients the use of different quantities of the same excipients in a formulation, the addition of a new excipient to a formulation. - - - The changes in the method of manufacture may be Use of processing or manufacturing equipment of a different design, A change in the steps or order in the process or method of manufacture, Different in-process controls, quality tests, or assay methods, Production of different batch sizes, Employment of different product reprocessing procedures, Employment of a different manufacturing site. 7. Official and commercially available tablets There are hundreds of tablets recognized by the USP and literally thousands of commercially available tablet products from virtually all pharmaceutical manufacturers. 8. Packaging and storing tablets • Tablets are stored in tight containers, in places of low humidity, and protected from extremes in temperature. • Products that are prone to decomposition by moisture generally are packaged with a desiccant packet. • Drugs that are adversely affected by light are packaged in light-resistant containers.
