A drug substance is the purified, pharmacologically active material that provides the intended therapeutic effect of a medicine, but does not include intermediates used in the synthesis of such ingredient. It encompasses the active chemical or biological entity in its raw, unformulated form, prior to being combined with excipients to create the final dosage form. Drug substances must meet defined quality, purity, and stability criteria, as these characteristics directly influence the safety and performance of the resulting medicine.
The term drug substance can also be used to refer to a physical mixture of two or more drug substances used to produce a fixed-combination drug product. Drug substances differ from drug products, which are the finished, formulated medicines designed for patient use (e.g., tablets, capsules, injectables) and incorporate the drug substance along with other ingredients that influence delivery, stability, and patient acceptability.
Guidance for Industry #169 – Drug Substance
Chemistry, Manufacturing and Controls: Regulatory Considerations Through Clinical Development
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Drug substance vs. drug product – these are the differences – Single Use Support
Active Pharmaceutical Ingredients (APIs) and Drug Development | Blog | Biosynth