QUESTION 1
What is the body surface area for this child?
- 9.98 kg × 77.7 cm = 775.446 kg/cm
- 775.446/3600 = 0.2154
- 0.2154=0.464 m2
- In practice it is also possible to use the ready reckoner nomogram in the BNFC (BNFCb, 2023 Body Surface area), although if you compare it in this case you may notice it over-estimates for the child compared to use of the equation.
QUESTION 2
Calculate the loading and maintenance doses for this child.
- Loading dose: 70 mg/m2 × 0.464 m2 = 32.5 mg
- Maintenance dose: 50 mg/m2 × 0.464 m2 = 23.2 mg
QUESTION 3
What volume of this solution will need to be administered to provide the loading dose?
- Loading dose = 32.5 mg
- Stock solution = 5.2 mg/ml
- 32.5 mg/5.2 mg/ml = 6.25 ml
QUESTION 4
The current drug tariff price for a 50 mg vial of caspofungin is £238.87. Assuming none of a vial can be used to treat additional patients, what is the difference in cost of wasted drug for each maintenance dose compared to the loading dose?
- Cost for 50 mg = £238.87 so cost per mg = £238.87/50 mg = £4.7774/mg
- Wastage from loading dose = 50 mg - 32.5 mg = 17.5 mg
- Wastage from maintenance dose = 50 - 23.2 mg = 26.8 mg
- Difference is wasted amounts = 26.8 mg - 17.5 mg = 9.3 mg
- Cost of 9.3 mg = 9.3 mg × £4.7774/mg = £44.4298 = £44.43 additional wastage