Insomnia from SSRIs

The antidepressant mirtazapine is pharmacologically similar to mianserin. It has a slightly weaker blocking action at i-adrenoceptors, and this is claimed to give it a dual mode of action, increasing the release of both noradrenaline and serotonin (1). It is claimed to have a more rapid onset of action than some SSRIs, but this may be due to its prominent sedative effect, which improves insomnia from the start of treatment. 

Nervousness and agitation in some patients early in treatment are characteristic side effects of the SSRIs. These too have been reported to be dose related. In the fluoxetine database, these side effects were more common with the 60-mg dose than with the 20-mg dose and were associated with some insomnia (G. L. Cooper 1988]. Although in general the various SSRIs differ little one from the other, there appear to be some differences in their propensity for producing nausea and nervousness. 

At the present time, the TCAs are used primarily in depression that is unresponsive to more commonly used antidepressants such as the SSRIs or SNRIs. Their loss of popularity stems in large part from relatively poorer tolerability compared with newer agents, to difficulty of use, and to lethality in overdose. Other uses for TCAs include the treatment of pain conditions, enuresis, and insomnia. 

Because of their selective action on serotonin, the manufacturer of SSRIs claim there are fewer side effects from this class of drug than those of the tricyclics and MAOIs. These other drugs affect many neurotransmitters in the brain and therefore result in many side effects. However, the SSRIs can cause stomach upset, insomnia, and anxiety. 

Fluoxetine and other selective serotonin reuptake inhibitors (SSRIs) have been associated with increasing suicidal ideation in some populations of patients. Recent studies have led the British Department of Health to warn physicians against using paroxetine off label. Fluoxetine was specifically exempted from this recommendation. Long-term studies of patients with depression who were treated with fluoxetine have shown it to be fairly well tolerated. Primary adverse effects include nausea (23%), headache (21%), and insomnia (20%). 

The monoamine oxidase inhibitors are associated with a number of undesirable side effects including weight gain, postural hypotension, sexual dysfunction, and insomnia. The most serious side effect is the risk of tyramine-re-lated hypertensive crisis, often referred to as the "cheese effect," which can be fatal. To avoid this situation patients taking MAOIs must limit their tyramine intake, and the restrictive diet required to accomplish this leads to low patient compliance. A similar interaction occurs when switching patients from MAOI to SSRI therapy, and a minimum 2-week washout period before commencement of SSRI therapy is essential to allow MAO levels to return to normal. The therapeutic effects of the TCAs derive from their inhibition of serotonin and norepinephrine uptake, al-... 

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