NBS II Lecture' material

Formulas for computing drug dosages




Adult Dose

Dose on hand dose desired
-------------------------- = ------------------------------
Quantity on hand X (quantity desired)


Example:

Amoxicillin, 625 mg PO, is ordered. It is supplied as a liquid preparation containing 250 mg in 5 ml. How much does the nurse administer?

250 mg 625 mg
-------------- = ---------------
5 ml X ml

3125 = 250 X
X = 12, 5 ml


Another formula


Dose desired
--------------------- X quantity on hand = desired quantity
Dose on hand

Example:

625 mg
----------- X 5 ml = 12,5 ml
250 mg

Pediatric calculations

BSA (child)
----------------- X adult dose = child’s dose
BSA (adult)

Another formula (Clark’s rule)

Child’s weight (pound)
--------------------------------- X adult dose = child’s dose
150

Body Surface Area a.k.a BSA available in Fundamental of Nursing by Carol Taylor page 719