A few widely used drugs once again are coming under heated fire, one thanks to the FDA and the other class courtesy of a consumer watchdog organization.

High doses of Celexa, an antidepressant, can cause abnormal heart rhythms, prompting the feds to issue a new warning that it should not be prescribed at doses higher than 40 mg per day. Disrupting the heart’s regular electrical activity can be serious and potentially fatal. Celexa packaging will now include a safety warning.

Available as a brand-name or generic drug, Celexa belongs to the class of antidepressants called selective serotonin reuptake inhibitors (SSRIs), which have been shown to be effective in treating major depression. Doses greater than 40 mg, the FDA says, are not of greater benefit. Sometimes Celexa is prescribed for other psychological disorders, a practice known as “off-label” treatment, so there is no “proper” dosage for such uses.