Related | Selecting Appropriate Dosing Weight for Antimicrobial Medications
Appendix B. Selecting Appropriate Dosing Weight for Antimicrobial Medications
From: Renal Function-Based Dose Adjustments – Adult – Inpatient/Ambulatory – Consensus Care Model
Contact for Content: Lucas Schulz, PharmD, BCPS (AQ-ID); 608-890-8617; LSchulz2@uwhealth.org
Definitions and Equations:
• TBW = Total body weight (also called “Actual Body Weight”)
• IBW = ideal body weight
o IBW in kg (male) = 50 𝑘𝑘𝑘𝑘 + 2.3 × [𝐻𝐻𝑎𝑎𝑖𝑖𝑘𝑘ℎ𝐻𝐻 (𝑖𝑖𝑖𝑖𝐵𝐵ℎ𝑎𝑎𝑒𝑒)− 60]
o IBW in kg (female) = 45.5 𝑘𝑘𝑘𝑘 + 2.3 × [𝐻𝐻𝑎𝑎𝑖𝑖𝑘𝑘ℎ𝐻𝐻 (𝑖𝑖𝑖𝑖𝐵𝐵ℎ𝑎𝑎𝑒𝑒)− 60]
• AdjBW = adjusted body weight
o AdjBW in kg = 𝐼𝐼𝐴𝐴𝐴𝐴(𝑘𝑘𝑘𝑘) + 0.4 × [𝐴𝐴𝐴𝐴𝐴𝐴(𝑘𝑘𝑘𝑘)− 𝐼𝐼𝐴𝐴𝐴𝐴(𝑘𝑘𝑘𝑘)]
Appendix B: Selecting appropriate dosing weight for antimicrobial dosing (all recommendations are UW
Health GRADE Low-moderate quality evidence, conditional recommendation)
If patient TBW less
than IBW, use this
column
If patient is non-
obese and
TBW is greater
than IBW, use this
column
If patient is obese
(BMI >30 kg/m2),
use this column
Antibiotics
Aminoglycosides
TBW
IBW AdjBW1
Colistin IBW IBW2,3
Daptomycin IBW IBW4
Polymyxin B TBW AdjBW5-9
Trimethoprim/Sulfamethoxazole TBW AdjBW10
Vancomycin TBW TBW11,12
Antivirals
Acyclovir
TBW
IBW IBW10
Ganciclovir TBW AdjBW10
Foscarnet TBW AdjBW
10; see
footnote A
Antifungals
Liposomal amphotericin
TBW
TBW AdjBW
13; see
footnote B
Flucytosine IBW IBW14,15
Voriconazole TBW AdjBW16,17
Miscellaneous
Bezlotoxumab
TBW
TBW TBW13
Ethambutol IBW IBW14
Pyrazinamide IBW IBW14,15
A Use TBW for the indication of ganciclovir-resistant cytomegalovirus
B Consider IBW if risk of nephrotoxicity outweighs risk of infection
Copyright © 2020 University of Wisconsin Hospitals and Clinics Authority. All Rights Reserved. Printed with Permission
Contact: CCKM@uwhealth.org Last Revised: 08/2020
Effective 12/15/2020. Contact CCKM@uwhealth.org for previous versions
Appendix B References
1. Bauer LA, Edwards WA, Dellinger EP, Simonowitz DA. Influence of weight on aminoglycoside pharmacokinetics
in normal weight and morbidly obese patients. European journal of clinical pharmacology. 1983;24(5):643-647.
2. Garonzik SM, Li J, Thamlikitkul V, et al. Population pharmacokinetics of colistin methanesulfonate and formed
colistin in critically ill patients from a multicenter study provide dosing suggestions for various categories of
patients. Antimicrobial agents and chemotherapy. 2011;55(7):3284-3294.
3. Ortwine JK, Kaye KS, Li J, Pogue JM. Colistin: understanding and applying recent pharmacokinetic advances.
Pharmacotherapy. 2015;35(1):11-16.
4. Ng JK, Schulz LT, Rose WE, et al. Daptomycin dosing based on ideal body weight versus actual body weight:
comparison of clinical outcomes. Antimicrobial agents and chemotherapy. 2014;58(1):88-93.
5. Sandri AM, Landersdorfer CB, Jacob J, et al. Population pharmacokinetics of intravenous polymyxin B in
critically ill patients: implications for selection of dosage regimens. Clin Infect Dis. 2013;57(4):524-531.
6. Pai MP. Polymyxin B dosing in obese and underweight adults. In: Clin Infect Dis. Vol 57. United
States2013:1785.
7. Onufrak NJ, Rao GG, Forrest A, et al. Critical Need for Clarity in Polymyxin B Dosing. Antimicrob Agents
Chemother. 2017;61(5).
8. Pogue JM, Ortwine JK, Kaye KS. Are there any ways around the exposure-limiting nephrotoxicity of the
polymyxins? Int J Antimicrob Agents. 2016;48(6):622-626.
9. Pogue JM, Ortwine JK, Kaye KS. Clinical considerations for optimal use of the polymyxins: A focus on agent
selection and dosing. Clin Microbiol Infect. 2017;23(4):229-233.
10. Polso AK, Lassiter JL, Nagel JL. Impact of hospital guideline for weight-based antimicrobial dosing in morbidly
obese adults and comprehensive literature review. Journal of clinical pharmacy and therapeutics.
2014;39(6):584-608.
11. Rybak MJ, Lomaestro BM, Rotschafer JC, et al. Therapeutic monitoring of vancomycin in adults summary of
consensus recommendations from the American Society of Health-System Pharmacists, the Infectious Diseases
Society of America, and the Society of Infectious Diseases Pharmacists. Pharmacotherapy. 2009;29(11):1275-
1279.
12. Srinivas NR. Influence of Morbidly Obesity on the Clinical Pharmacokinetics of Various Anti-Infective Drugs:
Reappraisal Using Recent Case Studies-Issues, Dosing Implications, and Considerations. American journal of
therapeutics. 2016.
13. Amsden JR, Slain D. Antifungal Dosing in Obesity: A Review of the Literature. Current Fungal Infection Reports.
2011;5(2):83.
14. Vermes A, Guchelaar HJ, Dankert J. Flucytosine: a review of its pharmacology, clinical indications,
pharmacokinetics, toxicity and drug interactions. The Journal of antimicrobial chemotherapy. 2000;46(2):171-
179.
15. Tucker CE, Lockwood AM, Nguyen NH. Antibiotic dosing in obesity: the search for optimum dosing strategies.
Clinical obesity. 2014;4(6):287-295.
16. Koselke E, Kraft S, Smith J, Nagel J. Evaluation of the effect of obesity on voriconazole serum concentrations.
The Journal of antimicrobial chemotherapy. 2012;67(12):2957-2962.
17. Sebaaly JC, MacVane SH, Hassig TB. Voriconazole concentration monitoring at an academic medical center.
American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System
Pharmacists. 2016;73(5 Suppl 1):S14-21.
Copyright © 2020 University of Wisconsin Hospitals and Clinics Authority. All Rights Reserved. Printed with Permission
Contact: CCKM@uwhealth.org Last Revised: 08/2020
Effective 12/15/2020. Contact CCKM@uwhealth.org for previous versions
Appendix B. Selecting Appropriate Dosing Weight for Antimicrobial Medications