Which of the following factors is affected by the bioavailability of a drug?

* 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.