Fried’s Rule Calculator

Fried's Rule Calculator

For infants ≤12 months old or 1 Year

Age (months)

Adult Dose

Concentration (mg/mL)

How to Use Fried’s Rule Calculator

Enter the Child’s Age

Input the infant’s age in months (must be between 1-12 months).
Example: 6 months.

Enter the Adult Dose

Type the standard adult dose of the medication.
Example: 500 (for 500 mg or 500 mL).

Select the Unit (mg or mL)

Choose mg (milligrams) if the dose is in weight.
Choose mL (milliliters) if the dose is in volume.

If you select mL, an extra field appears:

Enter Medication Concentration (e.g., 100 mg/mL).

Click “Calculate”

The calculator will display:
- Pediatric Dose (in mg or mL).
- Detailed Calculation Steps (formula breakdown).

What is Fried’s Rule

Fried’s Rule is a pediatric dosing formula used to calculate medication doses for infants under 1 year old. It is based on the infant’s age in months and the adult dose.

Fried’s Rule Formula

This calculation assumes that 150 months (or 12.5 years) represents the standard age at which a child can safely receive the full adult dose. By proportionally adjusting the dose according to the infant’s age in months, Fried’s Rule aims to provide a safer medication quantity for infants whose bodies cannot yet metabolize drugs like adults. Although modern pediatric dosing often uses weight (mg/kg), Fried’s Rule remains an important educational tool for pharmacy students, especially in historical or exam contexts.

History of Fried’s Rule:

Fried’s Rule was developed by German physician Dr. Fried in the 19th century as one of the earliest attempts to calculate pediatric doses of medications. At a time when standardized pediatric dosing was lacking, Fried’s Rule provided a simple, age-based formula specifically for infants under 1 year old. While modern dosing now often relies on weight and body surface area, Fried’s Rule played a foundational role in the evolution of pediatric pharmacology and remains a relevant topic for pharmacy education and exam preparation.

Limitations of Fried’s Rule:

Age Restriction: Only applicable for infants under 1 year (up to 12 months). Not suitable for older children.
Weight Ignored: It does not consider the infant’s weight, which can vary widely and affect drug metabolism.
Assumes Linear Scaling: Assumes that infant dosing is a straight fraction of adult dose, which may not reflect pharmacokinetics accurately.
Risk of Inaccuracy: Can lead to over- or under-dosing if used inappropriately or if the adult dose is not well-established for the medication.
Obsolete in Some Contexts: Modern pediatric dosing usually favors weight-based or body surface area (BSA) methods for greater precision.

Questions and Answers on fried’s Rule

Question 1: For which age group is Fried’s Rule most appropriate?

A. Newborns only
B. Children aged 1–12 years
C. Infants under 1 year of age
D. Adolescents

Answer: C. Infants under 1 year of age

Explanation:
Fried’s Rule was specifically designed for infants under 12 months old. For children older than 1 year, Young’s Rule or Clark’s Rule is more appropriate.

Question 2: Which of the following is a limitation of using Fried’s Rule for pediatric dosing?

A. It uses body weight for calculations
B. It is accurate for children older than 2 years
C. It can be used for all pediatric age groups
D. It ignores the child’s weight and only uses age in months

Correct Answer: D. It ignores the child’s weight and only uses age in months

Explanation:
Fried’s Rule calculates doses based only on age in months, not weight. This can cause dosing inaccuracies, especially if the child is significantly under- or overweight for age.

Question 3: A 6-month-old infant needs a medication that has an adult dose of 120 mg. What is the appropriate dose using Fried’s Rule?

A. 30 mg
B. 60 mg
C. 80 mg
D. 100 mg

Correct Answer: B. 60 mg

Explanation:
Fried’s Rule:(6/150) x 120 = 0.04 x 120 = 60mg

Fried’s Rule Calculator