Question 1

How should I calculate doses for patients with BMI ≥40 kg/m²?

Accepted Answer

For severely obese patients (BMI ≥40), drug pharmacokinetics may be altered beyond simple weight metrics. Consider using ideal body weight for highly lipophilic drugs and adjusted body weight for hydrophilic drugs. For drugs where data in obesity are limited, consult a clinical pharmacist and consider therapeutic drug monitoring.

Question 2

What weight should I use for paediatric dosing?

Accepted Answer

For children, use actual body weight (kg) for all weight-based calculations. Body surface area (Mosteller or DuBois formula) is used for chemotherapy and some antifungals. The tool accepts either weight or BSA depending on the drug selected.

Question 3

How do I dose unfractionated heparin by weight?

Accepted Answer

For VTE and ACS, weight-based heparin protocols use actual body weight. A typical loading dose is 80 units/kg (maximum 10,000 units), followed by an infusion of 18 units/kg/h (maximum 2,500 units/h), with aPTT monitoring per the institutional nomogram. In obesity, some protocols cap the bolus and initial infusion to avoid supratherapeutic aPTT.