Direct Compression Method for Tablets PDF

Tablets are solid dosage forms usually prepared with the aid of suitable pharmaceutical excipients. They 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. Most...

Tablets are solid dosage forms usually prepared with the aid of suitable pharmaceutical excipients. They 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. Most tablets are used in the oral administration of drugs ,Many of these are prepared with colorants and coatings of various types.  Other tablets, such as those administered sublingually, buccally, or vaginally, are prepared to have features most applicable to their particular route of administration. 1) Unit dosage forms 2) Good mechanical, chemical and microbiological stability. 3) Could be formulated as coated tablets to mask bad odor or taste. 4) Could be formulated enteric or delayed release to ensure special release profiles. 5) Suitable for large scale production. 6)The easiest and cheapest to package and ship. 7)The lowest in cost (for the patients). 8)Convenient (light to be carried by the patient). 9)Easy administration. 10)Easily identifiable. 1) Some drugs resist compression into dense compact (due to their amorphous) 2) Drugs with poor wetting or slow dissolution properties are difficult or impossible to be formulated as tablet. 3) Bitter testing drugs, drugs with an objectionable odor or drugs that are sensitive to oxygen may require encapsulation or coating. In such cases , the capsule may offer the best and lowest cost approach. 4) Can not be used for children and unconscious patients. Tablet Ingredients : classified according to their principle function they exert in the tablets Tablet ingredient Active Excipent Diluent pharmaceutical Binder ingredients (API) Lubricants Glidant Anti-adherent Disintegrant Other ( adsorbant, dyes,flavor, sweetening agents,… ) 1. API: Active Pharmaceutical Ingredient (medication) 2. Diluent or bulking agent: to increase weight and improve content uniformity (act as fillers). 3. Binder: binds all the powder together to make it as a cohesive paste. 4. Lubricants: reduces friction between the particles and the stickiness of the tablet to the die. 5. Glidant: promotes the flowability of the powder by reducing the friction between molecules. 6. Anti-adherent: provides non-sticking properties 7.Disintegrant or disintegrating agent: helps tablet to break up and dissolve to release the medicament. 8. Other ingredients: dyes, flavors, sweetening agents, adsorbents,and buffers sometimes needed in tablet formulation.  Tablet preparation method compression method Granulation method Direct Wet Dry compression granulation granulation  Direct compression : is a method for preparing tablets. In this process, the API and suitable excipients are mixed to form a uniform powder mixture which is compressed directly into tablets , therefore, direct compression is only applicable to materials possessing good flowability and compressibility. crystalline chemicals have good compressible characteristic and flow properties (because of the creation of certain cohesive bonds between crystals due to the pressure of compression, whereas in amorphous form it will not , materials have relatively weak intermolecular attraction forces or are covered with a film of adsorbed gas that tends to hinder compaction) Crystalline materials such as: Potassium salt (chlorate, chloride, bromide), Sodium chloride, Ammonium chloride, Aspirin in granules form (Asagran) etc. 1. Useful for material affected by moisture (dry process) 2. Low cost (compared with other methods) 3. Low labor input (low workers & machines) 4. Fast (few processing steps are required) 5. Minimal space is needed 1. Used only for intermediate dose medications. 2. All additives should have good flowability & compressibility. 3. There is limited number of materials having crystalline form. 4. It has an extended disintegration time → delayed absorption 5. Differences in particles' sizes (when we have more than one type of ingredients) → segregation → content uniformity problems. 6. Because the process is carried in dry condition, static charges may exit & result in mixing problems (hindrance of flowability). 7. Possible reaction of the excipient with the drug (incompatibility). For example: the reaction of spray dried lactose with amine salts resulting in darkening of the color with aging.  Large tablets could be formulated from large doses drugs but they are difficult to swallow and not accepted by patients.Therefore, most large doses of drugs are not preferably prepared by this technique Moreover, drugs having small doses (like digoxin) can not be compressed directly because a uniformed distribution of the drug in the tablets could not be maintained. Hence, this method is usually used for moderate doses only. We can use direct compression when we have a drug with poor compressibility by adding a diluent having good compressibility (70% diluent & 30% drug) but this is not an ideal technique. Ideally: all the ingredients should have good compressibility.  For tablets manufacture, fine powders are the basis of most formula.But they don’t flow easily and are difficult to feed into the die and they don’t bind easily under compression. Therefore, particles are sometimes converted into granules before compression. Granulation : is the process the fine powders are converted to granules using either wet granulation or dry granulation that improve flowability of the powder to ensure a uniform fill of the die cavity and good compressibility. 1-Die filling : accomplished by gravitational flow of powder from a hopper via the die table into the die. The die is closed at its lower end by lower punch. 2-Tablet formation : the upper punch descends and enter the die and the powder is compressed until a tablet is formed. During the compression phase, the lower punch can be stationary or can move upwards in the die. After the maximum applied force is reached, the upper punch leaves the powder. 3-Tablet ejection: During this phase the lower punch rises until its tip reaches the level of the top of the die. The tablet is subsequently removed from the die table by a pushing device. Drug , Filler, Disintegrant, Lubricant, Glidant Blending Compression  Aspirin or acetylsalicylic acid is perhaps the most commonly used analgesic and antipyretic medication. Acetylsalicylic acid appears as odorless white crystals or crystalline powder with a slightly bitter taste. substance role of substance wieght Aspirin API 300 mg Maize starch Binder , Disintegrant 40 mg microcrystalline cellulose Diluent 60 mg talc Lubricant 4 mg prepare 10 tablets  1- weight all ingredients and mix them (except lubricant ) in a bottle for 5 minutes 2- Add lubricant and mix for 1 minutes then compress H.W. / Lubricant is added at last step why ?