From the Guidelines

Elderly patients taking SSRIs are at risk of several side effects, including hyponatremia, gastrointestinal bleeding, and QT prolongation.

Hyponatremia: occurs in 0.5% to 12% of older adults, with a higher risk associated with SSRIs 1
Gastrointestinal bleeding: SSRIs and serotonin-norepinephrine reuptake inhibitors are associated with an increased risk, especially when used with antiplatelet or nonsteroidal anti-inflammatory drugs 1
QT prolongation: a dose-dependent effect, particularly with citalopram, escitalopram, and amitriptyline, with a higher risk in adults older than 60 years 1

Fluoxetine: generally not recommended for older adults due to its long half-life and side effects 1
Venlafaxine, vortioxetine, and mirtazapine: considered safer options in terms of drug interactions 1
Citalopram, escitalopram, sertraline, mirtazapine, and venlafaxine: preferred agents for older patients with depression, while paroxetine and fluoxetine should be avoided due to higher rates of adverse effects 1

A "start low, go slow" approach is recommended for antidepressant therapy in older persons 1
Lower starting doses, approximately 50% of the adult starting dose, are often recommended for older adults 1

From the Research

The use of Selective Serotonin Reuptake Inhibitors (SSRIs) in elderly patients can be associated with several side effects, including:

Hyponatremia, as reported in a case study where an 81-year-old male patient developed symptomatic hyponatremia while being treated with sertraline 2
Cardiovascular effects, such as changes in heart rate, blood pressure, and QT interval, as discussed in a qualitative narrative review of newer antidepressants 3
Gastrointestinal symptoms, such as nausea and vomiting, as well as dizziness and drowsiness, which can be intolerable for a significant minority of older patients 4, 5
Dry mouth, drowsiness, dizziness, and lethargy, which are more commonly associated with tricyclic antidepressants (TCAs) but can also occur with SSRIs 4

Studies have compared the side effect profiles of SSRIs with those of other antidepressants, including:

Tricyclic antidepressants (TCAs), which have been found to have a higher prevalence of side effects, such as dry mouth, drowsiness, dizziness, and lethargy 4
Non-serotonergic antidepressants, such as bupropion, which may be a suitable alternative for patients who experience severe side effects with SSRIs 2
TCA-related drugs, such as mianserin and trazodone, which have been found to be comparable to SSRIs in terms of tolerability 4

When prescribing SSRIs to elderly patients, it is essential to consider the potential for:

Drug-drug interactions, due to the increased likelihood of polypharmacy in this age group 6
Changes in pharmacodynamic and pharmacokinetic properties of drugs, due to age-related physiological changes 6
Increased sensitivity to side effects, due to decreased renal function and other age-related factors 6, 5