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Tricyclic antidepressants (TCAs), Selective serotonin re-uptake inhibitors (SSRIs)

Medications used to treat depression.

The two most common types of antidepressants are tricyclic antidepressants (TCAs) and selective serotonin re-uptake inhibitors (SSRIs). Examples of TCAs include nortriptyline (also known by the brand name Pamelor), imipramine (Tofranil), and desipramine (Norpramin). Examples of SSRIs include fluoxetine (Prozac), sertraline (Zoloft), and paroxetine (Paxil). Clinical studies have shown that some people benefit from these medications.

Tricyclic antidepressants (TCAs)

Before using TCAs, it is necessary to have a medical history and examination of the patient, including an electrocardiogram (EKG). Not everyone develops side effects when taking TCAs, but the most common side effects include: dry mouth, impaired ability to focus vision at close range, constipation, urinary hesitation, dizziness, weight gain, and sedation. TCAs may produce minor cardiovascular changes such as orthostatic hypotension (low blood pressure when the person stands up, often causing light-headedness), hypertension, rapid heart beat, and minor changes in the electrical activity of the heart, which may show in the electrocardiogram (EKG). Most of these side effects can be minimized by slowly adjusting the dose of the drug.

During treatment with TCAs, patients should be monitored by a physician trained in the management of these medications. It is recommended that he or she perform regular blood pressure, heart rate, and EKG monitoring. TCAs may interact with other medications the patient is taking, so it is important to consult a doctor before doing so. Finally, the TCAs should not be stopped abruptly, as this may induce mild withdrawal side effects (malaise, chills, stomachache, flu-like symptoms). Though they are safe if carefully monitored and taken as prescribed, TCAs can be lethal if taken in overdose.

Selective serotonin re-uptake inhibitors (SSRIs)

The reports that SSRIs are effective in treating adults with major depressive disorder (MDD), together with the findings that SSRIs have a relatively benign side effect profile, low lethality after an overdose, and once-a-day administration, have encouraged the use of SSRIs.

Several studies have reported 70-90% response rate to fluoxetine or sertraline for the treatment of adolescents with major depressive disorder, but the results of these studies are not conclusive because they have methodological limitations. A recent, large, well-performed investigation showed that fluoxetine was more effective for the treatment of depressed children and adolescents than a placebo. Despite the significant response to fluoxetine, many patients had only partial improvement.

Overall, the SSRIs have similar effectiveness and side effects as TCAs. The most common side effects include nausea, stomachache, diarrhea, headaches, mild tremors, sweating, sleep disturbance, sedation, restlessness, lack of appetite, decreased weight, vivid dreams, and sexual dysfunction (inability to have an orgasm or delayed ejaculation). Most of these side effects are temporary and may be diminished by reducing the dose or discontinuing the medication. There are no specific laboratory tests required before administering SSRIs. These drugs do have potentially harmful interactions with several commonly prescribed drugs; therefore, all physicians should be informed if someone is taking an SSRI.

Patients who do not respond to treatment

The most common reasons for failure of treatment are inadequate medication dosage or length of medication trial, lack of compliance with treatment, exposure to chronic or severe life events that require different modalities of therapy, existence of other psychiatric disorders (e.g., substance abuse, anxiety disorder), and misdiagnosis. In adults with resistant depression, several types of combinations of medications and ECT (electroconvulsive therapy) have been found to be useful.

Additional topics

Psychology EncyclopediaPsychological Dictionary: Abacus to Courage