A Guide to Antidepressants

There are many types of antidepressants, old and new. Find out how they differ and learn which one might be right for you.

Antidepressants are the treatment of choice for moderate to severe depression. Although antidepressants may not cure depression, they can reduce your symptoms. Learning the facts about antidepressants and weighing the benefits against the risks can help you make an informed decision about whether an antidepressant is right for you.

There are a number of equally effective antidepressants that have emerged in the past two decades. Antidepressants are categorized based on the way they work. Antidepressants are generally divided into five main types: monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and atypical antidepressants.

Monoamine Oxidase Inhibitors

Introduced in the 1950s, monoamine oxidase inhibitors were the first antidepressants. Monoamine neurotransmitters are chemicals in the brain, such as norepinephrine, dopamine, and serotonin, that regulate your mood. MAOIs work by blocking an enzyme that breaks down monamines, so that there are more of them available to your body.

MAOIs can have numerous side effects; the most common of these include daytime sedation, dizziness, dry mouth, nervousness, muscle aches, paresthesia (tingling sensation), insomnia, weight gain, sexual dysfunction, and urinary difficulty.

MAOIs generally require diet restrictions because they can cause dangerously high blood pressure when taken with certain foods containing tyramine, found in some cheeses, beer, and fermented soy products. The most significant risk associated with the use of MAOIs is the potential for interactions with over-the-counter and prescription medicines, illicit drugs, and certain supplements.

The use of MAOIs has declined over the past several decades because of concern about the food and drug interactions and side effects, and with the introduction of newer, safer antidepressants. MAOIs are typically reserved for the treatment of major depressive disorder in patients with atypical features and when other antidepressants have failed.

Currently available MAOIs include Nardil (phenelzine), Parnate (tranylcypromine), Marplan (isocarboxazid), and Emsam (selegiline transdermal system).

Tricyclic Antidepressants

Tricyclic antidepressants, a class of antidepressants that also dates back to the 1950s, are named after their three-ring chemical structures. TCAs maintain higher levels of serotonin and norepinephrine in the brain and are used in the treatment of clinical depression, neuropathic pain (nerve pain), nocturnal enuresis (bed wetting), and attention-deficit hyperactivity disorder.

Tricyclic antidepressants tend to cause side effects including dry mouth and eyes, urinary hesitancy, and sometimes retention and constipation. Other side effects include increased heart rate, drowsiness, blurred vision, dizziness, confusion, and sexual dysfunction. Fatal toxicity with TCAs can occur at approximately 10 times normal dosages.

Currently available TCAs include Elavil (amitriptyline), Anafranil (clomipramine), Norpramin (desipramine), Tofranil (imipramine), Sinequan (doxepin), and Pamelor (nortriptyline).

Selective Serotonin Reuptake Inhibitors

SSRIs were developed in response to the need for better-tolerated, safer antidepressants than the TCAs and MAOIs, but with equal efficacy in the treatment of depression. SSRIs have become the most frequently prescribed antidepressants for depression and anxiety disorders. SSRIs help maintain higher levels of serotonin in the brain.

SSRIs typically have fewer side effects than earlier antidepressants, although nausea, diarrhea, drowsiness, dry mouth, nervousness, anxiety, insomnia, decreased appetite, and sexual dysfunction may occur.

Currently available SSRIs include Prozac (fluoxetine), Celexa (citalopram), Paxil (paroxetine), Lexapro (escitalopram), Luvox (fluvoxamine) and Zoloft (sertraline).

Serotonin-Norepinephrine Reuptake Inhibitors

SNRIs maintain higher levels of serotonin, norepinephrine and, to a lesser degree, dopamine in the brain. SNRIs are commonly used in the treatment of depression, neuropathic pain (nerve pain), panic disorder, and anxiety.

SNRIs typically have similar side effects to SSRIs, including nausea, dizziness, insomnia, somnolence, dry mouth, and sexual dysfunction. There may also be a withdrawal syndrome, marked by nausea, somnolence, insomnia, and anxiety, upon discontinuation of these medications that generally necessitates dosage tapering.

Currently available SNRIs include Effexor (venlafaxine), Cymbalta (duloxetine), and Pristiq (desvenlafaxine).

Atypical Antidepressants

These medications are referred to as "atypical" because they don't fit neatly into any other antidepressant category. Atypical antidepressants include:

  • Desyrel (trazodone), which promotes higher serotonin levels in the brain. Desyrel commonly causes sedation, dizziness, and headache.
  • Wellbutrin (bupropion), which increases levels of dopamine and to a lesser extent, norepinephrine. The most common side effects with Wellbutrin include insomnia, headache, tremors, nausea, and rarely, seizures.
  • Remeron (mirtazapine), which increases levels of norepinephrine and serotonin. The most common side effects with Remeron include fatigue, dizziness, transient sedation, and weight gain.

It takes time to find the antidepressant that is right for you. The more you know about your antidepressant, the better equipped you’ll be to deal with side effects, avoid dangerous drug interactions, and minimize other safety concerns.

Learn more about antidepressants at PDR Health.

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