The Food and Drug Administration is recommending that patients taking the anti-depressant Celexa (citalopram hydrobromide) take no more than 40mg a day.

The FDA says anything more can cause abnormal heart rhythms, and studies show there is no therapeutic benefit with doses higher than 40mg. The recommendation includes generic versions of the drug.

Celexa, is made by Forest Laboratories Inc., and is in a class of drugs called selective serotonin reuptake inhibitors (SSRIs). Serotonin is a neurotransmitter-it helps relay messages from one part of the brain to another. Researchers believe serotonin imbalances can influence your mood and lead to depression. SSRIs like Celexa increase the amount of serotonin in the brain, which can help improve mood.

Although the drug is available in 10mg, 20mg and 40mg pills, 60mg doses can be used to treat certain patients with depression.

“Most patients are treated with lower doses of Celexa,” Sandy Walsh, FDA spokesperson said. “But we issued the safety communication today [Wednesday] to make sure doctors and patients have the most up to date information possible to make treatment decisions.”

The FDA says at-risk patients include “those with underlying heart conditions and those who tend to have low levels of potassium and magnesium in their blood.”

The safety announcement warns doctors not to prescribe the drug for patients with congenital long QT syndrome (LQTS)-a condition of the heart’s electrical system that can lead to cardiac arrest or sudden death. LQTS is rare-only about 1 in 5,000 Americans have the condition.

Patients, the agency says, should not stop taking Celexa or change their dose without first talking to their doctor. Stopping suddenly can cause side effects. Any patient who has shortness of breath, irregular heartbeat or dizziness while taking the medication should see their doctor.

Copyright CNN 2011