Question

A physician writes the following order: gentamicin 1.5 mg/kg/dose every 8 hours. The patient is an obese man, 33 years of age: so gentamicin must be dosed using an adjusted body weight (ABW) with a dose correction factor of 0.4. The patient is 185 kg and is 69 inches tall. Calculate the amount in milligrams of each individual dose.

Answer 1

To calculate the gentamicin dose for the obese patient, you need to determine the adjusted body weight (ABW) based on the patient's ideal body weight (IBW) and actual weight using a correction factor. After calculating IBW and ABW, you then use the ABW to determine the mg per dose. The patient's gentamicin dosage is 174.63 mg per dose, to be administered every 8 hours.

Step-by-step explanation:

To calculate the gentamicin dosage for an obese patient using adjusted body weight (ABW), first calculate the ABW using the formula:

ABW = IBW + 0.4(Actual weight - IBW)

Where IBW (Ideal Body Weight) for men is: 50 kg + 2.3 kg for each inch over 5 feet (60 inches).

The patient is 69 inches tall, so the IBW is calculated as follows:

IBW = 50 kg + 2.3 kg x (69 - 60) = 50 kg + 2.3 kg x 9 = 70.7 kg

Now, we use the ABW formula with the patient's actual weight (185 kg):

ABW = 70.7 kg + 0.4(185 kg - 70.7 kg) = 70.7 kg + 0.4(114.3 kg) = 70.7 kg + 45.72 kg = 116.42 kg

Finally, calculate the dose using the patient's ABW:

Dose = 1.5 mg/kg x ABW

Dose = 1.5 mg/kg x 116.42 kg = 174.63 mg per dose, every 8 hours.