Pediatric Patients

Pediatric drug therapy presents a unique challenge to clinicians. Often there is a paucity of specific pharmacokinetic and pharmacodynamic data for the pediatric population. Dosage forms designed with the adult population in mind and the dosages cannot easily be individualized for children. Even when appropriate dosage forms for children are available palatability, resistance to taking medications and adherence issues may hinder optimal therapy.

Although there are many rules and formulae to calculate drug dosages for children, weight-based dosing recommendations by manufacturers provide the most reasonable approach.6 Information on a specific drug prescribed to a child can be found in the “Dosage and Administration,” “Contraindications,” “Warning and Precautions” and “Adverse Effects” sections; and in the “Pediatric use” subsection of the drug’s labeling.3

The maximum safe dose of a drug should be carefully calculated for each child. For example, if the MRD of lidocaine, 2% with epinephrine 1:100,000, is 3.2 mg/lb, the maximum safe dose for a child of 25 lbs in milligrams, milliliters, and cartridges would be as follows:

Step 1 – MRD in mg

MRD in mg/lb x weight of patient in lbs = Total MRD in mg
i.e., 3.2 mg/lb x 25 lbs = 80 mg

Step 2 – MRD in ml

Total MRD in mg ÷ mg per ml = Total MRD in ml
i.e., 80 mg ÷ 20 mg/ml (in a 2% formulation) = 4.0 ml

Step 3 – MRD in cartridges

Total MRD in mg ÷ mg/cartridge = Total MRD in cartridges
i.e., 80 mg ÷ 36 mg/cartridge (in a 1.8 cc cartridge) = 2.22 cartridges

Similarly, if the MRD of mepivacaine, 3% plain, is 3 mg/lb, the maximum safe dose for a child of 25 lb in milligrams, milliliters, and cartridges would be as follows:

Step 1 – MRD in mg

MRD in mg/lb x weight of patient in lbs = Total MRD in mg
i.e., 3 mg/lb x 25 lbs = 75 mg

Step 2 – MRD in ml

Total MRD in mg ÷ mg per ml = Total MRD in ml
i.e., 75 mg ÷ 30 mg/ml (in a 3% formulation) = 2.5 ml

Step 3 – MRD in cartridges

Total MRD in mg ÷ mg per cartridge = Total MRD in cartridges
i.e., 75 mg ÷ 54 (in a 1.8 cc cartridge) = 1.38 cartridges