Laura-I don't know about the absorption rates, but I do have a site that was recently posted on this board. It is the formula used to calculate the correct dosage based on your child's body surface area. I believe you need the height and weight. Go to www.halls.md/body-surface-area/bsa.htm. Somebody who posted recently seemed to know alot more about this than me! Hang in there-you'll get through this! Good luck!