Answer:
Option B, 300 mg/dose
Explanation:
The first step in completing this dosage calculation problem is determining the daily amount of intravenous (IV) antibiotic medication vancomycin the patient is to receiving given their weight in kilograms (kg).
To do so, multiply the patient's weight in kilograms by the ordered amount of medication. The ordered amount is the quantity of medication prescribed to the patient by a provider (typically a physician), usually expressed in mass (e.g. milligrams, mg) but sometimes expressed in a ratio of mass-per-weight. In this case, the ordered amount is 40mg/kg/day, as evidenced by the prompt stating this rate yields the total daily dosage.
22.5 kg × (40 mg / kg/day)
= (22.5 kg × 40 mg) ÷ kg/day
= 900 kg mg ÷ kg/day
kg in both numerator and denominator cancel each other out leaving mg/day as the remaining units
= 900 mg/day
Finally, the individual dosage can be determined by dividing the total daily amount by the frequency of doses. According to the prompt, a dose is to be administered every 8 hours (q8h). There are 24 hours in one day; 24 ÷ 8 = 3; therefore, 900 mg total is to be equally divided into 3 doses.
900 mg ÷ 3 doses
= 300 mg/dose
The patient should be administered 300 mg/dose, option B, of antibiotic medication vancomycin IV.