Alprazolam vs Diazepam: what is the difference?

How they differ

Both are benzodiazepines and both work by making the brain's own GABA more effective at its receptor, and the difference between them is timing. Alprazolam acts fast and clears fast, with a half-life around 11 hours, which is why it is associated with acute panic and also with a sharper rebound as it leaves. Diazepam is absorbed very quickly but persists far longer, and it produces long-lived active metabolites including nordazepam that can stretch its effect over days. That is why diazepam is used to taper other benzodiazepines and alprazolam is not. Alprazolam is the more potent per unit weight by a wide margin. Structurally alprazolam carries a triazole ring fused to the benzodiazepine core that diazepam lacks.

Side by side

Structural similarity 0.58 of 1, computed as a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.

Common questions

What is the difference between Alprazolam and Diazepam?

Both are benzodiazepines and both work by making the brain's own GABA more effective at its receptor, and the difference between them is timing. Alprazolam acts fast and clears fast, with a half-life around 11 hours, which is why it is associated with acute panic and also with a sharper rebound as it leaves. Diazepam is absorbed very quickly but persists far longer, and it produces long-lived active metabolites including nordazepam that can stretch its effect over days.

Is Alprazolam bigger than Diazepam?

Alprazolam is the heavier molecule, 308.8 g/mol against 284.74 g/mol for Diazepam. Alprazolam is C17H13ClN4 and Diazepam is C16H13ClN2O.

Which has the lower reported LD50, Alprazolam or Diazepam?

Diazepam, at 710 mg/kg (oral, rat), against 1,220 mg/kg (oral, rat) for Alprazolam. An LD50 is one acute animal measurement, and the two here were not necessarily measured in the same species, so it is a data point rather than a ranking of how dangerous either is to a person.