In order for an antidepressant medication to be marketed in the United States, it must receive approval from the U.S. Food & Drug Administration. This usually follows extensive clinical trials in which people suffering from depression take the medication alongside another group of people taking a placebo. The patients in the studies do not know whether they take the placebo or the real drug. When the effectiveness of the drug reaches a certain, predictable level, the FDA approves the medication for marketing.
Fluoxetine
Categorized as an SSRI or selective serotonin reuptake inhibitor, fluoxetine helps reduce the symptoms of depression by actions in the brain. The drug essentially makes the neurotransmitter serotonin more active by preventing the brain from reabsorbing it too quickly. Since fluoxetine came on the market in 1987, several other SSRIs have been developed. The most common serious side effects of this medicine include restlessness and a skin rash, but the most commonly associated side effect of a lowered libido also may occur. In this case, the sexual side effect should cease without medical help.
Venlafaxine
SNRIs or selective serotonin and norepinephrine reuptake inhibitors such as venlafaxine work much the same way as SSRIs with the added action of preventing too much norepinephrine, also a neurotransmitter, from reabsorbing in the brain. While researchers do not know exactly why such medications affect and treat depression, MayoClinic.com reports, these drugs seem to work better than older antidepressants and have fewer side effects. Some of the more common and temporary nonserious side effects of venlafaxine include anxiety, less interest in sex, nausea, insomnia and blurry vision.
Bupropion
Bupropion classifies as an NDRI or norepinephrine and dopamine reuptake inhibitor. Instead of working with serotonin, NDRIs help the person's brain work more effectively with dopamine and norepinephrine by stopping the reabsorption of these neurotransmitters. Common, nonserious side effects include constipation, weight loss, uncontrollable shaking, over-excitement and drowsiness.
Amitriptyline
Tricylic antidepressants such as amitriptyline predate SSRIs, SNRIs and NDRIs, although they work in similar ways, MayoClinic.com indicates. Tricyclics, too, help make norepinephrine and serotonin more active, but they also do the same thing with other neurotransmitters that can induce more severe side effects. Sexual problems along with blurry vision, diarrhea, appetite loss and drowsiness occur as common and nonserious side effects of amitriptyline, Drugs.com reports.
Tranylcypromine
Monoamine oxidase enzymes metabolize dopamine, serotonin and norepinephrine, which, in some people, can lead to depression. Monoamine oxidase inhibitors such as tranylcypromine stop this from happening, allowing the three neurotransmitters to remain in the brain. This, MayoClinic.com reports, helps raise the level of the mood of the person suffering from depression. The National Institutes of Health indicates such problems as bodily weakness, pain in the stomach, decreases in sexual ability and leg or arm numbness may occur as nonserious common side effects of the drug.
