A Comparative Study of Current Superdisintegrants

Oct 01, 2006



Despite a rising interest in controlled-release drug delivery systems, the most common tablets are those intended to be swallowed whole, disintegrating and releasing their medicaments rapidly in the gastrointestinal tract. A disintegrant is a substance in a tablet formulation that enables the tablet to break up into smaller fragments upon contact with gastrointestinal fluids. Such a rapid rupture of the tablet matrix increases the surface area of the tablet particles, thereby increasing the rate of absorption of the active ingredient and producing the desired therapeutic action (1).

The proper choice of disintegrant and its consistency of performance are critical to formulation development of such tablets. In the past, starch was one of the most widely used, inexpensive, and effective tablet disintegrants. A high concentration of starch is required to bring about effective disintegration. Scientists' search for disintegrating agents with efficient disintegrating properties at relatively low concentrations has led to the development of some new compounds with excellent disintegrating properties.

Superdisintegrants generally are used at a low level in the solid dosage form, typically 1–10% by weight relative to the total weight of the dosage unit. Examples of superdisintegrants are crosscarmelose, crospovidone, and sodium starch glycolate, which are a crosslinked cellulose, crosslinked polymer, and a crosslinked starch, respectively. BASF is one manufacturer of crospovidone under the trade name of insoluble "Kollidon" grades. Another manufacturer is ISP's "Polyplasdone XL" grade. Crosscarmelose is marketed mainly as the brand name of "Ac-Di-Sol" by FMC BioPolymer and sodium starch glycolate as "Primojel" from DMV International.

Insoluble grades of Kollidon (crospovidone) are manufactured by a polymerization process that yields crosslinked insoluble polyvinyl-pyrrolidone in the form of a "popcorn" polymer. The polymerization is performed using an aqueous system. No organic solvents are involved at any stage. The crosslinking is of chemical and physical nature, which is mainly achieved by the entanglement of the polymer chains and dominates the product's properties.

Unlike povidone, crospovidone is completely insoluble in solvents and the corresponding products cannot be named according to a K-value or a molecular weight. The product differentiation is conducted mainly by the particle-size distribution. The bulk density and swelling behavior also play an important role in disintegration behavior (2). (BASF supplies the following insoluble grades of Kollidon: Kollidon CL, Kollidon CL-F, Kollidon CL-SF, and Kollidon CL-M, which all comply with current monographs in the European, Japanese, and US pharmacopeias.)

Physical characteristics

Insoluble Kollidon grades are supplied as fine, white, and almost-white powders. They have a slight characteristic odor and are practically tasteless. They are insoluble in all usual solvents.


Table I: Characteristics of various disintegrants.
Bulk and tapped densities of Polyplasdone XL are lower than those of Kollidon CL, perhaps because of the porous structure of Polyplasdone XL or the smoother surface area of Kollidon CL. In consequence of the smaller particle size, bulk densities of Kollidon CL-F and Kollidon CL-SF are lower than the bulk density of Polyplasdone XL grades. Because of its smooth particle surface, Primojel had the highest bulk and tapped densities of all disintegrants. The density of Ac-Di-Sol is between those of Kollidon CL and Primojel (3) (see Table I).

The average particle sizes of Kollidon CL-F and Kollidon CL-SF are significantly lower than those of Kollidon CL and Polyplasdone XL. Kollidon CL-M has the lowest particle size. Polyplasdone XL-10 exhibits a similar particle size as Kollidon CL-F. Ac-Di-Sol and Primojel are significantly finer than Kollidon CL and Polyplasdone XL but coarser than the other disintegrants (Particle size was measured on a "Mastersizer," Malvern Instruments) (3) (see Table I).