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Test ID: ALPA    
Alprazolam, Serum              

Useful For Suggests clinical disorders or settings where the test may be helpful

Monitoring patient compliance


Helping to achieve desired blood levels and avoid toxicity

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Alprazolam (Xanax), a drug used to treat panic and anxiety disorders, is a triazolobenzodiazepine with the same ring structures as triazolam. It is considered an intermediate benzodiazepine with a half-life of 6 to 20 hours and a rapid onset of action with peak plasma levels reached within 1 to 2 hours of dosing. Typical daily doses range from 0.75 to 3.0 mg and Xanax tablets are available in 0.25 mg, 0.5 mg, 1 mg, or 2 mg doses.


Hepatic biotransformation of alprazolam produces hydroxylated metabolites, which are excreted in urine as glucuronide metabolites. Alprazolam has 2 major metabolites: alpha-hydroxy-alprazolam and 4-hydroxyalprazolam. A benzophenone derivative is also found in humans. Only the hydroxy-alprazolams are biologically active with approximately one half the activity of the parent drug. Since the metabolites are only present in trace amounts in serum, quantitation of metabolites is not clinically significant.


Alprazolam may have central nervous system (CNS) depressant effects. Patients using alprazolam should avoid other CNS depressant drugs, as well as ingestion of alcohol.


When discontinuing therapy in patients who have used alprazolam for prolonged periods, the dose should be decreased gradually over 4 to 8 weeks to avoid the possibility of withdrawal symptoms, especially in patients with a history of seizures or epilepsy, regardless of their concomitant anticonvulsant drug therapy. Patients on short-acting benzodiazepines may be switched to longer-acting drugs (eg, diazepam), which produce a gradual decrease in drug concentration and decrease the risk of withdrawal symptoms.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Therapeutic range: 5-25 ng/mL

Some patients respond well to levels of 25-55 ng/mL.

Interpretation Provides information to assist in interpretation of the test results

The assessment of treatment with alprazolam should be based on clinical response. Effectiveness of treatment can be determined by the reduction of symptoms of anxiety and panic disorders.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Malseed RT, Harrigan GS: Antianxiety drugs. In Textbook of Pharmacology and Nursing Care. JB Lippincott Company 1989, p 519

2. Fraser AD, Bryan W: Evaluation of the Abbott ADx and TDx serum benzodiazepine immunoassays for analysis of alprazolam. J Anal Toxicol 1991;15:63-65

3. Miller RL, Devane CL: Alprazolam, alpha-hydroxy-and 4-hydroxyalprazolam analysis in plasma by high-performance liquid chromatography. J Chromatogr 1988;430:180-186

4. Labrosse KR, McCoy HG: Reliability of antidepressant assays: a reference laboratory perspective on antidepressant monitoring. Clin Chem 1988;34:859-862

5. Physicians’ Desk Reference (PDR) 2007