Aminoglycoside Pharmacokinetics and Pharmacodynamics

Non Steady State Dosing

Questions provided by Michele Splinter, Pharm.D.

You are asked to revise dosing tobramycin therapy in a pulmonary patient who has pneumonia secondary to Klebsiella pneumoniae. The patient is also receiving ceftazidime 2 g every 8 hours.

**Patient characteristics**
Age: 56 yr	Gender: female	Weight: 45 kg	ht: 66 in
Scr: 1.78 mg/dL	Organism MIC 0.5 mg/L

Based on the following doses and serum concentrations, calculate the following: kel, t_1/2, Vd, CL, infusion dose (down to the nearest 10 mg) over 1 hr, dosing interval (up to the nearest 12 hr), projected Cp_max^ss and Cp_min^ss with target Cp_max^ss = 8 mg/L and Cp_min^ss = less than 1 mg/L.

The Data
Date Time Dosage Infusion Duration Serum Concentration

09/17/15 2200 120 mg 1 hr

09/18/15 1000 120 mg 1 hr

09/18/15 2200 120 mg 1 hr

09/19/15 0935 3.78 mg/L

09/19/15 1000 120 mg 1 hr

09/19/15 1205 9.92 mg/L

09/19/15 2130 4.14 mg/L

**The Data**
Date	Time	Dosage	Infusion Duration	Serum Concentration
09/17/15	2200	120 mg	1 hr
09/18/15	1000	120 mg	1 hr
09/18/15	2200	120 mg	1 hr
09/19/15	0935			3.78 mg/L
09/19/15	1000	120 mg	1 hr
09/19/15	1205			9.92 mg/L
09/19/15	2130			4.14 mg/L

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Some Equations:

Equation 27.4.1 IBW for Male Patients

Equation 27.4.2 IBW for Female Patients

Creatine Clearance C-G Equation
Equation 27.4.3 Creatinine Clearance (Cockcroft-Gault Equation)

Equation 27.4.4 Apparent Volume of Distribution, Vd

Equation 27.4.5 Dosing Interval, τ

Equation 27.4.6 Loading Dose

Equation 27.4.7 Maintenance Dose

Last update: Mon 26 Jun 2017 08:28:30 pm

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