Antidepressants
Antidepressants
Definition
Antidepressants are medications that are used primarily to treat depression. Antidepressant drugs are also sometimes used to treat other psychological disorders, such as anxiety disorders and eating disorders. Because they are thought to increase the effectiveness of some pain medications, they are sometimes used in the treatment of migraine-type headaches. They are also used as a component of smoking cessation programs, and in the treatment of fibromyalgia and some types of sleep disorders.
Description
Antidepressant drugs can be used to treat depression and other disorders. A person with depression has symptoms that last for at least two weeks. These symptoms can include feelings of sadness, emptiness, guilt, or worthlessness, loss of interest in previously pleasurable activities, changes in eating and sleeping patterns, fatigue, lethargy or agitation, difficulty concentrating, and suicidal thoughts. Antidepressant drugs are not the only treatment for depression; psychotherapy and other treatments are also independently effective in alleviating depression. Antidepressant drugs, if prescribed, are often used in combination with these other treatments.
The type of antidepressant medication prescribed depends on the particular array of symptoms a patient displays or reports. There are several different types of antidepressant drugs. All of them work by altering the level or activity of neurotransmitters in the brain. Neurotransmitters are chemicals that are released by neurons, or nerve cells. They attach to other neurons and activate them in various ways. Although antidepressant drugs affect communication between neurons within hours after these drugs are ingested, symptoms of depression usually improve only after a few weeks of taking the medication. Some people notice improvement in symptoms after only two weeks, but many people notice a benefit only after six to eight weeks of using the medication. The reason for this delayed effect of antidepressants is not entirely clear. One theory is related to the finding that the changes in neurotransmitter activity caused by antidepressants increase the release of other chemicals, called neurotrophins, in the brain. In the normal brain, neurotrophins help neurons to grow and connect to other neurons. People with depression sometimes have shrinkage of neurons in parts of the brain. When more neurotrophins are present, neurons in these areas of the brain can grow.
The main classes of antidepressant drugs are tricyclics, monoamine oxidase inhibitors (MAOIs), selective serotonin reuptake inhibitors (SSRIs), and atypical antidepressants. A patient who does not improve with one type of antidepressant drug may sometimes be helped by another type of antidepressant, because different drugs work in different ways.
Tricyclic antidepressants
The first class of drugs used to treat depression, from the 1960s through the 1980s, was that of tricyclic antidepressants. Tricyclic antidepressants work by preventing neurons from reabsorbing the neurotransmitters serotonin, dopamine, and norepinephrine, after they are released. This means that the neurotransmitters are able to remain in the gaps between neurons for a longer period of time, thus continuing to activate the neurons that receive them. Tricyclic anti-depressants can have side effects because they can prevent nerve cells from functioning normally, and because they can prevent additional neurotransmitters from working effectively. For example, they block the activity of histamine, a neurotransmitter that is involved in keeping people alert and awake. They also block the activity of acetylcholine, a neurotransmitter that is involved in many automatic bodily activities. Tricyclic antidepressants include imipramine (trade name Tofranil), amitriptyline (trade names Elavil, Endep), clomipramine (trade name Anafranil), doxepin (trade names Sinequan, Adapin), desipramine (trade name Norpramin), nortriptyline (trade name Pamelor), protriptyline (trade name Vivactil), and trimipramine (trade name Surmontil).
MAOIs
The monoamine oxidase inhibitors are drugs that prevent neurotransmitters such as dopamine, serotonin and norepinephrine from being broken down into inactive chemicals. This means that, when MAOIs are used, more of these neurotransmitters are available to send messages in the brain. MAOIs can have potentially serious side effects because they also prevent the amino acid tyramine from being broken down. Tyramine is a chemical that the body needs, and it is found in foods like aged cheese, smoked and pickled meats and fish, and raisins. If tyramine that is ingested cannot be broken down, it can accumulate in the body, causing increased blood pressure and possibly strokes. The MAOIs include isocarboxazid (trade name Mar-plan), phenelzine (trade name Nardil), and tranylcypromine (trade name Parnate).
SSRIs
The selective serotonin reuptake inhibitors are drugs that work by preventing neurons from reabsorbing serotonin after it is released, so that the effect of serotonin on adjoining neurons is prolonged. The SSRIs include citalopram (trade name Celexa), escitalopram (trade name Lexapro), fluoxetine (trade name Prozac), fluvoxamine (trade name Luvox), paroxetine (trade name Paxil ), and sertraline (trade name Zoloft).
