"There's a sense that we need something else for elderly patients and here is an alternative that is well tolerated," said Alan Schatzberg, MD, the Kenneth T. Norris, Jr. Professor of Psychiatry and Behavioral Sciences. "It gives doctors an alternative."
Anti-depression drugs come in two common varieties. Selective serotonin reuptake inhibitors (SSRIs), such as the popular Zoloft and Prozac, cause the brain chemical serotonin to linger in the gaps between neurons. These drugs are extremely effective but can interact with other drugs such as beta-blockers, which many elderly people take to quell heart problems.
The alternative to SSRIs - tricyclic antidepressants (TCAs) - can have side effects that make them less appealing. However, mirtazapine, a non-tricyclic that works similarly to TCA's, has few side effects or drug interactions. "Mirtazapine has TCA-like properties without the side effects," Schatzberg said. "A lot of people use it where they might have used a TCA, particularly in the elderly." Mirtazapine enhances the effects of serotonin and other brain chemicals and also acts as a mild sedative.
Schatzberg tested mirtazapine's effectiveness against paroxetine (sold under the name Paxil), a popular SSRI. In his trial, 255 depressed people 65 or older were randomly divided into groups taking either mirtazapine or paroxetine. Psychiatrists analyzed the patients' depression throughout an eight-week test period.
Although the drugs were equally effective by the end of the eight-week period, depression in patients on mirtazapine had eased significantly by day 14 compared with people taking paroxetine. Those patients also had less anxiety and an easier time sleeping. In addition, those who took mirtazapine had fewer side effects such as nausea, tremors or flatulence - side effects that caused 26 percent of those taking paroxetine to discontinue the trial compared with 15 percent of those on mirtazapine. During an extended eight-week phase after the initial trial, the two drugs remained equally effective.
Schatzberg said mirtazapine is also effective more quickly than SSRIs in younger people; however younger people are less likely to stay on the drug because it can cause some weight gain and grogginess. "Weight gain is a problem for younger patients," Schatzberg said. "There's less initiative to use the drug in these people."
These side effects that drive younger patients away can be a boon to the elderly who are less concerned about their weight but who suffer from anxiety and insomnia. "Depressed people who are older often have agitation," Schatzberg said. "Mirtazapine calmed these patients and helped them sleep, especially early on."
Schatzberg said that many doctors already use mirtazapine to treat depression in their elderly patients in order to avoid the drug interactions that are common with SSRIs. "But it certainly hasn't saturated the market in the elderly," he noted.
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