Diazepam has a half-life range of which of the following?

• A. 2-6 hours
• B. 0.12-0.25 hours
• C. 20-50 hours
• D. 10.5-12.9 hours

Answer: (C)

Diazepam has a long elimination half-life, reflecting its pharmacokinetic profile as a long-acting benzodiazepine. In healthy adults, the drug itself typically shows a half-life of about 20 to 50 hours, and its active metabolite desmethyldiazepam can extend the overall duration even further, sometimes contributing to effects that persist into days. Its high lipid solubility causes it to distribute into fatty tissues and be released slowly, which promotes accumulation with repeated dosing and longer-lasting sedation. This combination explains why diazepam remains active for a prolonged period compared with shorter-acting benzodiazepines. The other ranges described do not fit diazepam’s known half-life, since they correspond to much shorter durations.