What is a Generic Product?
A generic product is defined as “a drug product that is comparable to branded innovator product in dosage form, strength, route of administration, quality and performance characteristics and intended use”. As per the description given in USFDA, a generic product is pharmaceutical equivalent and bioequivalent to the innovator product. A generic product in simple terms is a duplicate of the innovator product.
Is there a need for Preformulation studies for generic products?
As discussed earlier, pre-formulation studies can be broadly classified into fundamental, derived and compatibility studies. Assuming that innovator and generic product are being developed using same solid form, fundamental pre-formulation properties like aqueous solubility, pKa, log P / log D, pH-solubility profile, intestinal permeability, stability and solid state properties, are expected to be similar. However, derived properties like bulk density, flow and compactability may differ. However, some of these studies may have to be repeated in case of the solid form used by the innovator and generic products are different.
The most important pre-formulation study for a generic product is the compatibility studies. From a formulation development perspective a generic product may either be qualitatively similar or different from the innovator product. This fact governs the quantum of compatibility studies required during development of generic product. Let us first consider us situation where generic product is qualitatively similar to innovator product. Qualitative similarity means that both innovator and generic product have similar excipients. Theoretically, there should not be a need for compatibility studies as presence of the same excipients in innovator product testifies compatibility of API with those excipients. However, despite qualitative similarity a need for compatibility studies could arise, because of differences in (i) solid state properties of API, (ii) impurity profile of the API and (iii) source / vendor of excipients. Understandably the protocol for pre-formulation studies, in such cases, could be less vigorous. The second situation is when excipients in innovator and generic formulation differ qualitatively. This would call for a more rigorous compatibility studies as some of the excipients have not been used earlier with that API.
Solid State Properties during Generic Product Development
There is an increasing understanding that solid state material properties can have a significant impact on performance of the API. This is especially important for BCS class II and IV drugs. Particle properties like size, surface area and free energy can affect dissolution kinetics and subsequent bioavailability. A thorough understanding of these material properties is thus essential to understand stability and performance of the drug product. Hence study of material properties would be an important component of the pre-formulation studies of generic product.
Many pre-formulation studies should be performed, though generic product can be considered a duplicate of the innovator product. Differences in the material properties of the API and excipients, used by innovator and generic manufacturer, can significantly affect performance of the dosage form. Thus it is important to perform preformulation studies for generic products, to identify critical performance attributes.
Dr. Arvind Bansal
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