Dosing of antimicrobials in obesity: Difference between revisions

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== Calculating Body Weight ==
== Calculating Body Weight ==
Weight-based dosing can use total body weight (TBW) in some instances, but often requires adjustments.

{| class="wikitable"
{| class="wikitable"
! Statistic !! Equation (Male) !! Equation (Female) !! Notes
! Statistic !! Equation !! Notes
|-
|-
| '''[https://www.mdcalc.com/body-mass-index-bmi-body-surface-area-bsa Body mass index]''' (BMI) (kg/m<sup>2</sup>)
| '''[https://www.mdcalc.com/body-mass-index-bmi-body-surface-area-bsa Body mass index]''' (BMI) (kg/m<sup>2</sup>)
| colspan=2 | weight, kg / (height, m)<sup>2</sup>
| <math>\frac{weight}{height^{2}}</math>
| kg and m
|
|-
|-
| '''[https://www.mdcalc.com/body-mass-index-bmi-body-surface-area-bsa Body surface area]''' (BSA) (m<sup>2</sup>)
| '''[https://www.mdcalc.com/body-mass-index-bmi-body-surface-area-bsa Body surface area]''' (BSA) (m<sup>2</sup>)
| colspan=2 | (height, cm × weight, kg / 3600)<sup>1/2</sup>
| <math>BSA = \sqrt{\frac{height \times weight}{3600}}</math>
| kg and cm
|
|-
|-
| '''[https://www.mdcalc.com/ideal-body-weight-adjusted-body-weight Ideal body weight]''' (IBW) (kg)
| rowspan=2 | '''[https://www.mdcalc.com/ideal-body-weight-adjusted-body-weight Ideal body weight]''' (IBW) (kg)
| 50 + 2.3 × (inches over 5 ft)
| male: <math>50 + 2.3 \times \small{\text{(inches over 5 ft)}}</math>
| 45.5 + 2.3 × (inches over 5 ft)
| rowspan=2 | in inches
|
|-
| female: <math>45.5 + 2.3 \times \small{\text{(inches over 5 ft)}}</math>
|-
|-
| '''[https://www.mdcalc.com/ideal-body-weight-adjusted-body-weight Adjusted body weight]''' (ABW) (kg)
| '''[https://www.mdcalc.com/ideal-body-weight-adjusted-body-weight Adjusted body weight]''' (ABW) (kg)
| colspan=2 | IBW + C × (TBW - IBW)
| <math>IBW + C \times (TBW - IBW)</math>
| C = 0.3 to 0.4
| C = 0.3 to 0.4
|-
|-
| '''Lean body weight''' (LBW) (kg)
| rowspan=2 | '''Lean body weight''' (LBW) (kg)
| 9270 × TBW / 6680 + 216 x BMI
| male: <math>\frac{9270 \times TBW}{6680} + 216 \times BMI</math>
| rowspan=2 |
| 9270 × TBW / 8780 + 244 x BMI
|-
| female: <math>\frac{9270 \times TBW}{8780} + 244 \times BMI</math>
|}

== Calculating CrCl ==
[https://globalrph.com/medcalcs/salazar-corcoran-calc/ Salazer-Cocoran equation] is more reliable in obesity but requires both height and weight.

== Antibiotics ==
=== β-lactams ===
==== Penicillins ====

{| class="wikitable" style="width:100%"
! Drug !! Usual Dose !! Obesity !! Notes
|-
| [[Amoxicillin]]
| 250-500 mg q8h
| 1 g PO q8h
|
|
|-
|-
| [[Ampicillin]]
| '''Fat-free weight''' (FFW) (kg)
| 1-2 g q4-6h
| 0.00139 × (height, cm)<sup>2</sup> - 0.0801 × R + 0.187 × TBW + 39.83
| 2 g IV q4h
| 0.00151 × (height, cm)<sup>2</sup> - 0.0344 × R + 0.14 × TBW - (0.158 × age) + 20.387
|
| R = resistance
|-
| [[Nafcillin]]
|
| 2 g IV q4h
|
|-
| [[Piperacillin-tazobactam]]
| 4.5 g IV q8h (q6h for ''Pseudomonas'')
| Prolonged infusion
|
|}

