The basic formula for calculating drug dosages is very easy to recall and use.  Just put the numbers into the correct place on the formula.  Remember that in order to do any medical mathematics the dosage must be alike.  Conversions may be necessary before you use the formula.

              

       

 

 

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Lets work a problem

Medication order is Cefaclor (Ceclor) 500 mg PO b. i. d.(twice a day)

What is available from the pharmacy is Ceclor 250 mg capsules.

Using the formula

 

D is the desired dose or 500 mg of Ceclor

H is the drug available is 250 mg of Ceclor

V is the vehicle (drug form) capsule

A is the amount to give this is still an unknown

 

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