500 mg of a drug (Molecular weight 100) was intravenously injected into an individual having a blood volume of 5 liter. The drug is neither absorbed…
500 mg of a drug (Molecular weight 100) was intravenously injected into an individual having a blood volume of 5 liter. The drug is neither absorbed by the tissues nor it is excreted. If the drug is metabolized so that half of it is degraded in eight hours, what would be the molar concentration of the drug one day after injection?
Select an option to attempt
Correct Answer: Option C
Explanation
Step-by-step pharmacokinetics calculation:1. Moles of drug injected: 500 mg ÷ 100 g/mol = 5 mmol2. Initial concentration in 5 L blood: 5 mmol ÷ 5 L = 1 mM3. Half-life = 8 hours, so the decay follows:4. At t = 24 hours: number of half-lives = 24 ÷ 8 = 35. Concentration =Note: The answer key indicates 0.625 mM (option 3), which corresponds to only 2 half-lives (16 hours). There is a discrepancy in the question — the exact answer depends on interpretation of 'one day'. The official answer key selects option 3 (0.625 mM).