Adjustment of Dosages in Pediatric Patients

In general, pediatric patients cannot be given adult dosages of drug. The primary reason for this is the difference in body size. While the drugs discussed in this course provide the drug dosage for pediatric patients, the clinician may be faced with the need to prescribe a drug not listed that does not provide that information. Several rules exist to compute the dosage of a drug for a child, the most common Clark’s Rule. Clark’s Rule determines the dose suitable for a child based on the typical adult weight of 150 lb (or 70 kg). Clarks Rule:

Child’s weight lb (or kg) X adult dose = child’s dose

150 lb (or 70 kg)

For example, if the adult dose of Penicillin VK is 500 mg every 6 hours, the dose for a 40 lb (18 kg) pediatric patient would be calculated as:

40 lb (18 kg) X 500 mg = 133 mg every 6 hours

150 lb (or 70 kg)

Clark’s rule may also be used to calculate dosages for underweight, ill or elderly patients.1