Understanding Antidepressant Medications
affects about 121 million people worldwide and is a leading cause of
disability, according to the World Health Organization (WHO).
my experience as a practicing psychiatrist, I've seen that many people
with depression don't realize that they have the condition or that it's
treatable," says Mitchell Mathis, M.D., deputy director of the Division
of Psychiatry Products at the Food and Drug Administration (FDA).
who suffer from depression don't recognize the symptoms, or they
attribute them to lack of sleep or a poor diet. Others realize they are
depressed, but they feel too fatigued or ashamed to seek help.
Not all depression requires treatment with medication.
have shown that the best way to treat a patient with the more severe
form of major depressive disorder is through both therapy and
prescribed antidepressant medication," Mathis says. "They work best in
combination with one another."
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Diagnosing the Disease
Medical professionals generally base a diagnosis of major depressive disorder on the presence of certain symptoms listed in the
American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Diagnosis depends on the number, severity, and duration of these symptoms:
- depressed mood
- loss of interest or pleasure in almost all activities
- changes in appetite or weight
- disturbed sleep
- slowed or restless movements
- fatigue, loss of energy
- feelings of worthlessness or excessive guilt
- trouble in thinking, concentrating, or making decisions
- recurring thoughts of death or suicide
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Types of Antidepressants
work to normalize naturally occurring brain chemicals called
neurotransmitters—primarily serotonin, norepinephrine, and dopamine.
Scientists have found that these particular chemicals are involved in
regulating a person's mood.
There are several different classifications of antidepressants:
- Selective Serotonin Reuptake Inhibitors (SSRIs): Examples are Prozac (fluoxetine), Celexa (citalopram), and Paxil (paroxetine).
- Serotonin and Norepinephrine Reuptake Inhibitors (SSNIs): Examples are Effexor (venlafaxine) and Cymbalta (duloxetine).
- Tricyclic antidepressants (TCAs): Examples are Elavil (amitriptyline), Tofranil (imipramine), and Pamelor (nortriptyline).
- Monoamine Oxidase Inhibitors (MAOIs): Examples are Nardil (phenelzine) and Parnate (tranylcypromine).
There are other antidepressants that don't fall into any of these classifications and are considered unique, such as:
- Remeron (mirtazapine)
- Wellbutrin (bupropion)
The antidepressant medications in each classification
affect different neurotransmitters in particular ways. For example,
SSRIs increase the production of serotonin in the brain. MAOIs block
monoamine oxidase, an enzyme that breaks down neurotransmitters.
Blocking their breakdown means that neurotransmitters remain active in
the brain. Research is ongoing to determine antidepressants' exact
mechanism of action on a person's brain.
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how does a physician determine which antidepressant to prescribe?
Doctors typically use a patient history and a mental status exam. With
this information, the doctor can evaluate symptoms, rule out medical
causes of depression, and decide if the criteria are met for major
"In my opinion, it's best when
antidepressant medications are personalized," says Mathis. "For
example, some depressed people have difficulty sleeping. So they would
benefit from a more sedating antidepressant at night. Other people with
depression sleep too much and would benefit from a more activating
antidepressant in the morning."
It's important to communicate how you are feeling so that your physician can evaluate the medication's effectiveness.
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Effectiveness of Antidepressants
60 to 70 percent of patients respond to the first antidepressant that
is prescribed or to an increased dosage of that drug, according to
But patients must take regular doses of a
prescribed antidepressant for at least 3 to 4 weeks before they are
likely to experience the full therapeutic effect. And if patients start
to feel better, they should not stop taking the antidepressant.
if you start to feel better, you may be in between episodes," says
Mathis. "Depression tends to be chronic and requires everyday treatment
just like high blood pressure."
If you get used to an
antidepressant and just quit it, you may experience some withdrawal
symptoms such as anxiety and irritability. Worst of all, depression may
Patients should continue taking an
antidepressant for 6 to 12 months, or in some cases longer, according
to the National Institute of Mental Health (NIMH). This gives
medication time to be effective and can help prevent a relapse of the
depression. Patients should carefully follow their doctor's
Mathis estimates that about 10 percent of depressions are treatment resistant and won't respond to prescribed antidepressants.
means that 20 to 30 percent of patients may not respond to the first
antidepressant that is prescribed for them. NIMH-funded research has
shown that patients who did not get well after taking a first
medication increased their chances of becoming symptom-free after they
switched to a different medication or added another medication to their
With appropriate treatment, many people
with depression experience improvement of their symptoms and return to
living normal and productive lives.
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Managing Side Effects
antidepressants come with Medication Guides. These guides provide
FDA-approved information for patients, families, and caregivers that
could help improve monitoring of a drug's effects. Medication Guides
are intended to be distributed at the pharmacy with each prescription
or refill of a medication.
Many people who take antidepressants have at least one side effect. Side effects can include:
- Night sweats
- Sexual problems
- Dry mouth
Side effects are the most common reason people stop
taking antidepressants. It's recommended that you don't stop taking
your antidepressants or reduce the dosage without talking to your
doctor or mental health professional first.
are coping strategies for the most common side effects of
antidepressants. For a more complete list of side effects and suggested
coping strategies, visit www.nimh.nih.gov/health/publications/medications/antidepressant-medications.shtml
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In October 2004, FDA directed manufacturers to add a boxed warning to
the labeling of all antidepressant medications to alert the public
about the increased risk of suicidal thinking or suicide attempts by
children and adolescents taking antidepressants.
boxed warning is the most serious type of warning used on prescription
drug labeling. In May 2007, FDA directed that the warning should be
extended to include young adults up through age 24.
detailed analysis by FDA of antidepressant clinical trials showed an
increased risk of suicidality—suicidal thoughts or behavior. "There
weren't more actual suicides, but more people under 24 were thinking or
talking about it," explains Mathis. "This occurs most often within the
first 30 days of an adolescent or young adult starting on an
Mania: When people are in a manic "high," they may
be overactive, overly talkative, have a great deal of energy, and need
less sleep than normal.
There are two different types of mood disorders, both of which are
cyclical. One is unipolar disorder, in which the cycle is that a person
feels normal and then feels depressed. The other type is bipolar
disorder, in which the person's mood cycles from depressed to normal to
"The doctor needs to screen patients for a bipolar history," said
Mathis. If an antidepressant is prescribed to a person with bipolar
disorder, it can cause mania. And the person can even become psychotic
if the mania is severe.
Birth Defects: In December 2005, FDA changed Paxil
(paroxetine) from a pregnancy risk category of C to D. With a Category
C drug, fetal risk can't be ruled out. With a Category D drug, positive
evidence of fetal risk exists. FDA chooses a medicine's letter category
based on what is known about the medicine when used in pregnant women
High Blood Pressure: It
can be much more difficult for patients to take one of the MAOIs for
depression because of the many dietary and medicinal restrictions that
must be followed. People taking MAOIs must avoid certain foods that
contain high levels of the chemical tyramine, which is found in many
cheeses, wines and pickles, and some medications including
decongestants. MAOIs interact with tyramine in such a way that may
cause a sharp increase in blood pressure, which could lead to a stroke
or other complications.
This article appears on FDA's Consumer Health Information Web page (www.fda.gov/consumer), which features the latest updates on FDA-regulated products. Sign up for free e-mail subscriptions at www.fda.gov/consumer/consumerenews.html.
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For More Information
Antidepressant Use in Children, Adolescents, and Adults
National Institute of Mental Health (NIMH)
Date Posted: January 9, 2009