PHARMACOKINETICS PRACTICE PROBLEMSDENTAL PHARMACOLOGY PL3311) If equal volumes of intestinal juice (pH = 5.4) and plasma (pH = 7.4) were separated by anepithelial membrane, what would be the ratio of concentrations (plasma/intestinal juice) achievedby an organic acid (pKa = 6.4)? An organic base (pKa = 6.4)?2) A 400 mg dose of a drug was given to a 60 kg woman. Extrapolation of the linear portion ofthe drug disposition curve intersects the Y-axis at 30 mg/L. What is the fractional volume ofdistribution?3) The figure shows disposition of a drug after an intravenous dose of 1500 mg. Calculate thefollowing: Volume of distribution (Vd); elimination constant (Ke); half-life (T1/2); clearance (Cl).4) If a drug has an elimination rate constant (Ke) of 0.3 days-1, how much time is required forelimination of 95% of the drug?5) A drug has a half-life of 3.5 hours, and a fractional Vd of 0.6 L/kg. If the drug is administeredby IV infusion to a 65 kg man at a constant rate of 2 mg/min, what will be the steady-stateplasma concentration? How long will it take to reach 95% of that concentration?6) A drug was present in the plasma of a patient at a concentration of 400 µg/ml. 7 hours later,the concentration was 50 µg/ml. Assuming that the drug is eliminated by zero order kinetics,how long did it take to reduce the original concentration by 50%? Assuming that the drug iseliminated by first order kinetics, how long did it take to reduce the original concentration by50%?7) Drugs A and B are alike in that they are not metabolized, not bound to plasma proteins, andnot secreted or reabsorbed by the renal tubule. Their volumes of distribution in a 50 kg womanare 10L and 30L, respectively. If the elimination half-life for A is 60 minutes, what is theelimination half-life for B? (Hint: What can you assume about the clearance of A and B?)8) A drug is administered as an IV bolus dose of 200 mg to an 80 kg patient. The fractionalvolume of distribution is 0.1 L/kg. What is the theoretical concentration of drug in plasma attime = 0? After 4 hours, the concentration of the drug is 15 mg/L What is the total amount ofdrug in the patient’s body at 4 hours?9) 100 mg of drug is given orally every 6 hours to a 70 kg patient. The bioavailable fraction afteroral dosing is 50%. The drug is eliminated by first-order kinetics, with a half-life of 6 hours. The fractional volume of distribution is 0.7 L/kg. How long will it take to achieve a plasmaconcentration that is 95% of the steady-state concentration?10) See question 9, above. If you wished to achieve that steady-state plasma concentrationimmediately by IV bolus injection, what loading dose would you give? If you wished tomaintain that steady-state concentration indefinitely by oral administration, what dosage regimenwould you
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