Active pharmaceutical ingredient process characterization

Characterization starts once the synthetic route has been selected, although there will be opportunities to modify the route if the changes do not impact the final solid state or impurity profile of the final active pharmaceutical ingredient. The primary objective is to understand, through experimentation, the chemical and physical chemical processes involved in the transformation of raw materials to intermediates and products. The primary outcome is a process definition that includes the order of manufacturing steps, process parameter control methodology, process parameter limits, raw material specification, and diagnostic metrics. 

Now I would like to turn to some of the issues of operations within the manufacturing process itself and speak to certain process controls that are expected. In a chemical synthesis sequence, as I mentioned above, intermediates will need to be fully characterized. That characterization will then lead to a set of specifications for the intermediate, that is, its level of purity, its form, etc. Test procedures that demonstrate that the intermediate meets specifications must be established. Some intermediates are deemed to be more important than others and are given specific designation, such as pivotal, key, and final intermediates. In those cases, it is necessary to demonstrate that the specific and appropriate structure is obtained from the chemical reaction and that the yield of the intermediate is documented and meets the expected yield to demonstrate process reproducibility and control. Purity of the substance is to be appropriately documented. And, finally, in reactions which produce pivotal, key, and final intermediates, side products or undesirable impurities are identified and their concentrations measured and reduced by appropriate purification procedures so that the intermediate meets in-process specifications. Thus, those important intermediates become focuses of the process to demonstrate that the process is "under control" and functioning in a reproducible and expected manner. All of these activities ultimately are designed to lead to the production of the actual active ingredient which is referred to then as a "bulk pharmaceutical agent." That final product will need to be completely characterized which then will document that it meets a set of specifications ("Final Product Specifications") for qualification as suitable for pharmaceutical use. 

Moreover, a complete characterization of all the chemical constituents from a natural product is often unknown. Unlike pharmaceuticals, botanical products are complex mixtures in which the active ingredients may be unknown or only partially characterized. For several herbal products, the active ingredient or the quantity necessary for effectiveness has not been determined. For example, some manufacturers standardize St. John s wort according to its hypericin content, which is only 1-10 identified active components in this herb. Additionally, the chanical makeup of a natural product may vary depending on the part of the plant processed (stems, leaves, roots, etc.), seasonality, and growing conditions. ... 

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