Aminoglycoside Clearance Estimate
Info
Gender Male Female
Age in years
Serum Creatinine
unit µmol/L mg/dL
Height
unit Inches cm
Weight
unit lbs kgs
Is patient obese Yes No
R e s u l t s
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AmCl
 
-
 
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Aminoglycoside Clearance Estimate

Elimination of aminoglycosides is almost entirely by renal excretion. Since aminoglycoside clearance corresponds to creatinine clearance over a wide range of renal function, aminoglycoside clearance can be calculated using formulas for estimating creatinine clearance.

The method of Sarrubi and Hull utilizes serum creatinine (Scr), lean body weight (LBW), age, and gender to estimate creatinine clearance. This method considers more patient variables, which may improve the estimation of aminoglycoside elimination.

Aminoglycoside Clearance is clinically useful in determining dosage interval for dosing of aminoglycosides such as gentamicin, amikacin or tobramycin (may also apply for vancomycin).

The formula used aminoglycoside clearance (AmCl):

  • AmCl = (Gender)*((140 - Age) × LBW / (Scr × 72))
  • AmCl = Aminoglycoside clearance in ml/min
  • Gender: Male = 1, Female = 0.85
  • Age = Age in years
  • LBW = Lean body weight
  • Scr = Serum creatinine in mg/dl

Note: This formula is for patients with stable renal function ONLY.

For Lean Body Weight

  • Males: LBW = 50 kg + 2.3 kg for each inch in height over 60 inches.
  • Females: LBW = 45.5 kg + 2.3 kg for each inch in height over 60 inches.

For less than 60 inches LBW is restricted to

  • Males: LBW = 50 kg
  • Females: LBW = 45.5 kg

For obese patient LBW would give wrong estimation hence instead of LBW we use OBW = LBW + 0.4(Weight - LBW)

** In the event that patient is underweight and LBW is > than actual weight, actual weight will be entered into the equation.

Items to be entered:

  • Gender (Male or Female)
  • Age in years
  • Serum creatinine in mg/dl
  • Height in inches
  • Weight in kg
  • Is patient obese(Yes or No)

Note: Height and Weight are used in calculation of LBW. If patient is obese is a yes then we calculate OBW using LBW.

Interpretation:

Determination of dosing interval of Aminoglycoside (once daily dosage) using Aminoglycoside Clearance:

AmCl(ml/min) Interval Monitoring
>=60 Every 24 hours Drug level 8-12 hour after dose.
40-59 Every 36 hours Nomogram recommended to confirm or modify dosage interval.
20-39 Every 48 hours Dosage Levels 1/week during prolonged thearapy.
<20 Adjusted by monitoring levels

Note: For AmCl >=60 ml/min or higher and if duration of therapy is less than 5 days no monitoring is required.

Reference:

  1. Sarubbi FA Jr, Hull JH. Amikacin serum concentrations: prediction of levels and dosage guidelines. Ann Intern Med . 1978 Nov;89:612-8.
  2. Traynor AM, Nafziger AN, Bertino JS Jr. Aminoglycoside dosing weight correction factors for patients of various body sizes. Antimicrob Agents Chemother . 1995 Feb;39(2):545-8.
  3. Pai MP, Nafziger AN, Bertino JS. Simplified Estimation of Aminoglycoside Pharmacokinetics in Underweight and Obese Adult Patients. Antimicrob Agents Chemother . 2011 September; 55(9): 4006-4011.