This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacokinetics, Subject name: Pharmacology
[{'content': 'Which of the following factors is affected by the bioavailability of a drug? \nSelect and explain. \nA. Half life of the drug, B. Volume of distribution, C. Dose of the drug, D. pKa value', 'role': 'user'}, {'content': 'Answer: C \nExplanation: * 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.', 'role': 'assistant'}]