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PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

Frequently asked questions

❖ A single IV dose of an antibiotic was given to a 50-kg woman at a dose level of 20
mg/kg. Urine and blood samples were removed periodically and assayed for the parent
drug. The following data were obtained:

✓ What are the half-life (t½) and elimination rate
constant (k) for this antibiotic?

ANSWER

 Using the rate of urinary excretion method

Note,
t* = midpoint of collection period and
t = time interval for collection of urine
samples.
Construct a graph on a semilogarithmic
scale of Du/t versus t*.

t1/2 = 1.0 hr

–1
k = 0.693 h

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