Analysis of 293 studies that assessed 12 commonly prescribed second-generation antidepressants found no significant differences between drugs for treatment of acute-phase depression, according to a report released by the US Agency for Healthcare Quality Research. The review was conducted by the RTI International-University of North Carolina at Chapel Hill Evidence-based Practice Center.

However, side effects among the drugs varied, causing many patients to try more than one before settling on long-term therapy.

The drugs reviewed were bupropion, citalopram, duloxetine, escitalopram, fluoxetine, fluvoxamine, mirtazapine, nefazodone, paroxetine, sertraline, trazodone and venlafaxine. The studies included randomized controlled trials with active or placebo controls, observational studies and systematic reviews.

“Based on our review of the available research, we found very little difference in the effectiveness of various antidepressants,” said Dr. Gerald Gartlehner, lead author of the report and a research associate at University of North Carolina Sheps Center for Health Services Research.

Despite their similarities, the drugs create different side effects that lead only about 60 percent of patients to respond to an initial treatment regimen, said Linda Lux, an RTI researcher. And, she said, 61 percent of patients in efficacy trials experienced at least one adverse side effect, including constipation, diarrhea, dizziness, headache, insomnia and vomiting.

“Because of the high incidence of side effects, many patients try more than one medication before finding an effective treatment,” Lux said. “Predicting which one will be most effective or best tolerated by any individual is not yet possible.”

“This study highlights the important issue that side effects happen to patients, not doctors, and we need to take them a bit more seriously,” said Dr Howard McLeod, director of the UNC’s Institute for Pharmacogenomics and Individualized Therapy.

Gartlehner and Lux said more research is also needed to determine the effects that dosage and duration of second-generation antidepressant treatment have on efficacy, and to see if efficacy differs in patients who also suffer from anxiety, insomnia, pain or fatigue.

The project was supported by the Agency for Healthcare Quality Research, and is posted on the agency’s Web site: http://www.ahrq.gov.