Factors that include particle size and solubility belong to which concept?

• A. Drug standards
• B. Factors affecting bioavailability
• C. Bioassay
• D. United States Pharmacopeia

Answer: (B)

Particle size and solubility influence how well a drug dissolves and is absorbed in the body, which directly affects bioavailability—the fraction of the dose that reaches systemic circulation. Smaller particles provide a larger surface area, speeding dissolution and making absorption more efficient. Solubility determines how much drug can dissolve in the gastrointestinal fluids; if solubility is poor, dissolution becomes the limiting step, restricting absorption even if the drug is permeable. Together, these properties are classic factors that govern bioavailability and explain why they’re grouped under that concept. Drug standards or USP relate to quality specifications, not absorption; a bioassay measures biological activity, not physicochemical dissolution factors.