==== Cephalosporins ====
{| class="wikitable" style="width:100%"
! Drug !! Usual Dose !! Obesity !! Notes
|-
| [[Cephalexin]]
| 500-1000 g PO qid
| 1000 g PO qid
|
|-
| [[Cefazolin]]
| 1-2 g IV q8h
| 2 g IV q6h once &ge;120 kg
|
|-
| [[Cefipime]]
| 2 g IV q8h
| 2 g IV q8h prolonged infusion
|
|-
| [[Ceftazidime]]
| 1-2 g IV q8h
| 2 g IV q8h prolonged infusion
|
|-
| [[Ceftazidime-avibactam]]
|
| Usual dose
|
|-
| [[Ceftolozane-tazobactam]]
|
| Usual dose
|
|-
| [[Ceftaroline]]
|
| Consider q8h
|
|}

==== Carbapenems ====
{| class="wikitable" style="width:100%"
! Drug !! Usual Dose !! Obesity !! Notes
|-
| [[Doripenem]]
|
| Consider extended infusion
|
|-
| [[Ertapenem]]
| 1 g IV q24h
| Usual dose
|
|-
| [[Imipenem]]
|
| Usual dose
|
|-
| [[Meropenem]]
| 500 mg q6h (1 g IV q8h for febrile neutropenia)
| Consider prolonged infusion
|
|}

=== Quinolones ===
{| class="wikitable" style="width:100%"
! Drug !! Usual Dose !! Obesity !! Notes
|-
| [[Ciprofloxacin]]
| 500-750 mg PO q12h or 400 mg IV q6-8h
| 400 mg IV q8h or 750 mg PO q12h
|
|-
| [[Levofloxacin]]
| 500-750 mg PO q24h
| Consider up to 1000 mg PO q24h
|
|-
| [[Moxifloxacin]]
| 400 mg q24h
| Usual dose
|
|}

=== Macrolides ===
{| class="wikitable" style="width:100%"
! Drug !! Usual Dose !! Obesity !! Notes
|}

=== Tetracyclines ===
{| class="wikitable" style="width:100%"
! Drug !! Usual Dose !! Obesity !! Notes
|}

=== Aminoglycosides ===
{| class="wikitable" style="width:100%"
! Drug !! Usual Dose !! Obesity !! Notes
|-
| [[Amikacin]]
| 15 mg/kg
| Use ABW<sub>0.4</sub>
| Use Hartford nomogram with a (halved) random level
|-
| [[Gentamicin]]
| 7 mg/kg
| Use ABW<sub>0.4</sub>
| Use Hartford nomogram with a random level
|-
| [[Tobramycin]]
| 7 mg/kg
| Use ABW<sub>0.4</sub>
| Use Hartford nomogram with a random level
|}

=== Others ===
{| class="wikitable" style="width:100%"
! Drug !! Usual Dose !! Obesity !! Notes
|-
| [[Aztreonam]]
|
| 2 g IV q6-8h
|
|-
| [[Colistin]]
| 5 mg CBA/kg IBW x1 loading (max 300 mg) followed by 5 mg/kg/day divided q8h
| Use IBW
| Max 360 mg daily (nephrotoxicity)
|-
| [[Polymyxin B]]
|
| Use ABW<sub>0/4</sub>
| Max 200 mg or 2 MU daily (toxicity)
|-
| [[Clindamycin]]
| 300-450 mg PO q6-8h<br/>600-900 mg IV q8h
| 600 mg IV q6h<br/>900 mg IV q8h<br/>450-600 mg PO q6h<br/>600-900 mg PO q8h
| Max 2700 mg daily, or 4800 mg daily IV if life-threatening
|-
| [[Dalbavancin]]
|
| Usual dose
|
|-
| [[Daptomycin]]
| 4-6 mg/kg q24h
| Use ABW<sub>0.4</sub>
|
|-
| [[Linezolid]]
| 600 mg PO/IV q12h
| Usual dose
|
|-
| [[Oritavancin]]
|
| Usual dose
|
|-
| [[TMP-SMX]]
| Up to 320 mg(TMP) PO q12h<br/>8-10 mg(TMP)/kg<sub>ABW</sub> in divided doses
| Consider ABW<sub>0.4</sub> when doing high dose
|
|-
| [[Telavancin]]
|
| Usual dose
|
|-
| [[Tigecycline]]
|
| Usual dose
|
|-
| [[Vancomycin]]
| 20-25 mg/kg load (max 2.5 g)<br />10-15 mg/kg q12h (maintenance)
| Use TBW; or 25-30 mg/kg load and 15 mg/kg q12h with ABW<sub>0.4</sub>
|
|}
|}


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* Comprehensive Guidance for Antibiotic Dosing in Obese Adults. ''Pharmacotherapy''. 2017;37(11):1415-1431. doi: [https://doi.org/10.1002/phar.2023 10.1002/phar.2023]
* Comprehensive Guidance for Antibiotic Dosing in Obese Adults. ''Pharmacotherapy''. 2017;37(11):1415-1431. doi: [https://doi.org/10.1002/phar.2023 10.1002/phar.2023]


[[Category:Antibiotics]]
[[Category:Antimicrobials]]

Latest revision as of 16:36, 8 June 2023

Calculating Body Weight

Weight-based dosing can use total body weight (TBW) in some instances, but often requires adjustments.

