Questions: A doctor prescribes ampicillin 40 mg / kg to a patient weighing 55 lbs. Ampicillin is available as 500 mg tablets. How many tablets should the nurse administer?

Solution Steps

To convert the patient's weight from pounds to kilograms, we use the conversion factor $1 \text{ lb} = 0.453592 \text{ kg}$. Thus, the weight in kilograms is calculated as: $$\text{weight}_{\text{kg}} = 55 \text{ lbs} \times 0.453592 \text{ kg/lb} \approx 24.94756 \text{ kg}$$

The prescribed dosage of ampicillin is $40 \text{ mg/kg}$. Therefore, the total dosage required in milligrams is given by: $$\text{total dosage}_{\text{mg}} = \text{weight}_{\text{kg}} \times 40 \text{ mg/kg} \approx 24.94756 \text{ kg} \times 40 \text{ mg/kg} \approx 997.9024 \text{ mg}$$

Ampicillin is available in 500 mg tablets. To find the number of tablets required, we divide the total dosage by the dosage per tablet: $$\text{num tablets} = \frac{\text{total dosage}_{\text{mg}}}{500 \text{ mg}} \approx \frac{997.9024 \text{ mg}}{500 \text{ mg}} \approx 1.9958048$$ Since the nurse cannot administer a fraction of a tablet, we round up to the nearest whole number, resulting in: $$\text{num tablets rounded} = 2$$

Final Answer