Test Catalog

Test ID: CLOM    
Clomipramine, Serum

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

Determining whether a poor therapeutic response is attributable to noncompliance


Monitoring serum concentration of clomipramine and norclomipramine to assist in optimizing the administered dose

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

Clomipramine (chlorimipramine, Anafranil) is a tricyclic antidepressant drug used primarily to treat obsessive-compulsive disorder (OCD). Clomipramine is also used to treat panic disorder and treatment-resistant depression.


Clomipramine preferentially blocks synaptic reuptake of serotonin; its pharmacologically active metabolite, norclomipramine (desmethylchlorimipramine) preferentially blocks synaptic reuptake of norepinephrine.


Clomipramine undergoes significant first-pass hepatic metabolism (up to 50%) which probably explains the high degree of interindividual variability observed between administered dose and steady-state serum concentrations of the drug and its metabolite. The serum ratio of clomipramine to norclomipramine is typically 1:2-2.5. The elimination half-lives of clomipramine and norclomipramine are 19-37 hours and 54-77 hours, respectively. One to two weeks are required to achieve steady-state when a patient is started on clomipramine or following an alteration in the dose.


Anticholinergic side effects (ie, dry mouth, excessive sweating, blurred vision, urinary retention, constipation) frequently accompany treatment. Other side effects may include tremor, nausea, orthostatic hypotension, dizziness, sexual dysfunction, and sleep disturbances. Signs and symptoms following overdose are similar to other tricyclic antidepressant drugs: cardiac toxicity (eg, tachycardia, arrhythmia, impaired conduction, congestive heart failure) is the major concern.

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: 230-450 ng/mL


Note: Therapeutic ranges are for specimens drawn at trough (ie, immediately before next scheduled dose). Levels may be elevated in non-trough specimens.

Interpretation Provides information to assist in interpretation of the test results

Studies investigating the relationship between serum concentrations of clomipramine and norclomipramine and therapeutic response have yielded conflicting results. However, the probability of therapeutic failure seems to increase if the sum of the clomipramine and norclomipramine serum concentrations is <230 ng/mL. Summed serum concentrations of clomipramine and norclomipramine which exceed 450 ng/mL seem to result in no additional enhancement in therapeutic response and may predispose the patient to greater risk of adverse side affects. A toxic range has not been well established at this time.

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

This test cannot be performed on whole blood. Serum must be separated from cells within 2 hours of drawing; if serum is not removed within this time, tricyclic antidepressant levels may be falsely elevated due to drug release from RBCs. Specimens that are obtained from gel tubes are also not acceptable, as the drug can absorb on the gel and lead to falsely decreased concentrations.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Wille SM, Cooreman SG, Neels HM, Lambert WE: Relevant issues in the monitoring and the toxicology of antidepressants. Crit Rev Clin Lab Sci 2008;45(1):25-89

2. Thanacoody HK, Thomas SH: Antidepressant poisoning. Clin Med 2003;3(2):114-118

3. Hiemke C, et.al: AGNP Concensus Guidelines for Therapeutic Drug Monitoring in Psychiatry: Update 2011. Pharmacopsychiatry 2011;44(6):195-235

4. Burtis CA, Ashwood ER, Bruns DE. (2012) Tietz Textbook of Clinical Chemistry and Molecular Diagnostics: Fifth Edition, Elsevier