Selected Tricyclic Antidepressants/Quinidine; Thioridazine Interactions
This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.
Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
Quinidine or thioridazine may slow down how quickly your body processes medicines in the tricyclic antidepressant family: amitriptyline, clomipramine, desipramine, doxepin, imipramine or nortriptyline.
What might happen:
The blood levels of your tricyclic medicine may increase and could cause side effects.
What you should do about this interaction:
Make sure your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together. If you experience weakness, tiredness, dizziness, light headedness, irregular heartbeat, confusion, nervousness, difficulty sleeping, blurred vision, severe constipation, or problems urinating, contact your doctor as soon as possible. It may be necessary to adjust the dose or change one of your medicines.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
- 1.Thioridazine tablet, US prescribing information. Mutual Pharmaceutical September, 2014.
- 2.Salih IS, Thanacoody RH, McKay GA, Thomas SH. Comparison of the effects of thioridazine and mesoridazine on the QT interval in healthy adults after single oral doses. Clin Pharmacol Ther 2007 Nov;82(5):548-54.
- 3.Thanacoody RH, Daly AK, Reilly JG, Ferrier IN, Thomas SH. Factors affecting drug concentrations and QT interval during thioridazine therapy. Clin Pharmacol Ther 2007 Nov;82(5):555-65.
- 4.US Food and Drug Administration (FDA). Drug Development and Drug Interactions: Table of Substrates, Inhibitors and Inducers. Available at: https://www.fda.gov/drugs/drug-interactions-labeling/drug-development-and- drug-interactions-table-substrates-inhibitors-and-inducers. Updated 11/14/2017.
- 5.LLerena A, Berecz R, de la Rubia A, Fernandez-Salguero P, Dorado P. Effect of thioridazine dosage on the debrisoquine hydroxylation phenotype in psychiatric patients with different CYP2D6 genotypes. Ther Drug Monit 2001 Dec;23(6):616-20.
- 6.Amitriptyline hydrochloride, US prescribing information. Sandoz Inc. January, 2010.
- 7.Drew BJ, Ackerman MJ, Funk M, Gibler WB, Kligfield P, Menon V, Philippides GJ, Roden DM, Zareba W. Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. J Am Coll Cardiol 2010 Mar 2;55(9):934-47.
- 8.Pamelor (nortriptyline hydrochloride) US prescribing information. Mallinckrodt Inc. October, 2012.
- 9.Nuedexta (dextromethorphan hydrobromide and quinidine sulfate) US prescribing information. Avanir Pharmaceuticals June, 2019.
- 10.FDA Drug Approval Package application: 021879. Nuedexta (dextromethorphan hydrobromide and quinidine sulfate), Clinical Pharmacology and Biopharmaceutics Reviews. URL: http://www.accessdata.fda.gov/drugsatfda_docs/nda/2010/021879Orig1s000Cli nPharmR.pdf 10/29/2010.
CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.