|
|
|
|
|
|
|
crystalline cellulose, a notable exception to the correlation, exhibits a high elastic recovery but nevertheless binds well. |
|
|
|
|
|
|
|
|
b. Effects on Compression Rate Armstrong and Blundell's study (1985) on rate-dependent deformation effects showed that the strength of tablets made from four directly compressible tablet excipients, Avicel, Emcompress, Fast Flow Lactose, and Starch 1500 (pregelatinized), were dependent on the speed of the rotary tablet press and hence on the rate of tablet compression. In virtually all cases, an increase in the tablet press-speed led to a reduction in tablet strength. |
|
|
|
|
|
|
|
|
In general, tablets made from materials that consolidate by deformation such as Avicel, compressible starch, etc., are improved by increasing the time during which they are exposed to the compression force, i.e., the so-called dwell time. On the contrary, those materials such as lactose, dibasic calcium phosphate, etc., which consolidate by fragmentation, exhibit little dependence on press speed. |
|
|
|
|
|
|
|
|
A rational approach to dosage form design for any drug requires a complete understanding of its physicochemical and biopharmaceutical properties, which can have a tremendous impact on its bioavailability and thereby on its efficacy and toxicity profile. Thus, understanding these parameters is often tantamount to the selection and development of the optimum dosage form. Properties that dictate the selection and formulation of the dosage form include |
|
|
|
|
|
|
|
|
solubility and dissolution rate, |
|
|
|
|
|
|
|
|
partition coefficient (lipid-water), |
|
|
|
|
|
|
|
|
stability and/or degradation in the physiologic fluids, |
|
|
|
|
|
|
|
|
susceptibility to metabolic inactivation, and |
|
|
|
|
|
|
|
|
transport mechanism across biologic membranes. |
|
|
|
|
|
|
|
|
Once the physicochemical and biopharmaceutical properties of the drug are determined and the desired plasma-concentration-time profile is defined, the pharmaceutical scientist can select and develop an efficacious dosage form by employing appropriate excipients. |
|
|
|
|
|
|
|
|
Dissolution testing of pharmaceutical solid dosage forms has emerged as the single most important test that, when carried out appropriately, will ensure the quality of the product. Interest in dissolution standards and their significance has been mounting steadily during the past decade. Knowledge of critical oper- |
|
|
|
|
|