A nurse is preparing to administer chlorpromazine 0.55 mg/kg IM every 6 hr to a child who weighs 44 lb. Available is chlorpromazine 25 mg/mL injection. How many mL should the nurse administer per dose? (Round the answer to the nearest tenth. Use a leading zero if it applies. Do not use a trailing zero.)
The Correct answer and explanation is:
To calculate the correct dosage of chlorpromazine that the nurse should administer to a child, we must follow a step-by-step process to ensure accuracy.
Step 1: Convert the child’s weight to kilograms
The child’s weight is given in pounds (44 lb). Since medication dosages are often calculated based on the patient’s weight in kilograms, we need to convert the weight from pounds to kilograms using the conversion factor: 1 lb=0.454 kg1 \text{ lb} = 0.454 \text{ kg}1 lb=0.454 kg 44 lb×0.454=19.96 kg44 \text{ lb} \times 0.454 = 19.96 \text{ kg}44 lb×0.454=19.96 kg We can round the weight to 20 kg for easier calculation.
Step 2: Calculate the required dose in milligrams
The prescribed dose is 0.55 mg/kg. To determine the dose for the child, we multiply the dose by the child’s weight in kilograms: 0.55 mg/kg×20 kg=11 mg0.55 \text{ mg/kg} \times 20 \text{ kg} = 11 \text{ mg}0.55 mg/kg×20 kg=11 mg This means that the child needs 11 mg of chlorpromazine per dose.
Step 3: Determine the volume to administer
The chlorpromazine is available in a concentration of 25 mg/mL. To find out how many milliliters (mL) the nurse should administer, we use the following formula: Volume (mL)=Dose (mg)Concentration (mg/mL)\text{Volume (mL)} = \frac{\text{Dose (mg)}}{\text{Concentration (mg/mL)}}Volume (mL)=Concentration (mg/mL)Dose (mg) Volume (mL)=11 mg25 mg/mL=0.44 mL\text{Volume (mL)} = \frac{11 \text{ mg}}{25 \text{ mg/mL}} = 0.44 \text{ mL}Volume (mL)=25 mg/mL11 mg=0.44 mL
Step 4: Round to the nearest tenth
The calculation yields 0.44 mL. Since the instructions require rounding to the nearest tenth, the correct dosage to administer is: 0.4 mL0.4 \text{ mL}0.4 mL
Final Answer:
The nurse should administer 0.4 mL of chlorpromazine per dose.
Explanation:
When calculating medication dosages, accuracy is crucial. The process begins with converting the patient’s weight to kilograms because dosing in pediatric patients is often weight-based and calculated in mg/kg. After determining the dose, we calculate the volume of the medication using its concentration. Rounding is necessary to match the clinical standards and minimize the risk of dosage errors. Using a leading zero is essential when the dose is less than 1 mL to avoid misinterpretation, and avoiding a trailing zero prevents the risk of administering an incorrect, higher dose. This precise calculation ensures safe and effective medication administration, preventing underdosing or overdosing, which could lead to therapeutic failure or adverse effects.