Benzodiazepines bind to sites on the γ-aminobutyric acid receptor and are cross-tolerant with alcohol and with barbiturates. Four clinical properties: (1) sedative, (2) anxiolytic, (3) skeletal muscle relaxant, and (4) antiepileptic. Individual drugs differ in terms of potency, onset of action, duration of action (related to half-life and presence of active metabolites), and metabolism (Table 200-2). Benzodiazepines have additive effects with alcohol; like alcohol, they can produce tolerance and physiologic dependence, with serious withdrawal syndromes (tremors, seizures, delirium, and autonomic hyperactivity) if discontinued too quickly, especially for those with short half-lives.
|NAME||EQUIVALENT PO DOSE, mg||ONSET OF ACTION||HALF-LIFE, h||COMMENTS|
|Diazepam (Valium)||5||Fast||20–70||Active metabolites; quite sedating|
|Flurazepam (Dalmane)||15||Fast||30–100||Flurazepam is a prodrug; metabolites are active; quite sedating|
|Triazolam (Halcion)||0.25||Intermediate||1.5–5||No active metabolites; can induce confusion and delirium, especially in elderly|
|Lorazepam (Ativan)||1||Intermediate||10–20||No active metabolites; direct hepatic glucuronide conjugation; quite sedating; FDA approved for anxiety with depression|
|Alprazolam (Xanax)||0.5||Intermediate||12–15||Active metabolites; not too sedating; FDA approved for panic disorder and anxiety with depression; tolerance and dependence develop easily; difficult to withdraw|
|Chlordiazepoxide (Librium)||10||Intermediate||5–30||Active metabolites; moderately sedating|
|Oxazepam (Serax)||15||Slow||5–15||No active metabolites; direct glucuronide conjugation; not too sedating|
|Temazepam (Restoril)||15||Slow||9–12||No active metabolites; moderately sedating|
|Clonazepam (Klonopin)||0.5||Slow||18–50||No active metabolites; moderately sedating; FDA approved for panic disorder|
|Clorazepate (Tranxene)||15||Fast||40–200||Low sedation; unreliable absorption|
|Buspirone (BuSpar)||7.5||2 weeks||2–3||Active metabolites; tid dosing—usual daily dose 10–20 mg tid; nonsedating; no additive effects with alcohol; useful for controlling agitation in demented or brain-injured pts|
Buspirone is a nonbenzodiazepine anxiolytic that is nonsedating, is not cross-tolerant with alcohol, and does not induce tolerance or dependence. It requires at least 2 weeks at therapeutic doses to achieve full effects.
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