An injection has a ratio strength of 1:500, meaning 1 g of drug is present in 500 mL of solution. How much drug is present in 12 mL?
Correct answer: C. 24 mg
- A. 12 mg
- B. 20 mg
- C. 24 mg
- D. 60 mg
Explanation
One gram equals 1,000 mg, so the concentration is 1,000 mg ÷ 500 mL = 2 mg/mL. In 12 mL, the amount is 12 × 2 = 24 mg. The ratio describes the amount in the whole 500 mL, not in each millilitre.
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About Drug Calculations and Dosage
Drug calculations apply measurement systems, unit conversions, dosage formulas, tablet and liquid doses, percentage and ratio strength, and weight based dosing. Work also includes calculating IV flow rates, infusion times and doses for children, while distinguishing the prescribed dose from the available concentration.
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