JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD Pharm. D V Year CLINICAL RESEARCH Previous Question Paper (October - 2019 - R08)

Drug characterization involves the systematic identification and analysis of the physical, chemical, and biological properties of a drug candidate. This process is essential to ensure the safety, efficacy, and stability of the compound before it proceeds to clinical trials.

Key aspects include:

• Physicochemical Properties: Determination of molecular weight, solubility, pKa, partition coefficient (logP), and melting point. These properties dictate the drug's absorption, distribution, metabolism, and excretion (ADME) profile.
• Structural Elucidation: Use of analytical techniques such as Nuclear Magnetic Resonance (NMR) spectroscopy, Mass Spectrometry (MS), Infrared (IR) spectroscopy, and X-ray crystallography to confirm the chemical structure and purity of the molecule.
• Stability Testing: Assessing the drug's degradation pathways under various stress conditions (temperature, humidity, light, and pH) to determine its shelf life and storage requirements.
• Biological Characterization: Evaluation of the drug's affinity and selectivity for its biological target through binding assays and functional screens to confirm the mechanism of action.

The dosage form is the physical manifestation of the drug product, designed to deliver the active pharmaceutical ingredient (API) to the site of action in a safe, stable, and effective manner. The selection of an appropriate dosage form is a critical step in drug development.

Key considerations include:

• Route of Administration: The choice between oral (tablets, capsules, syrups), parenteral (injections), topical (creams, ointments), or inhalation forms depends on the drug's physicochemical properties and the desired therapeutic effect.
• Bioavailability Enhancement: Formulation strategies such as solid dispersions, micronization, or the use of surfactants are employed to improve the solubility and dissolution rate of poorly water-soluble drugs.
• Controlled Release Systems: Advanced dosage forms, such as sustained-release or targeted-delivery systems, are designed to maintain therapeutic plasma concentrations over an extended period, reducing dosing frequency and minimizing side effects.
• Excipient Compatibility: Selection of inert substances (binders, fillers, disintegrants, preservatives) that do not interact negatively with the API, ensuring chemical stability and optimal release characteristics.