Effexor is used to treat depression and belongs to a group of antidepressants called selective serotonin and norepinephrine reuptake inhibitors or SNRIs.According to MedlinePlus, Effexor increases the available amount of the brain messenger chemicals, serotonin and norepinephrine. All antidepressants have side effects and Effexor is no exception. Drugs.com reports that Effexor's most common side effects are usually mild and self-limiting, and include anxiety. somnolence, sweating, dizziness, headache, insomnia and abnormal ejaculation in men. Suicidal thoughts and behavior have been reported in children and young adults that usually occurs shortly after starting Effexor. After long-term use, several notable Effexor-related side effects are possible.
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Serotonin syndrome is a serious condition characterized by mental confusion, racing heart, fluctuating blood pressure, fever, lack of coordination and gastrointestinal symptoms of nausea, vomiting and diarrhea. The cause of this syndrome is an excess of serotonin in the body brought on by the use of drugs that raise serotonin levels, including Effexor, according to the University of Maryland Medical Encyclopedia. The risk of serotonin syndrome increases as the dose of Effexor is increased or when used with other classes of drugs that elevate serotonin levels, such as tryptophan. Treatment includes prompt discontinuation of Effexor and supportive care, often in an intensive care unit.
Drugs.com reports an association between Effexor and sustained hypertension that is dose-related. It occurs in up to 13 percent of patients taking Effexor at a dose of 300mg or higher. Before starting Effexor, pre-existing high blood pressure should be controlled. Effexor-related hypertension is usually treated by reduction of the Effexor dose or discontinuation of the drug.
RxList.com reports about 6 percent of patients taking Effexor experience weight loss. The incidence of weight loss increases with higher doses of Effexor. Effexor is not indicated for weight loss alone and the safety of using this drug in combination with weight loss agents has not been well-studied and is not recommended.
Stopping Effexor suddenly, as with other SNRIs, often results in a constellation of symptoms, including dizziness, an electric shock-type sensation, anxiety, confusion, insomina, lack of coordination, ringing in the ears as well as nausea and vomiting, according to MedlinePlus. The risk of these side effects increases with the length of time on Effexor. The adverse symptoms might be severe but are usually self-limiting. Drugs.com recommends gradually tapering off Effexor if the drug needs to be discontinued, rather than abruptly stopping it.