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Test Catalog

Test ID: CDP    
Chlordiazepoxide and Metabolite, Serum

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

Monitoring chlordiazepoxide therapy


Assessing toxicity


Because chlordiazepoxide has a wide therapeutic index and dose-dependent toxicity, routine drug monitoring is not indicated in all patients

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

Chlordiazepoxide (Librium) is a benzodiazepine widely used in the treatment of anxiety, alcohol withdrawal symptoms, and as a premedication for anesthesia. The mechanism of action of all benzodiazepines remains unclear. However, it is known that benzodiazepines facilitate gamma-amino butyric acid (GABA)-mediated neurotransmission in the brain. Benzodiazepines most likely facilitate the inhibitory presynaptic or postsynaptic reactions of GABA.


Chlordiazepoxide is metabolized to long-acting metabolites in the liver to the active metabolite nordiazepam (desmethyldiazepam) and the clearance of the drug is reduced considerably in the elderly and in patients with hepatic disease.


Therapeutic assessment should include measurement of both the parent drug (chlordiazepoxide) and the active metabolite (nordiazepam).

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 concentration:

Chlordiazepoxide: 400-3,000 ng/mL

Nordiazepam: 100-500 ng/mL

Interpretation Provides information to assist in interpretation of the test results

A therapeutic dose will yield a serum concentration of 1,000 to 3,000 ng/mL.


Toxic concentration: >5,000 ng/mL

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

The specimen must be protected from light. 

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

1. Langman, LJ, Bechtel L, Holstege CP, Chapter 35: Clinical Toxicology, In Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Edited by CA Burtis, ER Ashwood, DE Bruns. WB Saunders Company, Philadelphia, PA, 2011, pp 1109-1188

2. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, Edited by CA Burtis, ER Ashwood, DE Bruns, WB Saunders Company, Philadelphia, PA, 2011, Table 60.2, pp 1109-1188

3. Hiemke C, Baumann P, Bergemann N, et al: AGNP Consensus Guidelines for Therapeutic Drug Monitoring in Psychiatry: Update 2011. Pharmacopsychiatry 2011;44:195-235