Atypical antidepressants
The atypical antidepressants are a miscellaneous collection of drugs. One of these drugs, bupropion (trade name Wellbutrin), prevents dopamine, and to some extent, norepinephrine, from being reabsorbed by neurons, so that these neurotransmitters are able to have a more prolonged effect. Another drug, venlafaxine (trade name Effexor), prevents serotonin, and to a smaller extent, norepinephrine and dopamine, from being reabsorbed. Other atypical antidepressants include mirtazapine (trade name Remeron), trazodone (trade name Desyrel) and duloxetine (trade name Cymbalta).
Recommended dosage
The dosage of antidepressants depends on the particular drug being prescribed, and other factors such as the age of the patient, the patient’s body chemistry, and the patient’s body weight. Patients are usually started on a low dose to minimize side effects, and the dose is gradually increased over time to a level that is therapeutic. Newer antidepressants, however, may be started at the therapeutic dosage level.
Precautions
In 2005, the U.S. Food and Drug Administration warned that SSRI drugs may increase suicidal thoughts in children and adolescents. It urged health-care practitioners and families of patients to carefully monitor people, of any age, who take these drugs. The National Institutes of Health is currently carrying out research to study the nature of the association between suicidal thoughts and antidepressant drugs. Canadian researchers at McGill University also found that adults over age 50 who take SSRIs are at double the risk of bone fractures.
Antidepressants can precipitate mania in people who are susceptible to bipolar disorder. Therefore, a health-care practitioner typically takes a detailed history of a patient before prescribing antidepressants. Various medical problems may affect the effectiveness or risks of antidepressants. These include, but are not limited to, angina, headaches, epilepsy, recent heart attacks or stroke, kidney disease, and diabetes. Some antidepressants may affect a fetus, therefore pregnant women should inform their doctors about their condition before antidepressants are prescribed. Patients taking tricyclic antidepressants should carefully adhere to the dietary restrictions provided by their doctor, in order to avoid potentially serious side effects. Patients who stop taking antidepressants may experience withdrawal symptoms if the drugs are abruptly discontinued.
KEY TERMS
Anxiety disorder —A type of psychological disorder characterized by unrealistic, irrational fear or intense anxiety.
Eating disorder —A type of psychological disorder characterized by disturbances in eating patterns, extreme concern about weight gain and unhealthy efforts to control weight.
Sleeping disorders —Disorders in which people experience disturbances of sleep.
Fibromyalgia —A condition in which a person experiences chronic pain in the muscles and soft tissues around joints.
Mania —A state in which a person experiences intense excitement and euphoria.
Stroke —A temporary loss of normal blood flow to an area of the brain, caused by blockage or rupture of a blood vessel.
Side effects
People who take antidepressants may experience side effects. Different people experience different side effects. Such side effects may include dry mouth, constipation, nausea, bladder problems, sexual problems, blurred vision, dizziness, daytime drowsiness, insomnia, increased heart rate, headache, nervousness, and agitation. The newer antidepressants are thought to have fewer and less troublesome side effects than the tricyclic antidepressants and the MAOIs.
Interactions
Antidepressants may result in dangerous side effects if taken in combination with other medications. There can also be dangerous side effects if different types of antidepressants are combined with each other. Patients should inform their doctor about all other medications and herbal supplements they are taking before antidepressant drugs are prescribed. Alcohol or other recreational drugs may decrease the effectiveness of antidepressants. Antidepressants may increase the intoxicating effect of alcohol.
Resources
BOOKS
American Psychiatric Association. Diagnostical and Statistical Manual of Mental Disorders, 4th edition, Text revision. Washington, D.C.:American Psychiatric Association, 2000.
Diamond, Ronald, J. Instant Psychopharmacology. 2nd edition. New York: W.W. Norton and Company, 2002.
Dunbar, Katherine Read, ed. Antidepressants. Farmington Hills, MI: Greenhaven Press, 2006.
Kalat, James W. Biological Psychology. 9th edition. Belmont, CA: Thomson Wadsworth, 2007.
OTHER
“New NIMH Research Strives to Understand How Anti-depressants May Be Associated with Suicidal Thoughts and Actions.” National Institutes of Health. 2006. <http://www.nih.gov/news/pr/nov2006/nimh-13.htm> (January 12, 2006).
“Medications.” National Institutes of Mental Health. 2002. <http://www.nimh.nih.gov/publicat/medicate.cfm> (January 12, 2006).
“Drug Information: Antidepressants, Monoamine Oxidase (MAO) Inhibitor (Systemic).” Medline Plus. 2005. <http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202054.html> (January 2006).
“Drug Information: Antidepressants, Tricyclic (Systemic).” Medline Plus. 2005. <http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202055.html> (January 2006).
“Daily Use of Antidepressants Associated with Increased Risk of Fracture in Older Adults” Newswise. <http://www.newswise.com/articles/view/526667/> (January 2007).
Ruvanee Pietersz Vilhauer, Ph.D.