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CMAJ. 1998 Nov 17;159(10):1245-52.

Adverse effects associated with selective serotonin reuptake inhibitors and tricyclic antidepressants: a meta-analysis.

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Canadian Coordinating Office for Health Technology Assessment, Ottawa, Ont.



The use of antidepressant medications and the resulting costs have increased dramatically in recent years, partly because of the introduction of selective serotonin reuptake inhibitors (SSRIs). An assessment of the clinical and economic aspects of SSRIs compared with the older tricyclic antidepressants (TCAs) was initiated to generate information for purchasers of these drugs as well as clinicians. One component of this study was an examination of the adverse effects associated with the use of these drugs.


Searches of bibliographic databases (for January 1980 through May 1996) and manual scanning of both peer-reviewed publications and other documents were used to identify double-blind, randomized controlled trials involving at least one SSRI and one TCA. For the study of adverse effects, only trials that had at least 20 patients in each trial arm and that reported rates of adverse effects in both arms were retained. In total 84 trials reporting on 18 adverse effects were available. Meta-analyses were undertaken to calculate pooled differences in rates of adverse effects. The question of whether the method of eliciting information from patients about adverse effects made a difference in the findings was also examined. Finally, differences in drop-out rates due to adverse effects were calculated.


The crude rates of occurrence of adverse effects ranged from 4% (palpitations) to 26% (nausea) for SSRIs and from 4% (diarrhea) to 27% (dry mouth) for TCAs. The differences in the rates of adverse effects between the 2 types of drugs ranged from 14% more with SSRIs (for nausea) to 11% more with TCAs (for constipation). The results did not depend on the method of eliciting information from patients. There were no statistically significant differences between drug classes in terms of drop-outs due to adverse effects.


SSRIs and TCAs are both associated with adverse effects, although the key effects differ between the drug classes. Further explanation of the adverse effects and their relation to discontinuation of medication will require better studies involving prospective collection of quality-of-life data.

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