dosing of aminoglycosides

Q: For aminoglycoside dosing, obesity is defined as a Total Body Weight (TBW) greater than what percentage of the Ideal Body Weight (IBW)? (select one)

A) 50%  

B) 100% 

C) 125% 

D) Can't be determined

Answer: C

The first principle of aminoglycoside administration, regardless of the method of administration, is to determine the dosing weight. Patients are usually categorized as underweight, near IBW, and obese.

IBW calculation for males and females differ:

• IBW, in kg (males) = 50 + (2.3 x inches above 60 inches)
• IBW, in kg (females) = 45.5 + (2.3 x inches above 60 inches)

For underweight patients, TBW is used.

For patients whose weight is 1 to 1.25 times their IBW, the IBW is used.

For aminoglycoside dosing, obesity is defined as a TBW greater than 125 percent of the IBW, and for such patients, the adjusted body weight (AdjBW) is used with the formula:

• AdjBW, in kg = IBW + [0.4 x (TBW - IBW)]

#pharmacology

References:

1. Grucz TM, Kruer RM, Bernice F, Lipsett PA, Dorman T, Sugrue D, Jarrell AS. Aminoglycoside Dosing and Volume of Distribution in Critically Ill Surgery Patients. Surg Infect (Larchmt). 2020 Dec;21(10):859-864. doi: 10.1089/sur.2020.012. Epub 2020 Apr 17. PMID: 32302517.

2. Ross AL, Tharp JL, Hobbs GR, McKnight R, Cumpston A. Evaluation of extended interval dosing aminoglycosides in the morbidly obese population. Adv Pharmacol Sci. 2013;2013:194389. doi: 10.1155/2013/194389. Epub 2013 Aug 19. PMID: 24023540; PMCID: PMC3760189.

3. Richard H Drew - Dosing and administration of parenteral aminoglycosides - UptoDate @ https://www.uptodate.com/contents/dosing-and-administration-of-parenteral-aminoglycosides (last accessed November 29, 2023)