The side-effect profile of an antidepressant is a particular consideration in older patients, who are more susceptible to side effects from all medications.

Tricyclics
The tricyclic antidepressants have a number of notable side effects which may make existing problems worse in the older patient. Most troublesome are the anticholinergic effects which cause dry mouth, urinary retention, constipation and psychomotor impairment. Memory and cognitive processes may also be impaired with the TCAs. Because of their effect on conduction, many TCAs are contraindicated in patients with existing heartblock. The TCAs are also associated

with orthostatic hypotension, again of concern in the elderly because of the increased risk of falls.

If a TCA is indicated, the best choices for the elderly are nortriptyline (lower potential to cause hypotension) and desipramine (lower anticholinergic activity). Blood levels can also be done with nortriptyline and desipramine, allowing physicians to objectively monitor therapeutic response and tailor the dose accordingly.

SSRIs and Newer Agents
Selective serotonin reuptake inhibitors along with the newer cyclic agents are safer than the TCAs and they avoid TCA-induced anticholinergic effects. If any of the newer agents are chosen for the older depressed patient, consideration should be given to the half-life of the medication. SSRIs with a short half-life include fluvoxamine, paroxetine and sertraline, while nefazodone, venlafaxine and bupropion are also short-acting. As such, they are a more appropriate choice for older patients than long acting agents such as fluoxetine (which has a half-life that can persist for weeks).

Many older patients require other medications for a variety of conditions as well; drug-drug interactions need to be reviewed prior to prescribing. [see Drug-Drug Interactions]. The adage to "start low and go slow" is particularly relevant in older patients, especially if the patient is frail or has other medical problems.

Differences between the SSRIs
As a class of antidepressant agents, the SSRIs share many features, including side effects. However, they do vary in side effect intensity and the likelihood of these effects occurring. If one medication within this class of antidepressants proves troublesome, a different medication still within the same drug class may be better tolerated. Following is a comparison of fluoxetine (Prozac), sertraline (Zoloft), fluvoxamine (Luvox) and paroxetine (Paxil). (From the Clinical Handbook of Psychotropic Drugs. 6th revised edition, 1996. Editors Kalyna Z. Bezchlibnyk-Butler, J. Joel Jeffries. Clarke Institute of Psychiatry, Toronto, Canada.)

Anticholinergic effects (dry mouth, blurred vision, constipation, sweating, problems with urination). As a drug class, the SSRIs do not cause significant side effects in this category. Fluoxetine is least likely to cause dry mouth; fluoxetine and sertraline are least likely to cause constipation as well as sweating. Blurred vision and problems with urination are uncommon and equally likely with each of the four agents.
Central nervous system (CNS) effects (drowsiness, sedation, insomnia, excitement, confusion, headache). Drowsiness and sedation are equally likely with all four agents, as is insomnia (especially with fluoxetine if given in the evening). Excitement and confusion are least likely with paroxetine, while the incidence of headache is similar with all four agents.

Tremor: All four agents are equally likely to cause tremor.

Dizziness: Fluvoxamine is least likely to cause dizziness.

Stomach upset (nausea): Fluvoxamine and sertraline are most likely to cause stomach upset but upset stomach is common with all SSRIs.

Weakness/fatigue: Sertraline is least likely to cause weakness or fatigue.

Weight gain/loss: All four agents are associated with equal weight loss.

Sexual dysfunction: Sertraline and fluvoxamine are least likely to cause sexual disturbances.

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