Antidepressant Drugs Side Effects

Major depressive disorder and mild, chronic depression affect approximately 18 million adults ages 18 and older in the United States, according to 2010 information from the National Institute of Mental Health. People with depression experience excessive and persistent feelings of sadness and worthlessness, and a loss of pleasure, according to the American Psychiatric Association. Antidepressant drugs are part of the standard protocol to treat depression in some patients, yet these medications can have side effects.

Size

Antidepressant drugs are the third leading category of prescription drugs dispensed in the United States, growing from approximately 144 million prescriptions in 2005 to 169 million in 2009, according to IMS Health.

Classes

Antidepressants enhance the level and function of chemical messengers in the brain called neurotransmitters, such as serotonin and norepinephrine, according to MayoClinic.com. There are three classes of antidepressants that enhance levels of neurotransmitters in the brain: Selective neurotransmitter reuptake inhibitors block the reabsorption of the specific chemical messenger by the pre-synaptic nerve cell. Tricyclic antidepressants block the reuptake of neurotransmitters, but are not selective to the particular chemical messenger. Monoamine oxidase inhibitors block the enzyme that breaks down the neurotransmitter.

Types

Prozac, Celexa, Lexapro and Zoloft are some of the popular brand-name selective serotonin reuptake inhibitors. Effexor and Cymbalta are brand-name serotonin and norepinephrine reuptake inhibitors. Amitriptyline, imipramine and desipramine are generic tricyclic drugs. Phenelzine and isocarboxazid are generic monoamine oxidase inhibitors.

Side Effects

Selective serotonin reuptake inhibitors are often the first choice in antidepressant therapy because these drugs are relatively safe and effective, according to MayoClinic.com. Yet SSRIs can cause drowsiness, fatigue and sexual side effects that inhibit the ability to achieve orgasm in women and delay the ability to ejaculate in men. SNRIs, such as Effexor, can increase blood pressure. Tricyclic antidepressants can cause dry mouth, sedation, constipation, difficulty urinating, weight gain, erectile dysfunction and death by overdose, and are not prescribed to the elderly or people with heart disease or low blood pressure. MAO inhibitors have dangerous side effects and are usually prescribed when other antidepressants fail to work. Side effects from MAO inhibitors include dizziness, upset stomach, dry mouth and drowsiness. When combined with foods and drinks containing tyramine, such as aged cheeses, smoked fish and wine, MAO inhibitors can cause very high blood pressure that could be fatal.

Warning

The U.S. Food and Drug Administration has mandated manufacturers for all classes of antidepressant drugs to include a black box warning on product labels to warn about increased risks of suicidal thinking and behavior when taking these drugs. Research published in the "Archives of General Psychiatry" discovered that risk of suicide is equal across all classes and types of antidepressants, supporting the decision by the FDA to mandate black box warnings on all antidepressant drugs. Scientists involved with this research suggest that treatment decisions should be based on efficacy of the particular antidepressant drug and that physicians should monitor patients with vigilance.