Drug Dosing in Obesity Reference Table

• Dose using ideal body weight (per package insert)
• No information about dose adjustments in extremely obese patients exists

• Dose using a 40% adjusted body weight

• Dose using ideal body weight
• The use of ideal body weight has been shown to be associated with a more predictable muscle strength recovery within 60 minutes and a lack of need for antagonism compared to total body weight

• Dose using total body weight
• VTE prophylaxis: if BMI ≥ 40 mg/m² increase dose by 30%
• VTE treatment: once-daily dosing (200 units/kg daily) probably okay (unlike enoxaparin)
• Anti-Xa level monitoring probably not necessary unless weight > 190 kg

• Dose using total body weight

• Dose using ideal body weight

• No kinetic data has been published -- titrate to goal MAP

• No kinetic data has been published -- titrate to goal MAP

• Dose using total body weight
• VTE prophylaxis: if BMI ≥ 40 mg/m² increase dose by 30%
• VTE treatment: avoid once-daily dosing if BMI > 27 kg/m² (eg, do not use 1.5 mg/kg daily)
• Anti-Xa level monitoring probably not necessary unless weight > 190 kg

• No kinetic data has been published -- titrate to goal MAP

• VTE prophylaxis: use standard dosing (2.5 mg daily)
• In a study of patients with BMI > 40 kg/m², 53% of patients of patients had anti-Xa levels were within or above target range

• Dose using a 40% adjusted body weight

^9,10,11

• Dose using adjusted body weight (preferred), ideal body weight, or actual body weight with a dosing cap
• Studies have shown that using actual body weight (without a dose cap) is associated with a higher aPTT value
• Heparin infusions should be titrated to an aPTT goal (usually every 6-8 hours until stable)

• For bolus doses, use total body weight
• For continuous infusions, use ideal body weight
• In obese patients, lorazepam volume of distribution increases proportionally to body weight. Therefore, doses based on total body weight are required to reach the same initial serum concentration
• Once at goal sedation, continuous infusions should use ideal body weight because lorazepam clearance is not affected by total body weight.

¹³

• Dose using ideal body weight and consider less frequent dosing
• In a study of 6 obese and non-obese patients, methylprednisolone volume of distribution was unaffected by body size, but clearance was significantly reduced in patients with obesity

• For bolus doses, use total body weight
• For continuous infusions, use ideal body weight
• In obese patients, midazolam volume of distribution increases proportionally to body weight. Therefore, doses based on total body weight are required to reach the same initial serum concentration
• Once at goal sedation, continuous infusions should use ideal body weight because midazolam clearance is not affected by total body weight.

• No kinetic data has been published -- titrate to goal MAP

• Use standard dosing (no adjustment for obesity)

• For loading doses, use the following equation for dosing weight: Dosing weight = Ideal + 1.33 * (Actual - Ideal)
• Ideal body weight is calculated using the Devine equation
• Obese patients will require more than their actual body weight for a phenytoin loading dose

• Dose using total body weight
• For continuous infusions, titrate drip to desired sedation goal
• Note that the cardiovascular effects of large propofol doses (hypotension) are poorly described and may be problematic

• Body weight does not strongly correlate to reduction in uric acid levels
• Consider fixed, single doses irrespective of body weight

^18,2,7

• Dose using ideal body weight
• For continuous infusion, titrate to pain control

• Dose using ideal body weight

^12,20

• Dose using total body weight
• Obese patients may have increased pseudocholinesterase activity, which metabolizes succinycholine
• This recommendation is only based on expert opinion -- there is nearly no compelling evidence

• Dose using total body weight
• VTE prophylaxis: if BMI ≥ 40 mg/m² increase dose by 30%
• VTE treatment: once-daily dosing (175 units/kg daily) probably okay (unlike enoxaparin)
• Anti-Xa level monitoring probably not necessary unless weight > 190 kg

• Dose using a 40% adjusted body weight

• Dose using toal body weight
• Vancomycin dose should be adjusted based on vancomycin trough levels once at steady state (usually 3-4 doses)

• Dose using ideal body weight
• Although volume of distribution and clearance are unchanged in obese patients, doses using actual body weight may have prolonged neuromuscular blockade.

• Dose using lean body weight (LBW 2005 equation)
• LBW2005 correlates to AUC better than total body weight, although both are poor predictors of voriconazole levels due to a high degree of interpatient variability (R² < 0.50)
• Voriconazole dose should be adjusted based on voriconazole trough levels once at steady state (usually 5-7 days of therapy)