Disclaimer: I am not a medical professional. The following is based on my personal experience and research. Please consult with your healthcare provider before making any changes to your medication.

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Diltiazem (Cardizem) is a popular cardiac medication to treat to treat high blood pressure, angina, supraventricular tachycardia (SVT), and certain heart arrhythmias. It is part of a class of drugs call calcium channel blockers. Listed side effects do not officially include anxiety, depression, or brain fog.

I experienced all three of those and wanted to leave a trail on Google for anyone else experiencing these obscure side effects from diltiazem (Cardizem).

In 2022 I finally got Covid and it brought on moderately bad SVT — my heart wouldn’t stay at an appropriately low heart rate which kept me from recovering. I was already on 120mg/day diltiazem for SVT and my prescription was upped to 360mg/day. The higher dose effectively took care of my SVT but I still struggled with fatigue, brain fog and increased anxiety. All of which I chalked up to long Covid.

After several months of getting back into shape I began to experience bradycardia so I began to taper off of the diltiazem. Immedietly, my fatigue, anxiety and brain fog began to abate. It took me about 6 months to get all the way off of the diltiazem, but with each taper each side effect got even better. It was a one-to-one change me for me. Decrease diltiazem, decrease brain fog, fatigue and depression.

In retrospect, I think that many of the symptoms I attributed to long Covid were from the diltiazem instead.

Research

My research found an article from the 1980’s that described my experience:

None the less, we believe that these case reports show that diltiazem can cause depression. Cases 1 and 5 suggest that
depression caused by diltiazem can be severe and may be accompanied by other symptoms. The latency of onset in these cases ranged from less than a day to one to two months. There was a positive rechallenge in two cases.2 In five of the eight cases the daily dose was 180 mg or more, and the pattern in case 4 suggested a dose related effect.

There are other studies that suggest a link between diltiazem and/or other calcium channel blockers and depression¹:

Although some of those have been critiqued or rebutted by other studies, however, the critiques themselves have limitations.²

Another set of studies looked at using calcium channel blockers to treat depression, especially bipolar disorders.³

The Takaeway for You

If you find yourself with depression, anxiety or other symptoms after starting diltiazem or another calcium channel blocker, you’re not crazy and not alone. Especially if you live with a mood disorder, a calcium channel blocker may have unknown and unintended side effects.

There may not be enough cases for a study to be statistically significant, but that doesn’t mean you shouldn’t advocate for yourself and try another drug. There is no shortage of cardiac medications.⁴

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1. Hullet FJ, Potkin SG, Levy AB, Ciasca R. Depression associated with nifedipine-induced calcium channel blockade. Am J Psychiatry. 1988;145:1277–1279. [PubMed] [Google Scholar]
   
   Dassylva B. Verapamil may cause depression. Can J Psychiatry. 1993;38:299–300. [PubMed] [Google Scholar]
   Hallas J. Evidence of depression provoked by cardiovascular medication: a prescription sequence symmetry analysis. Epidemiology. 1996;7:478–484. [PubMed] [Google Scholar]
   
   Lindberg G, Bingefors K, Ranstam J, Råstam L, Melander A. Use of calcium channel blockers and risk of suicide: ecological findings confirmed in population based cohort study. BMJ. 1998;316:741–745. . (7 March.) [PMC free article] [PubMed] [Google Scholar]
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2. Namely, they are critquing studies that are epimological in nature, which focus on suicide as a result. Observational studies, which are not as robust, are nonetheless not suspeciticble to the same critiques.
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3. This first one is a systematic review and a good source of studies.
   
   Cipriani, A., Saunders, K., Attenburrow, MJ. et al. A systematic review of calcium channel antagonists in bipolar disorder and some considerations for their future development. Mol Psychiatry 21, 1324–1332 (2016). https://doi.org/10.1038/mp.2016.86 [Nature]
   
   Mallinger AG, Thase ME, Haskett R, Buttenfield J, Luckenbaugh DA, Frank E, Kupfer DJ, Manji HK. Verapamil augmentation of lithium treatment improves outcome in mania unresponsive to lithium alone: preliminary findings and a discussion of therapeutic mechanisms. Bipolar Disord. 2008 Dec;10(8):856-66. doi: 10.1111/j.1399-5618.2008.00636.x. PMID: 19594501; PMCID: PMC3387673. [PubMed]
   
   Sarfati Y, Spadone C, Vanelle JM, Lôo H. Inhibiteurs calciques et lithium dans le traitement prophylactique de la maladie maniaco-dépressive [Calcium antagonists and lithium in preventive treatment of manic-depressive disorder]. Encephale. 1996 Mar-Apr;22(2):149-53. French. PMID: 8706625. [Abstract at PubMed]
   
   Levy, N.A. and Janicak, P.G. (2000), Calcium channel antagonists for the treatment of bipolar disorder. Bipolar Disorders, 2: 108-119. https://doi.org/10.1034/j.1399-5618.2000.020204.x
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4. There are entire other classes of cardiac medications. Beta blockers may be an appropriate class of drugs for you to look at if calcium channel blockers appear to cause side effects for you. ↩︎