QUESTION 1
Given that they weigh 7 stone 13lb and are 5′4′′ tall, use the Mosteller (1987) formula (Figure 1) for body surface area to calculate the dose determining body surface area in m2.
- Weight: 7 stone = 7×14lb = 98lb, therefore 7 stone 13 lb = 98+13 lb= 111 lb
- 1 lb = 454 g = 0.454 kg
- 111 lb × 0.454 kg/lb = 50.4 kg
- Height: 5’ = 5 × 12inches/foot = 60 inches
- 60” + 3” = 63” tall
- 1” = 2.54cm; 63” × 2.54cm/” = 160 cm
Putting these into Mosteller:
- BSA (m2) = 50.3kg × 160 cm = 8064 kg/cm
- 8064 /3600 = 2.24
- ✓2.24 = 1.5 m2
QUESTION 2
Using your answer to question 1, calculate the cyclophosphamide dose required. The clinicians would like to use the lower end of the summary of product characteristics (2014) recommended dose of cyclophosphamide for autoimmune disorders; 500 mg/m2 every fortnight initially.
- 1.5 m2 × 500 mg/m2 = 750 mg
QUESTION 3
How much mesna is required for each dose for this patient?
- Cyclophosphamide dose = 750 mg = 100%
- 20% of 750 mg = 150 mg