Because clinical depression is so disabling and affects more than 16 percent of adults in the United States at some time in their lives, researchers have worked hard to develop more effective treatments. But how much better are the newer pharmaceuticals?
Many second-generation antidepressants, despite differences in drug classification and cost, offer patients essentially the same benefits with little variation in risks, University of North Carolina at Chapel Hill researchers have found.
Such antidepressants include selective serotonin reuptake inhibitors (SSRIs) and other drugs that affect the activity of neurotransmitters in a selective way.
In a paper published online today (Sept. 19) and to be published in the October issue of the journal Annals of Internal Medicine, Dr. Richard A. Hansen and colleagues examined the effects of 10 commonly prescribed second-generation antidepressants. Those drugs included familiar brand-name drugs such as Prozac, Zoloft, Effexor, Wellbutrin and Paxil.
Hansen is assistant professor of pharmacy at the UNC School of Pharmacy. The study he led involved investigating the medications' role in the initial treatment of adults suffering from major depression by combining and systematically analyzing data from 46 randomized, controlled trials.
Other authors, all at UNC, are Drs. Gerald Gartlehner and Timothy S. Carey of the Cecil G. Sheps Center for Health Services Research, Dr. Kathleen N. Lohr of the health policy and administration department at the School of Public Health, and Bradley N. Gaynes of the School of Medicine's psychiatry department. Carey, professor of medicine, directs the Sheps Center. Gartlehner is associate director of the RTI-UNC Evidence-based Practice Center.
"Past studies have compared the effectiveness of second-generation antidepressants with that of placebo or older treatments but have not systematically evaluated how the second-generation agents compared to each other," Hansen said. "Given the number of second-generation treatments available, cost differences, widespread use and the general lack of consensus in how the drugs compare, our research can help patients, clinicians and policy makers decide which drug is best."
The bottom line was that one was about as good as another in terms of effectiveness, but the likelihood that patients experienced certain side effects differed between compounds, he said.
"Comparative evidence on these drugs suggests that there are only minimal differences in efficacy, although some of the drugs come with an increased risk of certain side effects," Hansen said. "Understanding the likelihood of the side effects and matching this information with patients' lifestyle and preferences for anticipated side effects may help improve drug treatment of depression.
"Although our study did not specifically assess the impact of drug costs or differences in dosing regimens on how patients fared, those factors also may be important determinants in drug selection," the scientist said. "That's in the absence of patient preference or a clear choice for which agent is best for a given person."
Limitations of the study were that published data from some trials was not as complete and comparable as researchers would have preferred, Hansen said. Most data was from trials sponsored by drug companies, and questions remain as to how unbiased such studies are.
Support for the investigation came to the Cecil G. Sheps Center for Health Services Research from the Drug Effectiveness Review Project, a collaborative program coordinated by the Center for Evidence-Based Policy at the Oregon Health and Science University.
In 2000, the economic burden of depression was estimated to be $83.1 billion, Hansen said. Although drug treatment does not work for all patients, drugs are usually considered the first and potentially best treatment in part since primary care physicians prescribe the majority of antidepressants in this country.