Question

The dose of ofatumumab (Arzerra) for a patient is 300 mg. In preparing an IV infusion, a pharmacist draws the calculated volume of drug from a 50-mL vial containing 1 g of the drug. This quantity is then added to a 1-L bag of normal saline. The infusion is programmed to flow at a rate of drug of 3.6 mg per hour.

(a) What volume (in mL) of the drug from the vial is needed for the patient's dose?

(b) What is the rate of flow needed (in mL/min) to administer the dose to the patient? Express to the nearest thousandth (3 decimal places)

(c) How many hours are needed to administer the dose to this patient? Express to nearest tenth of an hour.

Answer 1

a) What volume (in mL) of the drug from the vial is needed for the patient's dose?

Here it is mentioned that patient needs 300mg and what we have in hour hand is 1g(1000mg) in 50ml vial.So the formula to calculate the volume of mdicine to be drawn is

(D/H) X Q

D is the dose we need,H is the dose of drug in our hand and Q is the quantity.When we put the values in the formula it become (300 /1000) x 50 = 15 ml of drug is needed.

b). What is the rate of flow needed (in mL/min) to administer the dose to the patient?

Here it is said that the dose for the patient to be transfused is 3.6mg per hour.So we have to calculate how much ml make 3.6mg ( after mixing in 1liter,1000 ml normal saline)

Here also we can apply the same formula

(D/H) X Q

D is the dose we need,H is the dose of drug in our hand and Q is the quantity.When we put the values in the formula it become (3.6 /300) x 1000 = 12 ml of drug is needed.So we got that 12 ml is 3.6 mg and this will be the flow rate in an houre (12 ml/ hour),when we see the flow rate in minute in become 12 / 60 = 0.2ml per minute

c).  How many hours are needed to administer the dose to this patient?

so we have seen that in an hour 12 ml we need to infuse to complete 3.6mg

so to calculate the the hours needed for complet the 300mg dose ,we need to devide the total fluid by the volume infused in one hour

1000 / 12 = 83.33 hours needed to complete the adviced 300mg