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Antidepressant medications
Different classes of antidepressants include monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and atypical antidepressants.
Monoamine oxidase inhibitors (MAOIs) are the earliest antidepressants. Examples of MAOIs include phenelzine (Nardil) and tranylcypromine (Parnate). MAOIs elevate the levels of neuro-chemicals in the brain synapses by inhibiting monoamine oxidase, the main enzyme that breaks down neuro-chemicals such as norepinephrine. MAOIs also impair the ability to break down tyramine, a substance found in aged cheese, wines, most nuts, chocolate, and other foods. Ingestion of tyramine-containing foods by a patient taking an MAOI drug can cause elevated blood levels of tyramine and dangerously high blood pressure. MAOIs also can interact with over-the-counter cold and cough medications to cause dangerously high blood pressures. Because of these potentially serious drug and food interactions MAOIs are usually only prescribed after other options have failed.
Tricyclic antidepressants (TCAs) were developed in the 1950s and 1960s to treat depression. They are called tricyclic antidepressants because their chemical structures consist of three chemical rings. TCAs work mainly by increasing the level of norepinephrine in the brain synapses, although they also may affect serotonin levels. Doctors often use TCAs to treat moderate to severe depression. Examples of tricyclic antidepressants are amitriptyline (Elavil), protryptyline (Vivactil), desipramine (Norpramin), nortriptyline (Aventyl, Pamelor), trimipramine (Surmontil) and Triavil. Tetracyclics are similar in action to tricyclics but their structure has four chemical rings. Examples include maprotiline (Ludiomil) and mirtazapine (Remeron). TCAs are safe and generally well tolerated when properly prescribed and administered. However, if taken in over-dose, TCAs can cause life threatening heart rhythm disturbances. Some TCAs can also have anti-cholinergic side effects. Anti-cholinergic side effects are due to blocking of the activity of the nerves responsible for heart rate control, gut motion control, and rate of saliva production. Thus some TCAs can produce dry mouth, constipation, and feeling of dizziness upon arising, a condition that results from low blood pressure upon standing (orthostatic hypotension). Anti-cholinergic side effects can also aggravate narrow angle glaucoma, urinary obstruction due to benign prostate hypertrophy, and cause delirium in the elderly. TCAs should also be avoided in patients with seizure disorders and history of strokes.
Selective serotonin reuptake inhibitors (SSRIs) are medications that increase the amount of serotonin neuro-chemical in the brain. SSRIs have been used successfully for a decade in the United States to treat depression. SSRIs have fewer side effects than the TCAs and MAOIs. SSRIs do not interact with tyranine in food, and do not have orthostatic hypotension and heart rhythm disturbances like traditional antidepressants, such as TCAs. Therefore, SSRIs are often the first-line treatment for depression. Examples of SSRIs include fluoxetine (Prozac), paroxetine (Paxil), sertraline (Zoloft), citalopram (Celexa), and fluvoxamine (Luvox).
SSRIs are generally well tolerated and side effects are usually mild. The most common side effects are nausea, diarrhea, and headache, but these side effects generally dissipate within the first month of use. Some patients experience sexual side effects such as decreased libido or delayed or inability to have an orgasm. Some patients experience tremors with SSRIs. Serotonergic syndrome is a serious neurologic condition associated with the use of SSRIs. It is characterized by high fevers, seizures, and heart rhythm disturbances. It is very rare, and has been reported only in very ill psychiatric patients taking multiple psychiatric medications.
Atypical antidepressants are so named because there is a lack of a common mode of action among them. They are not TCAs nor SSRIs but like them, atypical antidepressants increase the level of certain neuro-chemicals in the brain synapses. Examples include nefazodone (Serzone), trazodone (Desyrel), venlafaxine (Effexor), and bupropion (Wellbutrin). Bupropion (Wellbutrin) has also been approved by the United States Food and Drug Administration (FDA) for use in weaning addiction to cigarettes. It is also being studied to be used in treating attention deficit disorder (ADD/ADHD).
Lithium (Eskalith, Lithobid), valproate (Depakene, Depakote) and carbamazepine (Epitol, Tegretol) have been used to treat bipolar depression. Certain antipsychotics medications such as risperidone (Risperdal) and quetiapine (Seroquel) have also been used sometimes to treat bipolar depression.
Stimulants such as methylphenidate (Ritalin) or dextroamphetamine (Dexedrine) are faster acting than the other antidepressants. They may be used initially for several weeks in addition to an antidepressant to treat certain patients with severe depression.
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