Selective serotonin reuptake inhibitors (SSRIs)

Sexual dysfunction (primarily, delayed orgasm but also loss of desire and erectile dysfunction in some people), nausea, diarrhea, headache, weight loss (short-term), weight gain (long-term), discontinuation syndrome*, forgetfulness, blunting of emotions, and easy bruising

SSRIs are the most commonly used class of antidepressants. They are also effective for generalized anxiety disorder, obsessive-compulsive disorder, panic disorder, phobic disorder, posttraumatic stress disorder, premenstrual dysphoric disorder, and bulimia.

Toxicity due to overdosage is less serious than that with other antidepressants.

Norepinephrine-dopamine reuptake inhibitors

Headache, agitation, discontinuation syndrome*, high blood pressure in a few people, and rarely seizures

attention-deficit/hyperactivity disorder or and those trying to stop smoking

Serotonin modulators (5-HT₂ blockers)

Drowsiness and weight gain

Prolonged drowsiness, painful and persistent erection (priapism), and an excessive decrease in blood pressure when a person stands

insomnia.

Serotonin-norepinephrine reuptake inhibitors

Nausea, dry mouth, discontinuation syndrome*, and, if high doses are taken, an increase in blood pressure

Most of the side effects can be prevented or minimized when low doses are used and when changes in dosages are made slowly.

Heterocyclic (including tricyclic) antidepressants

Drowsiness, weight gain, increased heart rate and decreased blood pressure when a person stands (orthostatic hypotension), dry mouth, confusion, blurred vision, constipation, difficulty starting to urinate, delayed orgasm, and discontinuation syndrome*

These medications are usually not prescribed for older adults because side effects are usually more pronounced in them.

Overdosage can cause serious, potentially life-threatening toxicity.

Monoamine oxidase inhibitors (MAOIs)

Insomnia, nausea, weight gain, sexual dysfunction (loss of desire, delayed orgasm, and erectile dysfunction), pins-and-needles sensation, dizziness, decreased blood pressure (particularly when a person stands), and discontinuation syndrome*

People who take these medications must follow dietary restrictions and avoid using certain medications to avoid a serious reaction involving a sudden, severe increase in blood pressure with a severe, throbbing headache (hypertensive crisis).

Psychostimulants

Nervousness, tremor, insomnia, and dry mouth

These medications are usually used with antidepressants. Used alone, they are usually ineffective as antidepressants.

Melatonergic antidepressant

Agomelatine

Headache, nausea, and diarrhea

Agomelatine has fewer side effects than most antidepressants. It does not cause daytime drowsiness, insomnia, weight gain, or sexual dysfunction.

Agomelatine may increase liver enzyme levels. These levels should be measured before therapy is started and periodically thereafter.

Dizziness, increased blood pressure, feeling of detachment

Dizziness, increased blood pressure, feeling of detachment