PHA 5127
Key to Case study III
(Fall 2003)
Case #1:
A 36 year old female patient was admitted into hospital because of gram-positive bacteria
infection. She is 66 inches tall with weight of 70 Kg. The physician decided to give her
gentamicin via i.v. bolus injection. Before staring the antibiotics, the physician ordered a
lab test for creatinine. The serum creatinine level of this patient was reported to be 1.6
mg/dL. (Ke for aminoglycoside, Ke = 0.00293 (CrCL) +0.014), Unit for Ke is (hr. โ1),
Unit for CrCL is ml/min)
1.) Please calculate what is the creatinine clearance for this patient.
2.) Please state the reason why you need to use IBW for calculate the creatinine
clearance?
3.) Two hours after given a iv. Bolus injection, the blood sample was taken from the
patient, and drug concentration was measured as: 4.2 mg/L. How long will it take for
plasma level drops down to 1 mg/L?
Answer:
1.) Firstly, calculate the IBW, please note this is a case for female patient,
IBW (female) = 45.5 kg + 2.3 * (66-60) = 59.3 (Kg)
Then, by using the IBW, we can calculate the creatinine clearance for this patient.
Or using the equation from equation sheet,
min)/(5.45
6.172
3.59)36140(
85.0 mlCrCL female =
โ
โ
โ
โ
=
min)/(5.45
6.185
3.59)36140( mlCrCL female =
โ
โ
โ
=
2.) Since creatinine is produced by the muscle in the body. And it is not deposit in fat.
3.) Firstly, we need to find out what the Ke value of gentamicin is for this patient.
Ke = 0.00293*45.5 + 0.014 = 0.14 ( hr. โ1)
Recall, for a single dose iv. Bolus,
1*2.4* *14.0*
0=== โโ ttKe
teeCC
T = 10.25 (hr.)
