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)
|
[math]\displaystyle{ \frac{weight}{height^{2}} }[/math]
|
kg and m
|
| Body surface area (BSA) (m2)
|
[math]\displaystyle{ BSA = \sqrt{\frac{height \times weight}{3600}} }[/math]
|
kg and cm
|
| Ideal body weight (IBW) (kg)
|
male: [math]\displaystyle{ 50 + 2.3 \times \small{\text{(inches over 5 ft)}} }[/math]
|
in inches
|
| female: [math]\displaystyle{ 45.5 + 2.3 \times \small{\text{(inches over 5 ft)}} }[/math]
|
| Adjusted body weight (ABW) (kg)
|
[math]\displaystyle{ IBW + C \times (TBW - IBW) }[/math]
|
C = 0.3 to 0.4
|
| Lean body weight (LBW) (kg)
|
male: [math]\displaystyle{ \frac{9270 \times TBW}{6680} + 216 \times BMI }[/math]
|
|
| female: [math]\displaystyle{ \frac{9270 \times TBW}{8780} + 244 \times BMI }[/math]
|
Antibiotics
β-lactams
Penicillins
Cephalosporins
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
|
15mg/kg
|
Use ABW0.4
|
Use Hartford nomogram with a (halved) random level
|
| Gentamicin
|
7mg/kg
|
Use ABW0.4
|
Use Hartford nomogram with a random level
|
| Tobramycin
|
7mg/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
