For a drug to show maximum availability in the body it must be in solution form. So as a first step, the tablets that we take in, should break down to smaller particles or granules.This breaking up process is known as disintegration.
The time taken for disintegration is an important parameter of the tablet. It is determined with an apparatus described in the USP/NF (1). History: In early days a single basket with six open end tubes were designed and later with advent of technology a computerized and atomized two basket apparatus were evolved which is now under use.
Types of disintegration apparatus:
Disintegration apparatus for solid dosage forms ( Tablets, capsules etc) and Disintegration apparatus for semisolid dosage forms ( Suppositories and pessaries ) The USP device to test for disintegration time consists of six glass tubes each of three inches length, open at the top,and held against a 10 mesh screen at the bottom end of the basket rack assembly. To test for the disintegration time, a single tablet is placed in each tube, and the basket rack is positioned in a 1-L beaker containing water or simulated gastric fluid, or stimulated intestinal fluid.
The temperature of the system is maintained at 37+/-2oc and the tablets remain 2.5 cm below the surface of the liquid on their upward movement and descend not closer than 2.5 cm from the bottom of the beaker.
A standard motor-driven device is used to move the basket assembly containing the tablets up and down through a distance of 5 to 6 cm at a frequency of 28 to 32 cycles per minute. Perforated plastic discs may also be used in the test. These discs are placed on top of the tablets. The discs are useful for preventing the tablets from coming out of the assembly. If the tablets are to be declared as USP compliant, they must disintegrate and all particles must pass through the 10-mesh screen in the specified time. Most of the tablets have a maximum disintegration time of 30 minutes, but uncoated tablets have disintegration times as low as 5 min .
As per IP (3): Apparatus for Tablets and Capsules:
It consists of a basket-rack assembly, a beaker (1 liter capacity), a thermostat arrangement (for heating the fluid), a mechanical device (raising and lowering the basket), and immersion fluid.
Basket- rack assembly:
?It consists of six cylindrical glass tubes (length: 77.5+/- 2.5 mm, internal diameter: 21.5 mm, wall thickness: 2 mm).
?The tubes are held in position by two superimposed transparent plastic plates, perforated by six holes having the same diameters as the tubes. (Diameter: 90+/-2 mm thickness: 6.75+/- 1.75)
?To the underside of the lower plastic plate is a woven stainless steel wire cloth with a plain square weave with 2.0+/- 0.2 mm mesh apparatus and with a diameter of 0.165 +/- 0.045mm.
?The upper plate is covered with a six holed stainless steel disc, each about 24+/- 2 mm in diameter, which fits over the tubes and holds them between the plastic plates.
?The plates are held in position and 77.5 mm apart by vertical metal rods at the periphery and also one fixed at the center of the upper plate making sure that the assembly is to be attached to the device for raising and lowering it smoothly at a constant frequency rate of 28-32 cycles/ min through a distance of 50-60 mm. Discs:
?A cylindrical disc made of transparent plastic is provided for each tube, (Diameter: 20.7+/- 0.15 mm; thickness: 9.5+/- 0.15; relative density: 1.18- 1.20).
?In each disc there are five holes (each with a diameter of 2mm) one in the centre and four surrounded equidistantly on a circle of radius 6 mm from the centre are provided.
?Four equally shaped grooves are cut in the lateral surface of the disc they are 9.5 mm wide and 2.25mm deep at the lower surface 1.6mm square.
?The assembly is to be suspended in a 1 lit beaker.
?The volume of the liquid is such that the wire mesh at its highest point is atleast 25mm below the surface of the liquid, and its lowest point is atleast 25 mm above the bottom of the beaker; one must make sure that the top of the basket rack assembly shouldn't be submerged. Heating Device: > There is a thermostat arrangement for heating the liquid and maintaining the temperature at 37+- 2 * c.
Apparatus for Pessaries and Suppositories:
?A transparent sleeve made of glass or plastic. (Height: 60mm, Internal Diameter: 52 mm; appropriate wall thickness).
?A metal device consisting of two stainless discs; each of which contains 39 holes, each 4 mm in diameter.
?The discs are separated by a distance of 30 mm.
?The metal device is attached to the outer sleeve by means of three equally shaped hooks; also the diameter of disc is closely similar to the internal diameter of the sleeve. The difference between IP/BP/USP for this apparatus is only regard to the specification of measurements.
1.The United States Pharmacopeia XX/National Formulary XV. U.S. Pharmacopeial Convention. Rock Ville, MD,1980, pp.958,990.
2.The theory and practice of Industrial Pharmacy by Leon Lachman and Herbert A. Lieberman. Page no: 301.
3. Indian Pharmacopeia, 2007, Volume 1, Published by The Indian Pharmacopeia Commission, Ghaziabad; Disintegration Tests 2.5.1
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