Clark's rule is an equation used to calculate pediatric medication dosage based on the known weight of a patient and a known adult dose of medication to be used. Clark's rule equation is defined as the weight of the patient in pounds divided by the average standard weight of 150 pounds (68 kg) multiplied by the adult dose of a drug equals the pediatric medication dose, as is demonstrated below:
- (Weight* divided by 150 lbs.) x Adult Dose** = Pediatric Dosage
- (Weight*** divided by 68 kg) x Adult Dose** = Pediatric Dosage
*Weight of pediatric patient in pounds (lbs.)
**Adult dose is the recommended dosage for adult medication use
***Weight of pediatric patient in kilograms (kg)
Clark's rule is one of the known pediatric medication dosing rules described in the medical literature that utilizes the patient's weight to calculate medication dosage. Other equations that utilize pediatric weight to calculate medication dosing include Salisbury's rule, Penna's rule, and the Body Surface Area rule. Other methods besides Clark's rule that also utilize pediatric age to calculate radiopharmaceutical medication dosages used in nuclear imaging include Young's rule, Webster's rule, and Fried's rule.