Aminoglycoside Dosing

 

● LDEI: large dose, extended interval (dosing)

● SDSI: small dose, short interval (dosing)

● Volume of Distribution

  -v = 0.3L/kg

  -Emaciated (very thin) patients: V = 0.35L/kg

  -Severely ill or trauma patients: V = 0.4L/kg

● Weight to use during dosing1

Weight Description

TBW/IBW

Weight to be used

Normal Body Weight

0.9-<1.2

TBW

Overweight (Obese)

≥ 1.2

Adj. BW

Underweight

> 0.75 - < 0.9

IBW

Emaciated

≤ 0.75

TBW * 1.13

TBW = Total body weight

IBW = Ideal body weight

Adj. BW = Adjusted body weight

Other equations can be found at by clicking here.

 

SDSI (dosing calculator)

● Loading doses are used in SDSI (to give a higher first dose peak)

● Standard loading dose in SDSI (adults): 2mg/kg, then approximately 1.5mg/kg q8. This of course is adjusted based on pharmacokinetics of the individual patient.

● Peak concentrations should be drawn 30 minutes after a 30 minute infusion, immediately after a 1 hour infusion or 60-90 minutes after an IM injection.

 

 

LDEI (dosing calculator)

● LDEI dosing is NOT recommended for patients who are pregnant, in renal failure, osteomyelitits, meningitis, endocarditis, extensive burns, and possible cystic fibrosis

● Loading doses are not given in LDEI because drug concentrations should be at or close to zero before the next dose is given.

Gentamicin/Tobramicin dosing: 3.5-7mg/kg

Amikacin dosing: 15mg/kg

● LDEI: (Levels should always be drawn to verify that trough is less than 1.)

3 methods

 

Method 1: "Standard" dosing is generally 1.5mg/kg q8. Method 1 entails giving total daily dose (4.5mg/kg) q24.

 

Method 2: Give a large dose and tailor the dosing interval based on the patients renal function. An example of this is the Hartford method.5 Give 7mg/kg of Gent/Tobra. Draw a single random level 6-14 hours after the infusion, and base dosing interval on the following nomogram.

 

 

There is also a nomogram based on 5mg/kg dosing.4

 

 

There is also a nomogram based on Amikacin 15mg/kg

 

 

 

 

Method 3: Give dose every 24 hours and tailor dose to patient's renal function.

 

CrCl (ml/min)

Gilbert, et al.2 dosing weighta

Prins, et al.3 dosing weightb

≥ 80

5.1

4.0

61-80

3.9

3.25

51-60

3.6

3.25

30-50

3.0

2.5

< 30

Not used

2.0

Dosing Weights:

a Total body weight if TBW/IBW < 1.35. If TBW/IBW ≥ 1.35, use adjusted body weight.

b Total body weight

 

 

Sources:

 

  1. Murphy, JE. Aminoglycosides (AHFS 8:12.02). In: Murphy, JE. Clinical Pharmacokinetics. 3rd ed. Bethesda, MD: ASHP, 2005; 23-58
  2. Gilbert DN, Lee BL, Dworkin RJ, Leggett JL, Chambers HF, Modin G, Tauber MG, Sande MA. A randomized comparison of the safety and efficacy of once-daily gentamicin or thrice-daily gentamicin in combination with ticarcillin-clavulanate. Am J Med. 1998 Sep;105(3):182-91.
  3. Prins JM, Weverling GJ, de Blok K, van Ketel RJ, Speelman P. Validation and nephrotoxicity of a simplified once-daily aminoglycoside dosing schedule and guidelines for monitoring therapy. Antimicrob Agents Chemother. 1996 Nov;40(11):2494-9.
  4. Anaizi N. Once-daily dosing of aminoglycosides. A consensus document. Int J Clin Pharmacol Ther. 1997 Jun;35(6):223-6.
  5. Nicolau DP, Freeman CD, Belliveau PP, Nightingale CH, Ross JW, Quintiliani R. Experience with a once-daily aminoglycoside program administered to 2,184 adult patients. Antimicrob Agents Chemother. 1995 Mar;39(3):650-5.