# 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: 57 yr | Gender: female | Weight: 64.5 kg | ht: 69 in |

Scr: 2.23 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 | 300 mg | 1 hr | |

09/18/15 | 1000 | 300 mg | 1 hr | |

09/18/15 | 2200 | 300 mg | 1 hr | |

09/19/15 | 0930 | | | 3.81 mg/L |

09/19/15 | 1000 | 300 mg | 1 hr | |

09/19/15 | 1225 | | | 11.02 mg/L |

09/19/15 | 2150 | | | 4.31 mg/L |

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**Some Equations:**

Equation 27.4.1 IBW for Male Patients

Equation 27.4.2 IBW for Female Patients

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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