Like all medications, antidepressants may produce unwanted side effects. While various drugs have different side effect profiles, most individuals experience fewer side effects with the newer antidepressants (example: SSRIs, SNRIs).

Some symptoms will go away as the body adjusts to the medication. Other side effects are more troubling and may require a change in medication or the addition of other medications to treat the side effects. Some of these side effects include weight gain, sleep disturbances (either interrupted or excessive sleep) and sexual dysfunction.

The following is a summary of common side effects for the major classes of antidepressants. Remember, this list is not exhaustive and it is impossible to predict what side effects, if any, a person will experience. Patients should consult their physician about any side effects they think they may be experiencing.

SSRIs—paroxetine (Paxil); fluoxetine (Prozac); sertraline (Zoloft); fluvoxamine (Luvox); citalopram (Celexa)—are among the most widely prescribed medications in the world. It is useful to divide side effects into acute versus chronic.

The acute side effects occur early in treatment and for the most part tend to disappear over time. Acute side effects of SSRIs include stomach upset, nausea, fatigue, headache, fatigue, tremor, nervousness and dry mouth. Some of the more persistent, or chronic, side effects are daytime fatigue, insomnia, sexual problems (especially problems experiencing an orgasm) and weight gain.

Some patients, particularly those over 35 or with medical problems, may experience a change in EKG (electrocardiogram) readings that measure certain heart function. For this reason, it is important to consult a physician before taking these medications. Those over 35, or with medical problems, should have an EKG prior to starting a tricyclic antidepressant.

The greater side effects and lesser safety of tricyclic antidepressants are the main reasons they are no longer the first line of treatment. Side effects of tricyclics include dry mouth, postural blood pressure changes (drop in blood pressure when getting up quickly, resulting in dizziness), constipation, difficulty urinating, blurred vision, weight gain and drowsiness.

An overdose of a tricyclic medication is serious and potentially lethal. It requires immediate medical attention. Symptoms of an overdose usually develop within an hour of ingestion and may start with rapid heartbeat, dilated pupils, flushed face and agitation, and progress to confusion, loss of consciousness, seizures, irregular heart rate, cardiorespiratory collapse and death.

Commonly encountered side effects are not a main drawback of MAOIs. The major problem is the risk of dangerously high blood pressure if certain foods or medications are consumed while on a MAOI. This is referred to as the Cheese Reaction because aged cheese contains a high level of tyramine, the chemical that builds up if ingested while on a MAOI (see MAOI Requirements). Most patients are instructed to carry an “antidote” (such as nifedipine) in case they begin to experience signs of elevated blood pressure while on a MAOI.

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