Hi Michelle,

I’ll give you an example of why we use body surface area (BSA) before going over the calculations – maybe that will help make it clear.  A typical 7 year old has a BSA of about 1 square meter (m2).  A typical grown man has a BSA of about 2 square meters.  If the child was taking 10mg of Cortef daily, and the man was taking 20mg of Cortef daily, they would be taking the same dose per square meter. 

To figure the dose per square meter, just divide the total daily dose by the individual’s BSA.  For the child, 10mg/1m2 = 10mg/m2 (that reads 10 milligrams per square meter).  For the adult male, 20mg/2m2 = 10mg/m2 as well.  The man takes more drug, but his dose per square meter is the same.

Taty’s BSA is about 1.5m2 and her total daily dose is 22.5mg.  If you divide 22.5 by 1.5, you get 15, which is awfully close to the 14.5 your endo quoted.  I suspect he was using a BSA of 1.55m2 instead of 1.5m2.  It’s easy to be a little off when you are using the printed charts rather than the computerized version, and there are several methods of computing BSA.  That’s where he got the number 14.5.  He’s talking about her dose per square meter.

It’s fine to compare doses with other parents and with the reference materials, but none of that really matters if the dose isn’t right for your child.  Your child’s weight and growth should be important considerations in determining her optimal dosage.  The labs are another factor.

Clearer?

LauraK