A primary healthcare provider has prescribed ertapenem to a 6-year-old child with a urinary tract infection (UTI).
What is the safe dose of medication for this child?

This answer is correct because BSA is the most accurate method for calculating the child's dose from the adult dose¹². BSA takes into account the child's weight and height, and reflects the physiological function and organ growth of the child beter than weight alone¹. BSA can be calculated using a nomogram or a formula based on the child's weight and height¹. The child's dose can then be calculated by multiplying the adult dose by the ratio of the child's BSA to the average adult BSA (1.73 m2)¹. For example:

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

OR

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

The other options are not correct because they are not accurate methods for calculating the child's dose from the adult dose. Actual body weight and ideal body weight may not account for individual variations in pharmacokinetics, pharmacodynamics, or clinical response. Actual body height is not a reliable indicator of drug dosage, as it does not reflect the body mass or organ function of the child.

This answer is correct because it is based on a series of unit conversions and calculations. The nurse should follow these steps to provide safe medication to the child:

1) Convert the child's weight from pounds to kilograms by dividing by 2.2, since there are 2.2 lbs in 1 kg. The child weighs 20 kg.

2) Multiply the prescribed dose per kilogram by the child's weight in kilograms to get the total dose in milligrams. The child needs 40 mg of pyrimethamine.

3) Use the ratio given on the drug label to convert the total dose in milligrams to the volume in milliliters. The nurse can set up a proportion as follows:

1 mg / 5 mL = 40 mg / x mL

Cross-multiplying and solving for x gives:

x = 200 mL

Therefore, the nurse should administer 200 mL of medication to deliver 40 mg of pyrimethamine to the child.

4) Convert the volume in milliliters to the volume in teaspoons by dividing by 5, since there are 5 mL in 1 tsp. The nurse should administer 40 tsp of medication to the child.

5) Convert the volume in teaspoons to the volume in cups by dividing by 48, since there are 48 tsp in 1 cup. The nurse should administer 0.83 cups of medication to the child.