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Test ID: CDP Chlordiazepoxide and Metabolite, Serum

Reporting Name

Chlordiazepoxide and metabolite, S

Useful For

Monitoring chlordiazepoxide therapy


Assessing toxicity

Clinical Information

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).


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


Chlordiazepoxide and nordiazepoxide combined concentrations above 5000 ng/mL have been associated with toxicity.

Report Available

2 to 7 days

Day(s) Performed

Monday, Wednesday

Clinical Reference

1. Langman, LJ, Bechtel L, Meier BM, Holstege CP, Clinical toxicology. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:832-887

2. Burtis CA, Ashwood ER, Bruns DE, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. WB Saunders Company; 2011:1109-1188

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

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Specimen Type

Serum Red

Shipping Instructions

Ship specimen in amber vial to protect from light.

Specimen Required

Supplies: Sarstedt 5 mL Aliquot Tube (Amber) (T915)

Collection Container/Tube: Red top

Submission Container/Tube: Amber vial

Specimen Volume: 0.5 mL

Collection Instructions: Centrifuge and aliquot serum into amber vial within 2 hours of collection.

Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 14 days LIGHT PROTECTED
  Frozen  14 days LIGHT PROTECTED
  Ambient  24 hours LIGHT PROTECTED

Reference Values

Therapeutic concentration:

Chlordiazepoxide: 400-3,000 ng/mL

Nordiazepam: 100-500 ng/mL

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


G0480 (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CDP Chlordiazepoxide and metabolite, S 33060-5


Result ID Test Result Name Result LOINC Value
8610 Chlordiazepoxide 3457-9
37321 Nordiazepam 3537-8


If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Neurology Specialty Testing Client Test Request (T732)

-Therapeutics Test Request (T831)

Mayo Clinic Laboratories | Neurology Catalog Additional Information: