Clark's rule

Clark's Rule is a medical term referring to a procedure used to calculate the amount of medicine to give to a child aged 2-17. The procedure is to take the child's weight in pounds, divide by 150 lb, and multiply the fractional result by the adult dose to find the equivalent child dosage.

For example: If an adult dose of medication calls for 30 mg and the child weighs 30 lb. Divide the weight by 150 (30/150) to get 1/5. Multiply 1/5 times 30 mg to get 6 mg.

Clark's Rule is not used clinically, but it is a popular dosage calculation formula for pediatric nursing instructors.