TUESDAY, Aug. 2 (HealthDay News) -- New research suggests that hugely popular antidepressants such as Prozac and Effexor might not always be the best choice for seniors, since they seem to have more side effects than older antidepressants do.

Prozac (fluoxetine) and Effexor (venlafaxine) belong to the class of drugs known as selective serotonin reuptake inhibitors (SSRIs), and are generally considered safe and effective. But a new British study appearing in the Aug. 2 issue of the BMJ finds that an older group of drugs known as tricyclic antidepressants may sometimes be safer in people over the age of 65.

Still, several factors need to be considered when choosing an antidepressant, possible side effects being just one of them.

"The choice of class of antidepressant is a complex decision, and some evidence is still lacking to help with that choice in older patients," said study author Carol Coupland, associate professor of medical statistics at the University of Nottingham. "Low-dose [tricyclic antidepressants] may be more suitable in frail elderly patients at increased risk of falls and fracture."

Although SSRIs (which also include Celexa, Paxil and Zoloft) are widely prescribed for depression in seniors, few trials have actually looked at the safety and effectiveness of these drugs in this group of people, added Angie Hochhalter, an assistant professor of internal medicine atTexas A&M Health Science Center College of Medicine.

"We don't find out how the drugs actually work [for seniors] until they've been out for a while," noted Hochhalter, who is also a research scientist in geriatrics at Scott & White in Temple. She was not involved in the new research.

In the study, Coupland's team looked at prescription data on more than 60,000 patients aged 65 to 100 who had been newly diagnosed with depression.

Ninety percent of patients had received one or more prescriptions for antidepressants, 55 percent of those for an SSRI and 32 percent for a tricyclic antidepressant. The rest were on other antidepressants.

Seniors on SSRIs had a higher risk of dying, having a stroke, falling, breaking a bone and seizures compared with those not taking any antidepressant.

Over the course of a year, 10.6 percent of seniors taking an SSRI died vs. 8 percent of those taking tricyclics and 7 percent of those taking no antidepressant at all.

More than 11 percent of those taking other antidepressants died.

Looking at particular antidepressants, Effexor an SSRI, and two tetracyclic drugs, Remeron (mirtazapine) and Desyrel (trazodone), showed the highest risks.

The researchers also noted that the risks were highest in the month after starting an antidepressant and the month after discontinuing the drug.

There was one important limitation to the findings -- tricyclics tended to be prescribed at lower doses than SSRIs, which "can explain at least some of our findings of lower risks associated with [tricyclics]," said Coupland. She added, however, that "there is some evidence from other studies that low-dose [tricyclics] may be as effective as higher doses in reducing symptoms of depression."

This study did not look at the relative effectiveness of the drugs, nor did it look at people who had already been taking SSRIs for years or even decades, Hochhalter pointed out.

The message here is certainly not to avoid SSRIs at all costs, Hochhalter warned.

"When you find the right medication, it can be a lifesaver. But it's so complicated, seniors need to have an ongoing conversation with their doctors," Hochhalter said.

And, added Coupland, "careful monitoring is needed, particularly during the first month of treatment, whichever class is prescribed."

More information

The U.S. National Institutes of Health has more on depression in older adults.