Question

An adult male (73 years old, 65 kg) with diabetes mellitus is placed on hemodialysis. His residual creatinine clearance is <5mL/min. The patient is given tobramycin, an aminoglycoside antibiotic, at a dose, at a dose of 1 mg/kg by IV bolus injection. Tobramycin is 90% excreted unchanged in the urine, is less than 10% to plasma protein, and has elimination half-life 2.2 hours in patient with normal renal function. In this patient, tobramycin has an elimination t1/2 of 50hours during the interdialysis period and an elimination t1/2 of 8 hours during hemodialysis. The apparent volume of distribution for tobramycin is about 0.33 L/kg. For this patient, calculate the followings:

a. The initial plasma antibiotic concentration after a first dose of tobramycin

b. The plasma drug concentration just before the start of hemodialysis (48 hours after the initial tobramycin dose

c. The plasma drug concentration at the end of 4-hours of hemodialysis

d. The amount of the drug lost from the body after dialysis

e. the tobramycin concentration in the blood after a replenishment dose of 1 mg/kg (immediately and post dialysis)​

Answer 1

THE plasma drug concentration just before the start of hrmodialysis( 48 hours after the initial tobramycin dose)