Question

methotrexate 4 mg PO daily for a child with leukemia

Child weighs 70 lb and is 67 inches tall

The safe dosage range is 3 – 3.5 mg per square meter per day

A. Calculate the BSA for this child.

B. Is the BSA needed to calculate the safe dosage range, in mg per day, for this child? Why or why not?

C. Calculate the safe dosage range, in mg per day, for this child.

D. Is the order safe? Why or why not? Explain.

Answer 1

A)

Du Bios formula

BSA = 0.007184 × W0.425 × H0.725

Height=67inch=170.1cm

Weight=70Ib=31.75kg

BSA=0.007184 × 31.75squared 0.425 × 170.1squared 0.725=1.29 meeter square

Below are some of the most popular formulas for estimating BSA

Du Bois formula:
BSA = 0.007184 × W0.425 × H0.725

Mosteller formula:
BSA = = 0.016667 × W0.5 × H0.5

Haycock formula:
BSA = 0.024265 × W0.5378 × H0.3964

Gehan and George formula:
BSA = 0.0235 × W0.51456 × H0.42246

Boyd formula:
BSA = 0.03330 × W(0.6157 - 0.0188 × log10(W) × H0.3

Fujimoto formula:
BSA = 0.008883 × W0.444 × H0.663

Takahira formula:
BSA = 0.007241 × W0.425 × H0.725

Schlich formula:
Women BSA = 0.000975482 × W0.46 × H1.08
Men BSA = 0.000579479 × W0.38 × H1.24

B) Is the BSA needed to calculate the safe dosage range, in mg per day, for this child? Why or why not?

Yes,In the given senario the child with leukemia;
BSA is used for the purposes over body weight because it is a more accurate indicator of metabolic mass (the body's need for energy), where metabolic mass can be estimated as fat-free mass since body fat is not metabolically active.
BSA is used in various hospital settings such as determining cardiac index (to relate a person's heart performance to their body size) .
And also it is used to calculate the dosages for chemotherapy (a category of cancer treatment). While dosing for chemotherapy is often determined using a patient's BSA.

C)Methotrexate dose calculate as 50 mg per m2(meeter square)(rounded to nearest 0.1 mg),based on Du Bios formula for BSA

=50 × 1.29

=64.5mg

Safe dosage range is 64.5 mg

D) Is the order safe? Why or why not? Explain.

For the maximum safety purpose the medical professionals they consider the BSA .

However,
There exist arguments against the use of BSA to determine medication dosages that have a narrow therapeutic index – the comparison of the amount of a substance necessary to produce a therapeutic effect, to the amount that causes toxicity.