Half-life
The time it takes your body to eliminate half of a drug — the single number that best predicts how hard a drug is to stop abruptly.
For psychiatric medications, half-life matters most at the exit.
What it is
A drug's half-life is how long your body takes to clear half of it: after one half-life 50% remains, after five it is effectively gone. Fluoxetine's active forms are measured in days; venlafaxine's in hours.
Why the exit cares
A short-half-life drug leaves the body fast, which is why abrupt stops of venlafaxine, paroxetine and duloxetine run rougher than fluoxetine — the long-half-life drug performs a slow taper on its own even when you stop outright. Half-life also explains why missed doses hit some drugs harder, and why some tapers deliberately switch to a longer-half-life drug before the final stop.
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Questions
Which antidepressants are hardest to stop?
As a class pattern: the short-half-life ones — venlafaxine, paroxetine, duloxetine — are consistently named hardest for abrupt stops. Individual experience varies.
Does a longer half-life mean a better drug?
No — it means different trade-offs: gentler exits, slower washout when you need the drug gone (for example before switching).
Keep reading
More from the glossary
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