Effexor side effects: Effexor is a brand of the SNRI (serotonin-norepinephrine reabsorption inhibitor) antidepressant generic name venlafaxine. Effexor is indicated for therapy of major depressive disorder and is available in immediate release dosage forms of 25 mg, 37.5 mg, 50 mg, 75 mg, and 100 mg. Effexor XR is available in 37.5 mg, 75 mg, and 150 mg capsules. Most patients prefer using extended-release Effexor product because of the once a day ease of administration especially because immediate release Effexor often used be dose three times a day. Effexor has a major drawback in its very short-term half-life of 46 hours and Effexor withdrawal side effects are very common on Effexor discontinuation.
Black box warning: Effexor, like most of the SSRI and SNRI antidepressants carries a black box warning of increased risk of suicide in patients under 25 years old. The risk of suicide in patients over 65 is probably actually decreased with effects of therapy and in patients from 25 to 64 years old the incidence of suicide is probably not changed by therapy. When Effexor is used in patients under age 25 families need to be advised for the need for careful observation and communication with the prescribing physician. Effexor is not approved for pediatric use.
Common Effexor side effects: the list of common Effexor side effects is extensive and includes numerous gastrointestinal and central nervous system side effects. The G.I. Effexor side effects can include nausea, constipation, diarrhea, vomiting, and weight loss. The central nervous system Effexor side effects that are common include headache, insomnia, somnolence, nervousness, loss of appetite, blurry vision, anxiety, tremor, abnormal dreams and excessive yawning. Other potential common Effexor side effects include dizziness, sweating, anorgasmia and delayed or abnormal ejaculation, erectile dysfunction, hypercholesterolemia, a pins and needles sensation called paresthesias, increased heart rate, high blood pressure, rash and infection.
Serious Effexor side effects: worsening depression and risk of suicidality as mentioned in the black box warning above is a serious Effexor side effect. One of the more common major and potentially serious Effexor side effects is the Effexor withdrawal syndrome or discontinuation syndrome. This can be very bothersome and include dizziness, lightheadedness and on electric like shock sensations in the head and neck. Unmasking of the mania of bipolar disorder is a potential serious Effexor side effect. Other potential serious Effexor side effects include the serotonin syndrome, neuroleptic malignant syndrome, high blood pressure, seizures, cardiac arrhythmias, low serum sodium sometimes from SIADH, pancreatitis, glaucoma, serious blood dyscrasias, and extrapyramidal symptoms. Allergic or hypersensitivity reactions can include interstitial lung disease, eosinophilic pneumonia, and anaphylaxis as well as other severe skin reactions.
Cautions contraindications and drug interactions: Effexor is contraindicated course in patients with known hypersensitivity to Effexor or drugs in its class. Effexor should be discontinued gradually to avoid Effexor withdrawal syndrome. Caution is advised for use in patients under age 25. Caution is also advised for use in patients with a seizure disorder, history of mania, and suicidal patients, in patients with high blood pressure or elderly patients, in patients who are dehydrated, in patients with low serum sodium, patients with angle closure glaucoma or other causes intraocular pressure, in patients with hyperthyroidism or heart failure as well as recent myocardial infarction. Caution is advised for use in late pregnancy and in patients with significant renal insufficiency. The list of file medications with potential drug interactions is extensive and only some of the more commonly used or serious drug interactions are mentioned here. For specific medication drug interactions patient should discuss the issues with their physician or pharmacist and for complete list of potential drug interactions refer to the manufacturers prescribing guidelines. Only some of the more common issues are discussed here for the sake of brevity.
Effexor is contraindicated for use with the nonselective MAO inhibitors, the phenothiazines, and cisapride. Alternative medications should be used when possible in patients on the migraine headache medications known as the triptans like Imitrex and others, amiodarone, all of the other SSRIs and SNRIs, erythromycin, methadone, St. John’s wort, and quinine sulfate. Modification of therapy may be needed with carbamazepine, cisplatin, most of the NSAIDs, ondansetron, trazodone, tricyclic antidepressants, warfarin and the sulfonylureas. Caution is advised for use with aspirin, other antiplatelet agents, dextromethorphan, yohimbine, tramadol, risperidone, and pharmacologic doses of omega-3 acids.
Pregnancy and lactation: Effexor is considered pregnancy category C with a special concern overlay trimester use because of the potential for Effexor discontinuation syndrome in the neonate. The safety of Effexor in lactation is uncertain. During pregnancy abrupt discontinuation of Effexor is not advised and the medication should be gradually tapered to avoid discontinuation syndrome symptoms.
Pharmacology: Effexor is extensively metabolized in the liver using the CYP 450 metabolic pathway especially as a 2D6 substrate. Effexor is largely excreted in the urine all low mostly after hepatic metabolism. Serum half-life is five hours for venlafaxine and 11 hours for the metabolite O-desmethylvenlafaxine.
Recently venlafaxine is become available as a generic product making it more affordable for some patients. Some providers are reluctant to use Effexor because of the difficulty with the Effexor discontinuation syndrome as well as concerns about high blood pressure management in patients on Effexor.
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