Generic drug usually means a drug that has the same qualitative and quantitative composition of the active ingredient and the same pharmaceutical form as the reference branded drug, and whose bioavailability with the reference drug has been demonstrated by an appropriate bioequivalence study [1]. Generic substitution is defined as switching between a branded product and a generic version of the same drug (such as switching from Taxotere® to docetaxel) [2]. Promoting generic substitution from multiple sources into the healthcare system is aimed at maximising population health subject to improve
the overall healthcare delivery systems [3]. This strategy of drug substitution is proven to be effective since it is often easier to intervene on the expenditure of medicines because of their identified cost [4-6]. However, this has been accompanied by a variety of problems of which the most critical is the widespread distribution of substandard generics and fake drug products. As a consequence, health care providers and patients are usually concerned when selecting one drug from among several bioequivalent ones during the treatment regime [7, 8].
Dissolution is an example of in-vitro test which can be used to identify formulations that may present potential bioequivalence problems. It is defined as the amount of substance that goes into solution per unit time under standardised conditions of liquid/solid interface, solvent composition and temperature [9]. It is considered one of the most important tools to predict the in-vivo bioavailability and in some cases replacing clinical studies to determine bioequivalence
[10]. Dissolution is considered as the rate limiting step for a drug to be absorbed from solid dosage form following oral administration. It is the process of transporting the drug substances from the gastrointestinal lumen into the systemic circulation [11]. Absorption is the first step before the distribution, metabolism and elimination (ADME) of drugs in the human body. It usually depends on the stages of disintegration, disaggregation, drug release from the pharmaceutical form, its dissolution under physiological conditions and permeability through the biological membranes, (Figure 1) [12, 13].
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