Certain brain chemicals called neurotransmitters are associated with depression, including the neurotransmitters serotonin (ser-oh-TOE-nin), norepinephrine (nor-ep-ih-NEF-rin) and dopamine (DOE-puh-mene). Research suggests that abnormalities in neurotransmitter activity can affect mood and behavior.

Tricyclic antidepressants (TCAs) inhibit the reabsorption (reuptake) of serotonin and norepinephrine. To a lesser extent, TCAs also inhibit reabsorption of dopamine. These antidepressants also block certain cell receptors, which accounts for many of their side effects. TCAs are called tricyclic because of their chemical structure. They were among the earliest of antidepressants, hitting the market in the 1960s, and they remained the first line of treatment for depression through the 1980s, before newer antidepressants arrived.

Here are the TCAs that have been approved by the Food and Drug Administration specifically to treat depression, with their generic or chemical names followed by available brand names in parentheses:

• Amitriptyline
• Amoxapine
• Desipramine (Norpramin)
• Doxepin (Sinequan)
• Imipramine (Tofranil)
• Nortriptyline (Pamelor)
• Protriptyline (Vivactil)
• Trimipramine (Surmontil)

Some of these medications come in forms that must be injected or as oral solutions that must be mixed with liquids, such as water or juice.

Some of these medications may also be used to treat conditions other than depression.

Because TCAs are less selective about which cells they affect, they typically have more side effects than other antidepressants.

Side effects of TCAs include:

• Drowsiness
• Dry mouth
• Blurred vision
• Constipation
• Urinary retention
• Dizziness
• Impaired sexual functioning
• Increased heart rate
• Disorientation or confusion
• Headache
• Low blood pressure
• Sensitivity to sunlight
• Increased appetite
• Weight gain
• Nausea
• Weakness

In general, avoid tricyclic antidepressants if you have narrow-angle glaucoma, an enlarged prostate (benign prostatic hyperplasia) or certain types of heart disease. TCAs are associated with a higher risk of heart attack. TCAs may affect blood sugar levels. If you have diabetes, you may need to check your blood sugar more often. TCAs should be used with caution if you have a history of seizures or thyroid problems.

TCAs aren't considered addictive. However, stopping treatment abruptly or missing several doses can cause withdrawal-like symptoms, including:

• Nausea
• Headache
• Dizziness
• Lethargy
• Flu-like symptoms

This is sometimes called discontinuation syndrome. Talk to your doctor before stopping so that you can gradually taper off the medication.

In some cases, antidepressants may be associated with worsening symptoms of depression or suicidal thoughts or behavior, particularly early in treatment or when you change your dosage. Be sure to talk to your doctor about any changes in your symptoms. You may need more careful monitoring at the beginning of treatment or upon a change in treatment, or you may need to stop the medication if your symptoms worsen.