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Prescribing in the Larger Adult

Consider larger doses in the patients who weigh > 130 kg.

In This Section

General Advice

Pharmacokinetic Considerations

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General Advice


Figure 1: Proportion of fat mass and fat-free mass in normal weight and larger-weight patients.

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Pharmacokinetic Considerations

Loading Doses

Maintenance Doses

Using renal function estimates

Medicines of note when prescribing in larger adults

Beta lactam antibiotics (penicillins, cephalosporins etc.): larger doses should be used due to increased renal function. Use upper limit of normal dosing unless there is renal impairment.

Enoxaparin: Use actual bodyweight. Avoid 1.5 mg/kg every 24 hours in patients weighing over 100 kg as doses greater than 150 mg every 24 hours are expected to increase bleeding risk. If the calculated dose of enoxaparin using 1.5 mg/kg is greater than 150 mg every 24 hours, use 1 mg/kg and give it every 12 hours if creatinine clearance is at least 60 mL/min. We also recommend checking anti-Xa levels.

Aciclovir: Use ideal body weight for intravenous dosing.

Weight terms, definitions, and equations

Weight terms



Total body weight

Actual body weight of the person

Total kg

Ideal body weight

The optimal weight associated with maximum life expectancy for a given height

Male (kg) = 50 + [0.9 ×(Height (cm) − 154)]

Female (kg) = 45.5+ [0.9 × (Height(cm)–154)]

Adjusted body weight

Calculation adjustment for someone's actual body weight when they are overweight or obese

IBW (kg) + 0.4 (TBW (kg) – IBW (kg))

Lean body weight

Patient’s weight with adipose tissue removed

Formula as seen above

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Topic Code: 93237