Gentamicin Dosing Card (Traditional Therapy)

Louisiana State University Medical Center Shreveport, Louisiana

The following guidelines are applicable to the adult population only.

  1. Before the start of therapy all patients must have a serum creatinine ordered, if they have not had one drawn in the last 24 hours. Thereafter, serum creatinine should be ordered on a daily basis.
  2. Obtain patient height and weight
  1. The dose should be based on the patient's total body weight (TBW) unless the patient is obese (i.e.>20% over ideal body weight).
  2. If the patient's TBW is > 20% above his estimated ideal body weight (IBW), calculate the dosing weight (DW) where:

IBW (MALES)= 50kg + (2.3 X INCHES > 5 FT)

IBW (FEMALES)= 45.5KG + (2.3 X INCHES>5 FT)

DW (KG) = (TBW - IBW) 0.4 + IBW

3. Select loading dose according to site/severity of infection and desired peak levels

Peak Level Site/Severity of Infection Loading dose
4 mcg/mL Uncomplicated lower UTI 1.0-1.5 mg/kg
4-5 mcg/mL Gram (+) endocarditis (synergy w/ pen) 1.5-2.0 mg/kg
6-8 mcg/mL Gram (-) septicemia, wound inf, other serious 2.0-2.5 mg/kg
8-10 mcg/mL Gram (-) pneumonia, life threatening inf. 2.5-3.0mg/kg

 

4. Select maintenance dose (MD) as % of chosen loading dose according to patient's estimated creatinine clearance (CrCl) (usually 90% of LD q8h in normal renal function)

  1. Estimation of CrCl (mL/min)

CrCl males= 140-age/Scr

CrCl females = 140-age X 0.85/Scr

Estimation can be affected by nutritional status, liver disease, ketosis.

Maintenance Dosing Nomogram

CrCl MD(%LD) Dosing Interval
>90 90 8 hours
80 80 8
70 70 8
60 90 12
50 80 12
40 70 12
30 90 24
20 80 24
10 60 24

 

5. Obtain peak and trough concentrations around third dose following initiation or readjustment of therapy at steady-state.

6. Usual recommended therapeutic range (gentmicin/tobramycin)

PEAK= 5-10 mcg/mL TROUGH= <2mcg/mL

7. Rule of Thumb- if the peak concentration is significantly higher or lower than expected, adjust the dose, if trough concentration is significantly higher or lower than expected, adjust the dosing interval.

Once Daily/High Dose Gentamicin Dosing Card

The following guidelines are applicable to the ADULT population only, except those with ascites, burns of >20% of total body surface area, pregnancy, end stage renal disease requiring dialysis, or enterococcal endocarditis.

  1. Before the start of therapy, all patients must have a serum creatinine ordered if they have not had one drawn in the last 24 hours. Thereafter, serum creatinine should be ordered on a daily basis.
  2. Obtain patient height and weight
  1. The dose should be based on the patient's total body weight (TBW) unless the patient is obese(i.e.>20% over ideal body weight).
  2. If the patient's TBW is >20% above his estimated ideal body weight (IBW), calculated the dosing weight (DW) where:

IBW (MALES)= 50KG+(2.3 X INCHES >5FT)

IBW (FEMALES)= 45.5KG + (2.3 X INCHES >5 FT)

DW (KG) = (TBW-IBW)0.4 + IBW

3. Order dose of 7mg/kg (rounded to nearest 20 mg increment) to be administered as an ivpb over 30 minutes.

  1. Order a single random blood sample to be obtained between 6 and 14 hours after the start of the infusion.
  2. Once the levels are reported, use the following nomogram to determine the appropriate dosing regimen. (Note: if a level falls on the line between two dosing intervals, use the longer interval in order to prevent drug accumulation.)
  3. Desirable calculated levels are as follows:

PEAK= 16-23 mcg/mL Trough < 1.0 mcg/mL (preferably 0-0.5mg/l)

4. Once the gentamicin maintenance dose is established a random serum drug level should be repeated:

  1. if a change in Volume of Distribution (Vd) is suspected.
  2. if serum creatinine increases by >0.4 mg/dl.
  3. At least every 3-5 days while on gentamicin therapy.

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