DRUG CHOICE IN DEPRESSION - SELECTIVE SEROTONIN REUPTAKE INHIBITORS OR TRICYCLIC ANTIDEPRESSANTS

Selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors (SSRIs) are no more effective or rapid in their onset of action than tricyclic antidepressants (TCAs), Meta-analyses of comparative trials suggest that there are no significant differences between these 2 classes of drugs in overall dropout rates or those due to inefficacy alone, However, a small difference in dropout rates due to adverse effects in favour of SSRIs has been reported. It is not known if this difference exists in general practice, where most antidepressants are prescribed, or if it will be sustained during longer term treatment, during which adaptation to some adverse effects might be expected to occur. There could be differences between individual drugs in each class. SSRIs cause less sedation and anticholinergic effects than TCAs, but more gastrointestinal disturbances, In the short term (at least), SSRIs cause less impairment on tests of cognition and psychomotor functioning, including tests that reflect performance in real life situations. This suggests that they could be less liable to cause, or contribute to, accidents in the home, in the workplace and on the road. SSRIs also have less anti-or-adrenergic effects than TCAs and may therefore be less prone to cause hypotension and falls, especially in the elderly. However, there are few epidemiological data available to support the view that SSRIs actually cause less falls or accidents in the real world. The selective reuptake inhibitors cause less serious cardiovascular effects than TCAs and are less lethal in overdose. However, patients treated with the former agents do not have a lower suicide rate than those treated with TCAs. This is consistent with the view that individuals who genuinely want to kill themselves will find a means of doing so. TCAs interact with more drugs than SSRIs, although most of the interactions with TCAs are due to the summation of sedative and antimuscarinic effects. Similar numbers of hazardous interactions occur with both classes of drugs. Although drug safety monitoring shows that SSRIs only rarely cause serious problems, some of the drugs are relatively new and it is, therefore, necessary to remain alert to the possibility of hitherto unrecognised adverse effects, especially after long term use. This holds true for the possibility of teratogenic effects because, in spite of the warnings issued, many women take drugs during pregnancy or become pregnant after taking them. SSRIs cost more than TCAs, although a proper assessment of costs and benefits has to take into consideration much more than just acquisition costs. Whether the advantages of SSRIs justify the additional cost compared with TCAs is a value judgement, but one that should be based on a critical overview of the scientific evidence rather than on other factors known to influence prescribing.