Question

Gentamicin 1,390 mg IV once a week for 7 weeks is ordered, to infuse in 100 mL over 30 minutes. The patient is 155 cm tall and weighs 45 kg. The recommended dose is 1,000 mg/m2 once weekly for up to 7 weeks.

a). Is the prescribed dose safe?

b). At what rate will you set the pump in mL/h?

Answer 1

Ordered dose is 1390 mg once a week for 7 weeks , to infuse in 100 ml over 30 minutes

Recommended dose is 1000mg/m^2 once weekly for upto 7 weeks

a) if weight of patient is 45kg

Height is 155 cm or 1.55 m

Then BMI = Weight in kg /Height^2 in metres = 45/1.55^2 = 45/ 2.40 = 18.75 m^2

If in 1 metre square recommended dose is = 1000mg

Then in 18.75 metre^2 recommended dose will be = 1000×18.75= 18750 mg

Thus recommended dose for this patient whose BMI is 18.75m^2 is 18750mg

If it is recommended for 7 week then for 1 week ( once a week) recommended dose will be = 18750/7 = 2678.5 mg

Thus recommend dose for once a week for this patient is = 2678.5 mg

And ordered dose once week is 1390 mg which is lesser than recommended dose

So it is safe to prescribe.

2. Rate at which infusion pump will be set , if to infuse 100 ml over 30 minutes

Thus in one hour ml to be infused will be same as in 60 minutes , so

Let x is ml/hr which is infusion rate , thus

=> 100/30= x/60 , x = 200 ml/hr

So flow rate will be 200 ml/hour at which infusion pump will be set

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