Anxiety Disorders: Description and Etiology
Table 4. Commonly Prescribed Benzodiazepines in Cancer Patientsa
bid = twice a day; qd = once a day; qid = 4 times a day; tid = 3 times a day.
a Adapted from Breitbart et al.
b Refer to the PDQ summary on Depression for dosing information on antidepressants used for anxiety as described in this summary.
|Drug Equivalent ||Approximate Oral Dose (mg)b||Initial Dose (mg)||Elimination Half-life of Drug Metabolites (h)|
|Alprazolam (Xanax)||0.5||0.25-2.0 tid-qid||10-15|
|Oxazepam (Serax)||10.5||10-15 tid-qid||5-15|
|Lorazepam (Ativan)||1.0||0.5-2.0 tid-qid||10-20|
|Temazepam (Restoril)||15.0||15-30 at bedtime||10-15|
|Alprazolam (Xanax XR)|| 1.0||1-6 qd||10-15|
|Clonazepam (Klonopin)||1.0||0.5-2.0 bid-tid||19-50|
|Chlordiazepoxide (Librium)||10.0 ||10-50 tid-qid||10-40|
|Diazepam (Valium)||5.0||5-10 bid-qid||20-100|
|Clorazepate (Tranxene)||7.5 ||7.5-15.0 bid||30-200|
The choice of a benzodiazepine depends on the following:
- Duration of action that is best suited to the patient.
- Desired rapidity of onset needed.
- Route of administration available.
- Presence or absence of active metabolites.
- Metabolic problems.
Dosing schedules depend on patient tolerance and require individual titration. The shorter-acting benzodiazepines (alprazolam and lorazepam) are given 3 to 4 times per day. Short-acting benzodiazepines, particularly those that can be administered by multiple routes (lorazepam and diazepam), are effective for high levels of distress. Benzodiazepines decrease daytime anxiety and reduce insomnia. (Refer to the PDQ summary on Sleep Disorders for more information.) The most common side effects of benzodiazepines are dose dependent and are controlled by titrating the dose to avoid drowsiness, confusion, motor incoordination, and sedation.
All benzodiazepines can cause some degree of respiratory depression, which is generally minimal in patients who have not used benzodiazepines in the past. Benzodiazepines should be used cautiously (or not at all) in cases of respiratory impairment.
Standard precautions should be considered when any sedative drug is used in patients who have borderline respiratory function. Ongoing assessment of this population is important. Low doses of the antihistamine hydroxyzine (25 mg, 2-3 times a day) can be used safely in such situations. In patients with hepatic dysfunction, it is best to use short-acting benzodiazepines that are metabolized primarily by conjugation and excreted by the kidneys (e.g., oxazepam, temazepam, or lorazepam). Another advantage of using lorazepam is its lack of active metabolites. Conversely, other benzodiazepines should be selected in cases of renal dysfunction.
SSRIs (e.g., fluoxetine and sertraline) and serotonin-norepinephrine reuptake inhibitors (SNRIs) (e.g., venlafaxine) are considered first-line pharmacotherapy for long-term management of anxiety disorders. SSRIs and SNRIs are also effective in the treatment of depressive symptoms frequently comorbid with persistent anxiety disorders. SSRIs and SNRIs can take approximately 4 to 6 weeks to take effect because of their slow onset of action. Benzodiazepines are frequently used as adjunctive agents to stabilize symptoms in the initial period of treatment with SSRIs and SNRIs.