1.4. Tablet Disintegration
For a drug to be absorbed from a solid dosage form after oral administration, it must first be in solution, and the first important step toward this condition is usually the break-up of the tablet; a process known as disintegration 26 . The disintegration test is a measure of the time required under a given set of conditions for a group of tablets to disintegrate into particles which will pass through a 10 mesh screen. Generally, the test is useful as a quality assurance tool for conventional dosage forms. The disintegration test is carried out using the disintegration tester which consists of a basket rack holding 6 plastic tubes, open at the top and bottom, the bottom of the tube is covered by a 10-mesh screen. The basket is immersed in a bath of suitable liquid held at 37 o C, preferably in a 1L beaker. For compressed uncoated tablets, the testing fluid is usually water at 37 o C but some monographs direct that simulated gastric fluid be used. If one or two tablets fail to disintegrate, the test is repeated using 12 tablets. For most uncoated tablets, the BP requires that the tablets disintegrate in 15minutes (although it varies for some uncoated tablets) while for coated tablets, up to 2hours may be required 3 . The individual drug monographs specify the time disintegration must occur to meet the Pharmacopoeial standards.
In the past, the only release index required for a tablet was its disintegration time which does not necessarily measure the physiological availability of the drug in a patient. Studies have shown that the agitation of the gastric contents during normal contractions is quite mild in contrast to the turbulent agitation produced in the disintegration test apparaus 27 . The low order magnitude of agitation in the stomach produces substantially higher disintegration in vivo than those obtained using the USP apparatus. Furthermore, the particles of the disintegrated tablets are not dispersed throughout the stomach but remains as an aggregate. Thus, the tablet disintegration test is limited to manufacturing control of lot-to-lot variations in individual products and is not a measure of bioavailability 27 . Nevertheless, it is used to provide a simple and useful means for monitoring and controlling the quality of tablets.