Adjusted Body Weight — Obese Patients

The Adjusted Body Weight (ABW) formula is used in clinical practice for pharmacokinetic dosing and nutritional calculations in obese patients (BMI >30 kg/m²), where using actual total body weight (TBW) would overestimate drug distribution or caloric requirements, and using ideal body weight (IBW) would underestimate them. The formula ABW = IBW + 0.4 × (TBW − IBW) reflects the empirically derived estimate that approximately 40% of excess adipose tissue participates in drug distribution for lipophilic medications (e.g., aminoglycosides, vancomycin, digoxin). For hydrophilic drugs (e.g., heparin, neuromuscular blockers), IBW or lean body weight (LBW) is typically used.