How to Calculate Drug Dosage for Child

By Soren Bagley
Drugs dosages can be calculated based on your child's weight.

When administering medications to a child, it is especially important to calculate the dosage accurately. Because children are smaller than adults, even a slight miscalculation in dosage can be harmful. There are two different ways drug dosages can be calculated for children. The first bases its calculations solely on the weight of the child (usually in kilograms). The second bases its calculations on body surface area, which takes into account not only the child's weight but his height. The following method is weight-based.

Determine the child's body weight in kilograms. If you only have the weight in pounds, use the "pound/kilogram converter" found in the resources section. If you prefer to do the conversion manually, the rate is 2.2 lb. = 1 kg.

Determine the recommended daily dosage. This information is usually provided with the medication, or it can be obtained from a pediatric drug handbook. There will be both minimum and maximum recommended dosages. The most common way to express these is mg/kg/day (milligrams per kilogram per day). For example, if administering a drug that has a maximum recommended daily dosage of 10 mg/kg/day, within a 24-hour period, you can safely administer 10 mg of the drug to the child for each kilogram of his body weight.

Determine the number of divided doses that are recommended. The number is simply the number of times the drug will be administered within a 24-hour period.

Determine the size of the tablets the medication comes in. This information should be provided with the medication; if the drug is not being administered in tablet form, skip this step. The size of tablets is most commonly expressed in milligrams.

Determine the minimum recommended daily dosage for the child's body weight. To do this, multiply the number of kilograms that the child weighs by the recommended daily dose obtained in section 1 step 2. For example, if the child weighs 50 kg and the minimum recommended daily dose is 10 mg/kg/day, multiply 50 by 10 to get the minimum number of milligrams that should be administered per day.

Determine the maximum recommended daily dosage for the child's body weight. This is determined in exactly the same way as the minimum recommended dosage. For example, if the child weighs 50 kg and the maximum recommended daily dose is 20 mg/kg/day, multiply 50 by 20 to get the maximum number of milligrams that should be administered per day.

Choose the appropriate amount of medication for the child based on the minimum and maximum daily recommendations. Factors to consider include the severity of the child's illness, the child's age and any potential side-effects of the medication.

Determine the amount of medication to be administered per dose. To do this, divide the amount chosen by the number of divided doses that are recommended per day (the number of divided doses were determined in section 1 step 3). For example, if you know you want to administer 400 mg of medication per day and the recommended number of divided doses is two, divide 400 by two to get the number of milligrams that should be administered per dose.

Determine the number of tablets to be administered per dose by taking the amount of medication to be administered per dose and dividing by the amount of medication contained in a single tablet (section 1 step 4). For example, if the amount of medication per dose is 200 mg and the amount of medication per tablet is 100 mg, divide 200 by 100 to get the number of tablets that should be administered per dose.

Warning

Only a medical professional is qualified to determine safe dosages for prescription medications.

About the Author

Soren Bagley recently graduated from the University of Toledo with a B.A. in English Literature. He has been a professional writer for two years and his work has appeared on a wide variety of internet web sites, including Associated Content.com and Ehow.com.