ANXIOLYTICS

ANXIOLYTICS is a topic covered in the Harrison's Manual of Medicine.

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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.

TABLE 200-2: Anxiolytics
NAMEEQUIVALENT PO DOSE, mgONSET OF ACTIONHALF-LIFE, hCOMMENTS
Benzodiazepines
 Diazepam (Valium)5Fast20–70Active metabolites; quite sedating
 Flurazepam (Dalmane)15Fast30–100Flurazepam is a prodrug; metabolites are active; quite sedating
 Triazolam (Halcion)0.25Intermediate1.5–5No active metabolites; can induce confusion and delirium, especially in elderly
 Lorazepam (Ativan)1Intermediate10–20No active metabolites; direct hepatic glucuronide conjugation; quite sedating; FDA approved for anxiety with depression
 Alprazolam (Xanax)0.5Intermediate12–15Active metabolites; not too sedating; FDA approved for panic disorder and anxiety with depression; tolerance and dependence develop easily; difficult to withdraw
 Chlordiazepoxide (Librium)10Intermediate5–30Active metabolites; moderately sedating
 Oxazepam (Serax)15Slow5–15No active metabolites; direct glucuronide conjugation; not too sedating
 Temazepam (Restoril)15Slow9–12No active metabolites; moderately sedating
 Clonazepam (Klonopin)0.5Slow18–50No active metabolites; moderately sedating; FDA approved for panic disorder
 Clorazepate (Tranxene)15Fast40–200Low sedation; unreliable absorption
Nonbenzodiazepines
 Buspirone (BuSpar)7.52 weeks2–3Active 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
Abbreviation: FDA, U.S. Food and Drug Administration.

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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