Pediatric Dose Calculator

Pediatric dosage explained

There are several methods available for estimating pediatric dosages, the most commonly used being dosing according to body weight or body surface area (BSA).

Doses are often expressed as mg/kg/day (similar to mg/kg) or mg/kg/dose and accompanied by a frequency of administration that can vary from once daily to every hour. The above calculations accept mcg/kg/day or mcg/kg/dose as well, to facilitate use.

The following table summarizes the main administration frequencies, as commonly found on prescriptions:

Some medication is available in multiple concentrations, for example a solution of 5mg/10mL. This pediatric dose calculator is also able to compute the quantity of solution to be administered (both daily and per dose), given the pediatric dosage required.

Child doses based on weight

Children tend to me more at risk of medication overdose, toxic reactions, morbidity and mortality given that their physiological processes (e.g. absorption, distribution, metabolism and excretion) are more immature. Typically, hepatic and renal function in young infants presents a slower metabolism and excretion. Once an adolescent attains a weight of 50 kg (appx 110 lbs) or greater, standard adult dosage may be prescribed.

Safe pediatric dosages can be calculated from adult doses based on child’s weight in kilograms. It is important to note whether the dosage starts from the daily dose or the dose per administration.

• Child dose by weight = (mg/day) = Adult Dose in mg/kg or mg/kg/day x Child Weight in kg

OR

• Child dose by weight = (mg/dose) = Adult Dose in mg/kg/dose x Child Weight in kg

Child doses based on BSA

Child doses calculated by weight in some cases may lead to underdosage, whereas, dosages calculated by BSA give a higher value, and a better quality study. After the age of 1 year, organ growth and physiological function conform more accurately to BSA than body weight.

Chemotherapeutic drugs are commonly dosed according to body surface area, method which requires an extra verification step (BSA calculation) prior to dosing. This can be done with the help of the West Nomogram when the child’s height and weight are known.

• Child dose by BSA (mg/day) = Adult Dose in mg/day x BSA in m2 / 1.73

OR (if medicine concentration is known in mg/m²):

• Child dose by BSA (mg/day) = Adult Dose in mg/m2 x BSA in m2

Child doses based on Young’s rule

Young’s rule for pediatric dosage is based on age and approximates the body weight rule except during the first years of life and adolescence. This rule is not to be used in nfants and some consideration must be taken for growth variability at any given age.

• Child dose by Young’s rule (mg/day) = Adult Dose (mg/day) x [Age / (Age+12)]

Child doses based on Clark’s rule

Clark’s rule for pediatric dosage is based on proportional body weights as related to the standard weight mean of 150 pounds. Therefore, for this method, the weight of the child is considered in lbs not kilograms.

• Child dose by Clark’s rule (mg/day) = Adult Dose (mg/day) x (Child Weight in Lbs /150)

Both the Young and Clark’s rule are used in prescribing pediatric radioactivity dosages.

References

Gerald MC, O’Bannon FV. Nursing pharmacology and therapeutics. (2nd ed.). Englewood Cliffs, NJ: Prentice Hall Incorporated, 1988.

Breslow K. The pediatric radiopharmaceutical dose. The Monthly Scan (Radiopharmacy, College of Pharmacy, University of New Mexico); 1979.

Kowalsky RJ, Perry JR. Radiopharmaceuticals in Nuclear Medicine Practice. East Norwalk, CT/Los Altos, CA; Appleton and Lange 1987.

Bell EG, McAfee JG, Subramanian G. Radiopharmaceuticals in pediatrics. In James AE, Wagner HN, Cooke RE, eds. Pediatric Nuclear Medicine. Philadelphia: W.B. Saunders, 1974.