Match each of the following clinical scenarios with the most accurate corresponding pharmacokinetic alteration expected in that patient.
- A patient with acute decompensated heart failure who is administered an intravenous drug with a high hepatic extraction ratioDecreased systemic clearance secondary to reduced organ perfusion
- A patient with oliguric end-stage renal disease who is prescribed a renally cleared hydrophilic antibioticUnchanged loading dose requirement but decreased maintenance dose requirement
- A patient with severe hypoalbuminemia secondary to nephrotic syndrome who is taking a highly protein-bound drugIncreased apparent volume of distribution and decreased total steady-state plasma concentration
- A patient taking an oral contraceptive pill who is initiated on rifampin therapy for a latent tuberculosis infectionDecreased elimination half-life and decreased steady-state plasma concentration
Answer
The correct matches are: 1) Heart failure matches with decreased systemic clearance due to reduced organ perfusion. 2) End-stage renal disease matches with unchanged loading dose but decreased maintenance dose. 3) Hypoalbuminemia matches with increased apparent volume of distribution and decreased total steady-state concentration. 4) Rifampin therapy matches with decreased elimination half-life and decreased steady-state plasma concentration.
Each clinical scenario alters specific pharmacokinetic parameters. Heart failure reduces hepatic blood flow, impairing clearance of flow-dependent (high-extraction) drugs. Renal failure necessitates reduced maintenance doses due to lower clearance, but loading doses remain unchanged because the volume of distribution is stable. Hypoalbuminemia increases the free fraction of protein-bound drugs, raising the volume of distribution and lowering total steady-state levels due to increased clearance of total drug. Enzyme inducers like rifampin increase clearance, thereby shortening the half-life and lowering steady-state concentrations of substrate drugs.
Step-by-Step Solution
Key Concept
Various disease states and drug interactions predictably alter specific pharmacokinetic parameters such as clearance, volume of distribution, half-life, and required dosing regimens.