<prompt> Which of the following factors is affected by the bioavailability of a drug?Half life of the drugVolume of distributionDose of the drugpKa value  <response>: Bioavailability - Fraction of dose reaching the systemic circulation. - Determines the dose High bioavailability - low dose Low bioavailability - high dose Factors affecting bioavailability 1. Absorption More absorption , more bioavailability 2. First pass metabolism More first pass metabolism, less bioavailability Half Life Vd amount of drug plasma concentration Both factors Half life and Vd are not related to bioavailability pKa is the pH of the medium at which 50 of the drug can cross the membrane and 50 cannot cross the membrane. 