Which benzodiazepine has a half-life of 12 to 15 hours?

• A. Lorazepam
• B. Alprazolam
• C. Diazepam
• D. Midazolam

Answer: (B)

Understanding how long a benzodiazepine stays active helps predict how long its sedative effects will last and whether a patient might feel residual drowsiness the next day. The intermediate-acting option has a typical elimination half-life around 12 to 15 hours, meaning the drug concentration halves roughly every half day and effects persist into the following day but don’t extend for many days.

Alprazolam fits this window best, with a usual half-life in the low tens of hours (about 11–16 hours). That places it in the 12–15 hour range described. In contrast, a long-acting benzodiazepine like diazepam tends to have a much longer half-life due to active metabolites, and midazolam is very short-acting (around 1–4 hours). Lorazepam sits somewhat longer, often cited as about 12–18 hours, which is outside the narrower 12–15 hour range used in this question. So, the drug whose half-life most consistently aligns with 12 to 15 hours is alprazolam.