By Jim Huang, PhD, Founder & CEO, Ascendia Pharmaceuticals
Injectable solutions are intended for administration to the human body by intravenous, intramuscular, or subcutaneous injection. Advantages of injectables include fast onset, and other parent routes of administration, reproducible PK/efficacy profile, high bioavailability as a result of bypassing the oral absorption barrier, and suitability of administration under hospital setting. In order to meet the safety, efficacy, and quality standards of parenteral dosage forms, injectable solutions have to be sterile, low pyrogen, and meet the requirements of compendia specifications, such as >90% label claim, related substance level lower than the tox qualified level, content uniformity, pH, osmolality, particulate matter, essentially free of visual foreign matter, etc.
The main challenges of parenteral dosage forms are achievement of formulation stability, compatibility of drug substance with packaging components, and sufficient drug concentration within a reasonable pH range and without using excipient levels that causes blood incompatibility and tissue irritation issues. Those requirements necessitate a comprehensive characterization of drug substance physiochemically. In addition, the critical manufacturing processing conditions of injectable liquids have to be evaluated and stringently controlled in order to meet requirements for assay/related substance, CU, leachable/extractables, sterility, pyrogen, and particulate matter specifications.