Antidepressants work by helping to balance natural chemicals in the brain called neurotransmitters, according to the National Institute of Mental Health. This may result in improved moods for many patients with depression and anxiety disorders. Selective serotonin reuptake inhibitors, known as SSRIs, appear to focus only on serotonin neurotransmitters that affect emotions. Other drugs may influence serotonin and other chemicals. Serotonin and norepinephrine reuptake inhibitors, for example, work on serotonin and the adrenal hormone norepinephrine.
Function
Although the detailed workings of SSRIs are not completely clear, research indicates the drugs manage to block the reabsorption or reuptake of serotonin by nerve cells in the brain, MayoClinic.com explains. The cells normally absorb serotonin after the chemical performs a function. By blocking reuptake, SSRIs leave more serotonin in the brain to enhance neurotransmission and improve moods.
Influence
Antidepressants that affect serotonin influence the brain in other ways, as well. They may help nerve cells maintain proper levels of glutamate, a compound of a nonessential amino acid. This prevents glutamate from stimulating brain areas related to depression and anxiety. SSRIs and other antidepressants also affect people in different ways. The response may depend on a patient's particular serotonin functioning, which may differ among people. Some patients need to experiment with more than one antidepressant before finding the correct medication.
Types
SSRIs available for depression and anxiety include fluoxetine, citalopram, sertraline, paroxetine and escitalopram. Doctors may prescribe a combination of fluoxetine and olanzapine to treat bipolar depression, a condition that causes extreme mood swings from unusual excitement to depression. Olanzapine falls into the category of SSRI and atypical antipsychotic, MayoClinic.com notes.
Side Effects
Doctors often prescribe SSRIs as a first choice of treatment because of advantages that include fewer side effects than other antidepressants. Like other medications, however, SSRIs may produce side effects in some patients. Nausea, dry mouth, headaches, nervousness, agitation, weight gain, insomnia, drowsiness, rash and diarrhea may occur. The symptoms often subside after using the drug for a few weeks. Doctors may adjust the dosage to ease side effects. SSRIs have a high rate of sexual side effects that cause reduced desire or sexual difficulties. Patients may benefit from a second antidepressant that reduces the effects or an added sexual enhancement drug to help avoid the problem.
Serotonin Syndrome Warning
High levels of serotonin in the brain can cause life-threatening situations from use of SSRIs and other medications, according to MayoClinic.com. SSRIs can interact with another antidepressant called monoamine oxidase inhibitors, or MAOIs. The two drugs should not be taken within two weeks of each other. SSRIs may also adversely interact with certain pain relief or migraine medications and supplements that affect serotonin levels. Dangerous interactions may result in serotonin syndrome, leading to confusion, hallucinations, extreme agitation, increased heart rate, nausea, seizures and coma. The symptoms require immediate medical treatment.
