Nearly one in five patients taking these drugs had longer QT intervals, the study found. Whether this effect is clinically significant, however, isn't known.
"For people who need to take antidepressant doses higher than 40 milligrams of citalopram, there are a number of safe alternatives," Perlis said.
Other antidepressants were not associated with longer QT intervals. In one case, the opposite occurred.
"To our surprise, we also found that another antidepressant, bupropion (Wellbutrin, Zyban), actually shortens QT interval, though we don't know whether this is beneficial or just another indication that it is safe from a cardiac perspective," he said.
In the study, the researchers took other risk factors into account, such as age, race, sex, history of depression, heart attack, high blood pressure, heart rhythm problems and pre-existing conditions. They included methadone because it is also known to cause a longer QT interval.
At least one expert was unconcerned by the study results. "These findings are not surprising and, frankly, not very meaningful," said Dr. Peter Manu, director of medical services at Zucker Hillside Hospital in Glen Oaks, N.Y.
Manu noted that QT interval has to be longer than 500 milliseconds to be a potential problem.
"That occurrence in patients on antidepressants is extraordinarily unusual," Manu said. "In treating more than 30,000 patients over 20 years in this psychiatric hospital, I haven't seen it yet with these medications."
Other factors need to be taken into account to asses risk, Manu added. Most important is whether the patient has an existing heart problem.
"If the person's heart is normal, [longer QT interval] is meaningless," Manu said. "Nobody gets into trouble ever."
If there are underlying h
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