A 45-year-old man with chronic renal failure is prescribed a drug that is eliminated exclusively by glomerular filtration. If his glomerular filtrati…

The maintenance dose is directly proportional to the clearance of the drug. Since the drug is eliminated exclusively by the kidneys and GFR is reduced to 25% of normal, renal clearance is reduced to 25%. To maintain the same steady-state plasma concentration ($C_{ss} = \frac{\text{Maintenance Rate}}{\text{Clearance}}$), the maintenance dose rate must also be reduced to 25% of the normal value.