| Collection & Request Instructions: | Screening for Tricyclic Antidepressants in human serum or plasma
Tricyclics are widely used for the treatment of depression and also in the treatment of chronic pain. Tricyclic overdoses are sometimes used to try to commit suicide. In this setting, cardiac arrhythmia, respiratory depression and death may result. Despite a change in the epidemiology of intentional antidepressant overdoses Amitriptyline and similar Tricyclics are continuing to be one of the major causes of death in intentional overdose (Sinyor M, Howlett A, Cheung AH, Schaffer A. Substances used in completed suicide by overdose in Toronto: an observational study of coroner's data. Can J Psychiatry. 2012 Mar;57(3):184-91, Gallagher LM, Kappatos D, Tisch C, Ellis PM. Suicide by poisoning in New Zealand--a toxicological analysis. N Z Med J. 2012 Sep 21;125(1362):15-25). With levels greater than 500mg/L the incident of serious cardiac toxicity increases significantly (Simpson GM, Pi EH, White K. Plasma drug levels and clinical response to antidepressants. J Clin Psychiatry. 1983 May;44(5 Pt 2):27-34).
The Abbott Alinity Tricyclic Antidepressant assay (TCA) detects a number of tricyclics such as Amitriptyline, Chlorpromazine, Cyclobenzaprine, Desimipramine, Doxepin, Imipramine and Protriptyline. Different drugs are detected by this method to a varying degree. After consultation Clinical Biochemistry has decided that TCA results are reported as Detected for TCA levels that are greater than 300mg/L (based on nortriptyline). A Detected result in this assay indicates only the presence of a Tricyclic and does not necessarily correlate with the extent of physiological or psychological effects. If clinically indicated, Detected results should be confirmed by more specific methods such as HPLC or LC Tandem MS.
Hans Schneider |
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