As a hospital or community pharmacist, you will hear about limiting doses of citalopram (Cipram, etc). Experts say citalopram doses should not exceed 40 mg/day for anyone, or 20 mg/day for most patients over age 60. Higher doses of citalopram increase the risk of QT prolongation and the life-threatening arrhythmia, torsades.
Caution about using citalopram in patients at risk due to underlying cardiac disease or low serum potassium or magnesium. Suggest avoiding citalopram or monitoring the ECG if citalopram is used in patients with heart failure, bradyarrhythmias, or on other medications that can prolong the QT interval. Recommend not exceeding citalopram 20 mg in most patients over age 60, or those with liver impairment. Also avoid going over 20 mg/day when combined with CYP2C19 inhibitors (omeprazole, cimetidine, etc).
If these lower doses aren't adequate, recommend switching to another antidepressant. Explain that sertraline, paroxetine, and fluoxetine seem less likely to cause QT prolongation. Caution not to exceed 20 mg/day of escitalopram (Cipralex). Explain that usual doses aren't associated with significant QT prolongation, but the risk increases with higher doses.
REFERENCES
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Research, C. for D.E. and (2021). FDA Drug Safety Communication: Abnormal heart rhythms associated with high doses of Celexa (citalopram hydrobromide). FDA. [online] Available at: https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-abnormal-heart-rhythms-associated-high-doses-celexa-citalopram
Isbister GK, Bowe SJ, Dawson A, Whyte IM. Relative toxicity of selective serotonin reuptake inhibitors (SSRIs) in overdose. J Toxicol Clin Toxicol. 2004;42(3):277-85. Available at: https://www.tandfonline.com/doi/abs/10.1081/CLT-120037428?journalCode=ictx19