Dosing of antimicrobials in obesity
From IDWiki
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 | 2-3 g IV q6-8h 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
