Following up on last August’s warning that high doses of Celexa can cause potentially fatal heart rhythm abnormalities, the FDA has added clarification to the drug’s label that it should not be used at doses greater than 40 milligrams, and is not recommended for patients with congenital long QT syndrome, bradycardia, hypokalemia, hypomagnesemia, recent heart attack, or uncompensated heart failure. The maximum recommended dose is 20 mg per day for patients with liver impairment, who are older than 60, or patients who take Tagamet of are otherwise impaired metabolizers of CYP 2C19.