Dissolution solid drugs

P Singh, S Desai, D Flanagan, A Simonelli, W Higuchi. Mechanistic study of the influence of micelle solubilization and hydrodynamic factors on the dissolution rate of solid drugs. J Pharm Sci 57 959, 1968. 

Equations (25) and (26) show that the dissolution number will also influence the drug absorption in addition to the absorption and dose numbers. Assuming that the initial amount of drug in solution is insignificant compared to the amount of solid drug, the fraction of dose absorbed can be estimated by... 

In vitro dissolution testing is an important tool in the development of solid drug products, as well as in batch quality controls. The aim of the test is to see that the drug is appropriately dissolved in the gastrointestinal tract and made available for absorption. It is therefore highly desirable that the in vitro tests provide data that correlate to the in vivo situation. However, attainment of IVIVC has often failed-and the concept of IVIVC has been challenged. 

Evaluation of the dissolution rates of solid drugs is extremely important in the development, formulation, and quality control of solid pharmaceuticals. The... 

Since the rate of absorption of many drugs from the gastrointestinal tract is controlled by their dissolution rate, this becomes the rate-limiting step. Accurate and reliable measurements of dissolution rate are therefore required in the pharmaceutical sciences. The measurement and interpretation of the dissolution rates of solid drugs in the pure state or from formulations, such as tablets, capsules, and suppositories, has an extensive pharmaceutical literature [95-100]. Moreover, the design, operation, and interpretation of dissolution rate measurements on pharmaceutical solids have been the subject of considerable scientific study, technical development, and debate. 

The dissolution of a solid drug can be described by a modified Noyes-Whitney... 

Type of solution (aqueous vs. lipid) Rate of dissolution of solid drugs Concentrations of a drug present Blood flow to the site of absorption Surface area of absorption... 

For dissolution of solid particles, the Hixson-Crowell cube-root law (Eq. 5.3) assumes that the thickness of the diffusion layer h is constant during dissolution. However, this is not necessarily true. In addition, most drug particles are nonspherical and nonuniform in size. Therefore, very often the dissolution mechanism of solid drug particles is actually much more complicated. Nevertheless, the Hixson-Crowell cube-root law provides the first approximation to model powder dissolution. 

NOTE The values in this table suggest that dissolution rate (or release rate) can be modified significantly by the solubility and particle size of solid drug particles. 

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