(dailyRx News) Germany's Institute for Quality and Efficiency in Health Care (IQWiG) has investigated whether patients with depression benefit from taking selective serotonin and norepinephrine reuptake inhibitor (SNRI) drugs.
Until now in Germany, two SNRI drugs have been approved for use in that country: venlafaxine (Effexor) and duloxetine (Cymbalta). In its final report, published on August 18, IQWiG states that the benefit of both drugs has been proven compared to placebo: Patients respond better to the therapy and suffer less from the symptoms of depression. Moreover, there are indications that both drugs protect against relapse in addition to alleviating symptoms.
There are various assumptions about when and how depression occurs. The possible causes and influencing factors are manifold. What is not disputed is that the complete clinical picture of depression is the result of a complex interplay of biological and psychosocial factors. There are indications that a modification or reduction in the transfer of certain messenger substances in the central nervous system plays a part. This is where most drug therapies start their effect. The comparatively new SNRI drug class is intended to influence two of these messenger substances, called neurotransmitters, by inhibiting the reuptake of serotonin and norepinephrine.
IQWiG and its external experts found a total of 80 clinical trials that could be included in the assessment. Sixteen compared duloxetine with a placebo or another antidepressant, 62 tested venlafaxine in the same way, and two trials compared the two drugs directly with each other. The manufacturers of both the drugs investigated, Eli Lilly and Wyeth, respectively, provided a great deal of unpublished data to the institute.
In these trials, the effect of the drugs is mostly measured on scales that patients or health practitioners can use to document changes in symptoms. IQWiG's benefit assessment included outcomes such as the change in depression symptoms and accompanying symptoms such as anxiety, pain or sleep disorders, as well as mortality, suicidal tendency, quality of life, daily routine (social functioning level) and adverse drug effects.
The investigators concluded that acute-therapy patients respond better to both drugs than to a placebo. There is greater alleviation of symptoms, and in some cases they recede to such an extent that some patients no longer fulfill the criteria for a depression diagnosis.
As far as relapse prevention is concerned, there is at least an indication that patients benefit more from duloxetine and venlafaxine than from a placebo. In contrast to duloxetine, there is also proof that venlafaxine provides more effective protection than placebo against a renewed occurrence of depressive symptoms (recurrence prevention).
In the direct comparison of venlafaxine and duloxetine, neither drug displays superiority over the other with regard to alleviating depressive symptoms.
With reference to the health-related quality of life, an advantage was proven for duloxetine in the comparison with placebo, but not for venlafaxine. However, if the drugs are compared directly, there is no relevant difference. In comparison to a placebo, both drugs also improve the patient's ability to manage their daily routine (social functioning level).
In the comparison with another antidepressant drug class, selective serotonin reuptake inhibitors (SSRI), venlafaxine displays an advantage: It alleviates depressive symptoms better than the drugs it was compared with. However, the same does not apply to duloxetine.
The investigation into adverse drug effects revealed that venlafaxine is superior to duloxetine in the direct comparison, for fewer patients discontinued therapy due to side effects. In this context, however, both drugs are inferior to SSRIs.
With regard to accompanying symptoms of depression, such as anxiety, pain or sleep disorders, there is only one relevant difference revealed in the included trials: In the venlafaxine group, patients suffered less from anxiety conditions than in the placebo group. However, no relevant effect could be established for either of the two drugs with regard to the other accompanying symptoms investigated. This applies both to the comparison with a placebo and the comparison with other antidepressants.
Dr. Anna-Sabine Ernst