Capsules

• Capsules are solid dosage forms in which medicinal agents and/or inert substances are enclosed within a shell of gelatin.
• Content uniformity refers to the determination of homogeneity of distribution of drugs active ingredient the amount of active ingredient, determined by assay, is within the range of 85% to 115% of the label claim for 9 of 10 dosage units assayed, with no unit outside the range of 70% to 125% of the label claim.
• Advantages of capsules include tastelessness, ease of administration, ease of filling either extemporaneously or in commercial scale, permitting the physician to prescribe the exact medication needed by the patient, eliminating the presence of numerous additives, and being the preferred method for administering new therapeutics for evaluation in initial clinical trials.
• Hard gelatin capsules, also known as "Dry-Filled Capsules", are made from a mixture of gelatin, sugar and water.
• Gelatin is a product of the partial hydrolysis of collagen obtained from the skin, white connective tissue and bones of animals.
• Hard gelatin capsules are stable in air when dry but subject to microbial decomposition when moistened.
• Hard gelatin capsules can be colored or left colorless, and can be clear or opaque.
• Hard gelatin capsules contain 13-16% moisture and should be stored in an environment free from excess humidity or dryness.
• Desiccants are used to provide protection from atmospheric moisture.
• Examples of desiccants include dried silica gel, clay or activated carbon.
• The goal in preparing filled hard gelatin capsules is to produce a capsule with accurate dosage, good bioavailability, ease of filling and production, stability and elegance.
• Added substances in hard gelatin capsules should be harmless in quantities used, do not exceed the minimum amount required to provide their intended effect, do not impair the products bioavailability, therapeutic efficacy and safety, and do not interfere with requisite compendial requirements.
• Examples of added substances in hard gelatin capsules include lactose, microcrystalline cellulose, starch.
• A diluent or filler in hard gelatin capsules is used to produce proper capsule fill, examples include lactose, microcrystalline cellulose, starch.
• A binder in hard gelatin capsules provides powder cohesion, examples include lactose, microcrystalline cellulose, starch.
• A disintegrant in hard gelatin capsules assists break-up and distribution of the capsule contents in the stomach, examples include pregelatinized starch, croscarmellose, sodium starch glycollate.
• The basket is placed in a vessel kept at a constant temperature during the dissolution test.
• Soft gelatin capsules are also subjected to a weight variation test where the gross weight of 10 intact capsules is determined individually, each capsule is cut open, and the contents are removed by washing with a suitable solvent, and the solvent is allowed to evaporate at room temperature over about 30 minutes, with precautions to avoid uptake or loss of moisture.
• Compendial requirement for capsules includes disintegration test, dissolution test, and uniformity of dosage units.
• Cleaning and polishing capsules are done using clean gauze or cloth and a vacuum.
• The capsule is placed in a stainless steel cylindrical mesh basket during the dissolution test.
• Soft gelatin capsules are used to hermetically seal and encapsulate liquids, suspensions, pasty materials, dry powders and even preformed tablets.
• Soft gelatin capsules, also known as “Soft-Elastic Capsules”, are made of elastic gelatin, sugar and water, contain more moisture, contain a preservative to retard microbial growth, come in a variety of shapes: oblong, oval and round, and can be single color or two-color tone, clear or opaque.
• The individual shells are weighed and the net contents calculated during the weight variation test.
• Dissolution test refers to the length of time by which 50%-90% of the capsules active ingredient has dissolved in the media of 0.1N HCl, buffer or water at 37C.
• Disintegration test involves placing the capsules in the basket rack assembly, which is immersed 30 times per minute into a thermostatically controlled fluid at 37°C and observed over the time described in the individual monograph.
• The basket is rotated at a constant speed (between 25 and 150 revolutions per minute) during the dissolution test.
• A lubricant or glidant in hard gelatin capsules enhances flow properties of powders, examples include fumed silicon dioxide, magnesium stearate, calcium stearate, stearic acid, talc.
• Uniformity of dosage units may be demonstrated by determining weight variation and/ or content uniformity.
• Weight variation test involves weighing 1.10 capsules individually and determining the content of the active ingredient in each of the capsules.
• Samples are withdrawn for analysis from the same position each time during the dissolution test.
• Applications of soft gelatin capsules include water immiscible volatile and non volatile liquids such as vegetable and aromatic oils, aromatic and aliphatic hydrocarbons, chlorinated hydrocarbons, ethers and esters, alcohols, organic acids, and water-miscible non volatile liquids like polyethylene glycols and nonionic surfactants.
• The goal in filling hard gelatin capsules is to use the punch method.
• Capsule sealing methods include sealing with a colored band of gelatin, heat welding process, thermal coupling, and extemporaneous coating of warm gelatin to the inner surface of the cap.