Question

The pediatric starting dose of ritonavir (NORVIR) is 250 mg/m2 by mouth twice daily. The available oral solution contains 600 mg of ritonavir in each 7.5 mL of solution. The correct volume and corresponding quantity of ritonavir to be administered to a child with a body surface area of 0.75 m2 per dose is:

a. 5.6 mL (450.4 mg)

b. 2.8 mL (450.4 mg)

c. 2.8 mL (225.2 mg)

d. 2.3 mL (187.5 mg)

Answer 1

To determine the correct volume of ritonavir to administer to a child with a BSA of 0.75
`m^2`, the dose of 250 mg/
`m^2` is multiplied by the BSA to get 187.5 mg. Converting this dose to volume using the solution's concentration results in 2.3 mL containing 187.5 mg of ritonavir.

Step-by-step explanation:

The student's question calculates the correct volume of the ritonavir oral solution to administer to a child based on their body surface area (BSA). The pediatric starting dose is given as 250 mg/
`m^2` and we know the child's BSA is 0.75
`m^2`. The concentration of the oral solution is 600 mg of ritonavir in each 7.5 mL.

To find the correct dose in milligrams, we multiply the dose per BSA by the child's BSA:

250 mg/
`m^2` × 0.75
`m^2` = 187.5 mg

Next, to convert this dose into the correct volume of the oral solution, we use the concentration of the solution as follows:

187.5 mg × (7.5 mL / 600 mg) = 2.34375 mL

When rounding to the nearest tenth, the volume becomes 2.3 mL, which contains 187.5 mg of ritonavir, matching option d.