Coating dissolution test

M Aikman, L Augsburger, I Berry et al. Collaborative development of two-tiered dissolution testing for gelatin capsules and gelatin-coated tablets using enzyme-containing media. Pharmacop Forum 24(5) 7045-7050, 1998. 

Over the years, dissolution testing has expanded beyond ordinary tablets and capsules—first to extended-release and delayed-release (enteric-coated) articles, then to transder-mals, multivitamin and minerals products, and to Class Monographs for non-prescription drug combinations. (Note at the time, sustained-release products were being tested, unofficially, in the NF Rotating Bottle apparatus). 

For some products, e.g., propanolol extended release formulations (USP 27), a modification of the standard method for enteric-coated dosage forms have been introduced to reflect the change from conditions in the stomach to those in the small intestine. This is a step in the right direction, but to achieve dissolution testing that can differentiate between formulations which are robust and those which are not, and especially to be able to predict food effects on the release from... 

Spherical pellets containing 5% triamcinolone acetonide were prepared by Villar-Lopez and co-workers [59] by extrusion/spheronization following formulation with microcrystalline cellulose and/or a hydrophilic excipient like lactose, sodium earbox-ymethylcellulose, or P-cyclodextrin. Their suitability for coating, with a view toward colonic drug deliveiy, was assessed in terms of their size, sphericity, and dissolution test response. The best results were afforded by a 5 90 5 composition of microcrystalline cellulose, P-cyclodextrin, and triamcinolone acetonide, prepared by complex-ation of triamcinolone acetonide with P-cyclodextrin prior to the addition of microcrystalline cellulose. 

Dissolution testing should be carried out in USP Apparams 1 at 100 rpm or Apparatus 11 at 50 rpm using 900 ml of the following dissolution media (1) 0.1 N HCl or Simulated Gastric Fluid USP without enzymes (2) a pH 4.5 buffer and (3) a pH 6.8 buffer or Simulated Intestinal Fluid USP without enzymes. For capsules and tablets with gelatin coating. Simulated Gastric and Intestinal Fluids USP (with enzymes) can be used. 

The relative bioavailability of different enteric diclofenac products was investigated with normal and artificially decreased gastric acidity [63], Only one generic product was found to be fully bioequivalent. Comparison with in vitro studies concluded that the general test on enteric-coated tablets according to Ph.Eur. did not detect any difference between the four products. A modified dissolution test without mechanical stress gave an indication on differences in the lag time of the different products. 

Typically, coatings (e.g., enteric coatings) are intended to delay the release of medication until the dosage form has passed through the acidic medium of the stomach. In vivo tests for delayed-release drug products are similar to those for extended-release drug products. In vitro dissolution tests for these products should document that they are stable under acidic conditions and that they release the drug only in a neutral medium (e.g., pH 6.8). 

A 10.5.1.9 During the full transformation/dissolution tests, agitation should be used which is sufficient to maintain the flow of aqueous medium over the test substance while maintaining the integrity of the surface of the test substance and of any solid reaction product coatings formed during the test. For 1 / of aqueous medium, this may be accomplished by the use of ... 

Table 3 gives a summary of the known dissolution problems with sugar-coated tablets. The progressive decrease in disintegration and dissolution has been ascribed to adherence of gelatin subcoat to the tablet core. This was also a conclusion made in a study where most of the core tablets were found to be dry even at the end of the dissolution test. " Fig. 9 shows an example of sugar-coated chloroquine phosphate tablets exposed to 40°C and 75% RH. Clearly, the dissolution rate decreases with time. ... 

Fee JV, Grant DJW, Newton JM. The effect of surface coatings on the dissolution rate of a non-disintegrating solid (potassium chloride). J Pharm Pharmacol 1973 25 (SuppL) 149P-150P. Thomas WH. Measurement of dissolution rates of potassium chloride from various slow release potassium chloride tablets using a specific ion electrode. J Pharm Pharmacol 1973 25 27-34. Cartwright AC, Shah C. An in vitro dissolution test for slow release potassium chloride tablets. J Pharm Pharmacol 1977 29 367-369. 

In-vitro laboratory testing is important for the development of controlled-release systems. In-vitro protection of the coated amino-acids was evaluated by measuring the amount of methionine or lysine released from the particles at 40°C in a phosphate buffer at pH 6. In-vitro release behavior was determined by dissolution test at 40° C in a buffer at pH 2. 

Y. Insemi and S. Mori, Dissolution tests of commercial tablets containing potassium Influences of humidity on release of potassium salts from coated tablets [in Japanese], Yukuzuiguku 41, 177-183(1981). 

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