Statistic Equation Notes
Body mass index (BMI) (kg/m2) kg and m
Body surface area (BSA) (m2) kg and cm
Ideal body weight (IBW) (kg) male: Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 50 + 2.3 \times \small{\text{(inches over 5 ft)}}} in inches
female: Failed to parse (unknown function "\small"): {\displaystyle 45.5 + 2.3 \times \small{\text{(inches over 5 ft)}}}
Adjusted body weight (ABW) (kg) C = 0.3 to 0.4
Lean body weight (LBW) (kg) male:
female:

Calculating CrCl

Salazer-Cocoran equation is more reliable in obesity but requires both height and weight.

Antibiotics

β-lactams

Penicillins

Drug Usual Dose Obesity Notes
Amoxicillin 250-500 mg q8h 1 g PO q8h
Ampicillin 1-2 g q4-6h 2 g IV q4h
Nafcillin 2 g IV q4h
Piperacillin-tazobactam 4.5 g IV q8h (q6h for Pseudomonas) Prolonged infusion

Cephalosporins

Drug Usual Dose Obesity Notes
Cephalexin 500-1000 g PO qid 1000 g PO qid
Cefazolin 1-2 g IV q8h 2 g IV q6h once ≥120 kg
Cefipime 2 g IV q8h 2 g IV q8h prolonged infusion
Ceftazidime 1-2 g IV q8h 2 g IV q8h prolonged infusion
Ceftazidime-avibactam Usual dose
Ceftolozane-tazobactam Usual dose
Ceftaroline Consider q8h

Carbapenems

Drug Usual Dose Obesity Notes
Doripenem Consider extended infusion
Ertapenem 1 g IV q24h Usual dose
Imipenem Usual dose
Meropenem 500 mg q6h (1 g IV q8h for febrile neutropenia) Consider prolonged infusion

Quinolones

Drug Usual Dose Obesity Notes
Ciprofloxacin 500-750 mg PO q12h or 400 mg IV q6-8h 400 mg IV q8h or 750 mg PO q12h
Levofloxacin 500-750 mg PO q24h Consider up to 1000 mg PO q24h
Moxifloxacin 400 mg q24h Usual dose

Macrolides

Drug Usual Dose Obesity Notes

Tetracyclines

Drug Usual Dose Obesity Notes

Aminoglycosides

Drug Usual Dose Obesity Notes
Amikacin 15 mg/kg Use ABW0.4 Use Hartford nomogram with a (halved) random level
Gentamicin 7 mg/kg Use ABW0.4 Use Hartford nomogram with a random level
Tobramycin 7 mg/kg Use ABW0.4 Use Hartford nomogram with a random level

Others

Drug Usual Dose Obesity Notes
Aztreonam 2 g IV q6-8h
Colistin 5 mg CBA/kg IBW x1 loading (max 300 mg) followed by 5 mg/kg/day divided q8h Use IBW Max 360 mg daily (nephrotoxicity)
Polymyxin B Use ABW0/4 Max 200 mg or 2 MU daily (toxicity)
Clindamycin 300-450 mg PO q6-8h
600-900 mg IV q8h 		600 mg IV q6h
900 mg IV q8h
450-600 mg PO q6h
600-900 mg PO q8h 		Max 2700 mg daily, or 4800 mg daily IV if life-threatening
Dalbavancin Usual dose
Daptomycin 4-6 mg/kg q24h Use ABW0.4
Linezolid 600 mg PO/IV q12h Usual dose
Oritavancin Usual dose
TMP-SMX Up to 320 mg(TMP) PO q12h
8-10 mg(TMP)/kgABW in divided doses 		Consider ABW0.4 when doing high dose
Telavancin Usual dose
Tigecycline Usual dose
Vancomycin 20-25 mg/kg load (max 2.5 g)
10-15 mg/kg q12h (maintenance) 		Use TBW; or 25-30 mg/kg load and 15 mg/kg q12h with ABW0.4

Further Reading

  • Comprehensive Guidance for Antibiotic Dosing in Obese Adults. Pharmacotherapy. 2017;37(11):1415-1431. doi: 10.1002/phar.2023
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