CHAPTER 5: Calculating Doses For Oral Medications

Dose calculation formula

Desired/Have x Quanity

Quantity to dispense formula

Daily use x Days

Days Supply formula

Quantity dispensed/daily use

Weight-Based Dosing formula

mg/kg x kg

BSA Dosing formula

mg/m2 x BSA

Fried’s Rule formula

Months/150 x Adult dose

Young’s Rule formula

Age/(Age + 12) x Adult Dose

Clark’s Rule formula

Weight(lb)/150 x Adult Dose

How many days will an 8 fl oz bottle last if a patient takes 2 tsp TID?

1oz=30mL

8 × 30 = 240

next, 1tsp=5mL

2 × 5 = 10

Calculate daily use: 10 × 3 = 30mL per day

Calculate days supply: 240mL/30mL per day

ASNWER: 8 days

A child weighs 66 lb. What is the child’s weight in kilograms?

66/2.2=30

A child weighs 50 kg. What is the child’s weight in pounds?

50 × 2.2 = 110 lb

Medication dosed at 75mg/m2

Patient BDS = 1.6m2

What dose should be administered?

75 × 1.6 =120

Using Young’s Rule calculate pediatric dose for a 6 year old

Adult dose = 300 mg

6/(6 + 12) x 300

6/18=0.33

0.33 × 300 = 100