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  Gentamicin Calculator (Under development)  

Gentamicin Dose Calculator

Age (yrs)
Weight (kg)
Height (cm)

OR

(inches over 5ft)

Use inches over 5ft
  Female patient  
Serum Creatinine (μmol/L)
Creatinine Clearance
(GFR)
(mL/min)
Dose determining weight (Kg)
Gentamicin regimen (mg/Kg)
Gentamicin Dose (mg)

Gentamicin Dosing Interval Calculator

Level (mg/L)
Time (Hours)
Dosing Regimen
Dosing Interval (Hours)


Gentamicin Level Predictor


Age (yrs)
Dose determining Weight (kg)
  Female patient  
Serum Creatinine (μmol/L)
Dosing Regimen
Time, t (Hours)
Dose recieved (mg)
Creatinine Clearance
(GFR)
(mL/min)
Level (at Time t) (mg/L)

Calculation(s) used

Calculation of Gentamicin dose

Dose determining weight
Ideal Body Weight is calculated from the patients height (using IBW calculation), this is compared with the patients actual body weight. If actual weight is > 20% of the IBW, then patient is classified as obese and the adjusted body weight is used as the dose-determining weight otherwise actual body weight is used.

Regime of 3mg/Kg is for Creatinine clearance of >15 mL/min and <30mL/min, 5mg/Kg is used for creatinine clearance greater than 30mL/min.


Prediction of Plasma level

Aminoglycosides are cleared renally and so Cockgroft-Gault prediction of GFR can be used to calculate their clearance in L/h.

Elimination rate constant, k is then calculated using  Clearance and volume of distribution.



Plasma concentration at time C1 can be calculated based on the Elimination rate constant, k at time t1.



where
 S=Salt fraction(=1), F=Bioavailability (=1), Vd = Volume of Distribution (L/Kg)

Notes

Gentamicin should not be used in the following patient groups:

Myasthenia Gravis
Hypersensitvity to aminoglycosides
Severe renal impairment

Once daily dosing should not be used in patients with:

Infective Endocarditis
Major Burns (>20% of body surface area)
Pregnancy

References
1. Winter, M.E., (2004). Basic clinical pharmacokinetics. London: Lippincott, Williams and Williams.
2. Clinical Pharmacokinetics Soraya Dhillon and Andrzej Kotstrzewski

Copyright 2006-2010 Jamie Al-Nasir, all rights reserved