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Table 8. Pharmacokinetic Properties of Benzodiazepines
Benzodiazepine
Time to peak plasma level
(h; via oral)
Relative lipid solubility
a
Alprazolam 1–2 h (tablet or orally disintegrating
tablet [ODT]) 5–11 h extended release
(XR)
Moderate
Chlordiazepoxide 0.5–4 h Moderate
Clonazepam 1–2 h Low
Clorazepate
e
0.5–2 h High
Diazepam 0.5–2 h High
Estazolam 2 h Low
Flurazepam 0.5–2 h High
Lorazepam 2–4 h Moderate
Oxazepam 2–4 h Low
Quazepam 2 h High
Temazepam 2–3 h Moderate
Triazolam 1–2 h Moderate
a
Increased lipid solubility results in more rapid onset of CNS activity but can also result in
rapid redistribution into adipose tissue resulting in a shorter duration of action even in agents
with long elimination half-life (e.g., diazepam)
b
Rapid onset of action is associated with high lipid solubility and increased potential for misuse.
c
Agents with moderate to high lipid solubility will have shorter duration of action with
single or intermittent doses than suggested by the elimination half-life as these medications
distribute rapidly into adipose tissue. With initial dosing, multiple daily doses may be needed
to maintain effect. With chronic use and repeated dosing, accumulation is more likely to
occur with these agents, especially those with long elimination half-lives (e.g., diazepam).
d
Agents metabolized via glucuronide conjugation do not have pharmacokinetic interactions
and are considered to be safer in older adults and patients with hepatic impairment.
e
Hydrolized to nordiazepam in the stomach.
