Which class has a T1/2 range of 16-80 hours?

• A. Tricyclics
• B. SSRI/SNRI
• C. Benzodiazepines
• D. Non-Benzo Hypnotics

Answer: (A)

Understanding how long a drug stays in the body helps explain why certain antidepressants require different dosing considerations. Tricyclic antidepressants have notably long and variable half-lives because they are extensively metabolized by the liver and often form active metabolites. This leads to a T1/2 that can span roughly from 16 up to 80 hours, depending on the specific drug and individual differences in metabolism.

This wide range is less typical for the other classes. Non-benzo hypnotics tend to have short half-lives—measured in hours—to minimize next-day sedation. SSRIs and SNRIs generally cluster around a day or more, with some values in the 1–3 day range (fluoxetine being a notable exception with a longer duration). Benzodiazepines show a broad range as well, but their typical patterns don’t define a single broad 16–80 hour span across the whole class like tricyclics do.

So the broad and variable 16–80 hour half-life is characteristic of tricyclic antidepressants, reflecting their metabolism and active metabolites.