Effexor

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Effexor Description:

Effexor (venlafaxine hydrochloride) is a synthetic derivative of phenthylamine and a prescription antidepressant first marketed by Wyeth in 1993 under the names Effexor (tablets) and Effexor XR (extended-release). Since the drug is currently under patent, a generic will not be available until 2008 in America, and the European patent will hold until 2017.

Venlafaxine is used in treating panic disorder, generalized anxiety disorder (GAD), social anxiety disorder (SAD; social phobia), and depression.

Classification:

Antidepressant

Clinical Pharmacology:

The mechanism of action in humans is thought to be associated with its potentiation of neurotransmitter activity in the central nervous system. Preclinical studies have shown Venlafaxine and its active metabolite to be potent inhibitors of serotonin and norepinephrine reuptake and weak inhibitors of dopamine reuptake.

Indications and Dosage:

Effexor is indicated for treating major depressive disorder. A major depressive episode implies persistent depressed or dysphoric mood that usually interferes with daily functioning – nearly everyday for at least 2 weeks.

The recommended initial dosage for Effexor is 75mg/day, given in two or three divided doses with food. Depending on tolerability and the need for further clinical effect, the dose may be increased to 150mg/day, increased further to 225mg/day if needed.

When raising dosages, incremental increases of up to 75mg/day should be made in intervals of no less than 4 days. In outpatient settings, there was no evidence of efficacy in doses greater than 225mg/day for moderately depressed persons, but more severely depressed inpatients responded to a mean dose of 350mg/day. Certain patients, including more severely depressed patients, may then respond to even higher doses, up to a maximum of 375mg/day, normally in three divided doses.

Side Effects and Interactions:

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The most frequent side effects of Effexor use include somnolence, nervousness, insomnia, dizziness, dry mouth, anxiety, changes in urination, fatigue, vertigo, vivid dreams, electric-shock like sensations, increased blood pressure, gastrointestinal distress, nausea, headache, asthenia, sweating, and abnormal ejaculation/orgasm/impotence in men.

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Rare to abnormal side effects may include cardiac arrhythmia, gas/stomach pain, abnormal vision, increased serum cholesterol, nervousness, agitation or increased anxiety, feelings of depression, confusion, loss of appetite, constipation, tremor, drowsiness, neuroleptic malignant syndrome, adverse skin allergies, external bleeding, serious bone marrow damage, hepatitis, pancreatitis, seizures, tardive dyskinesia, and difficulty swallowing.

Information for Parents and Kids:

According to recent testing, Effexor should not be administered to children under age 18. Clinical tests showed children had no benefit from Effexor in treating childhood depression, but did show an increase in adverse outcomes, including at least twice as many reports of hostility, episodes of self-harm and suicidal thoughts.

If your children are using Effexor, do not abruptly cease the medication; rather, discuss options with your child’s physician.

Warnings and Precautions:

For people taking MAO Inhibitors, the addition of buspirone may pose a health hazard. Reports of elevated blood pressure have occurred. It is therefore recommended that buspirone not be used with an MAOI.

Patients with major depressive disorder (MDD), both adult and pediatric, may experience worsening of the depression or the emergence of suicidality in behavior and thought, or unusual changes in behavior, whether taking antidepressants or not. Antidepressants have been shown to increase the risk of suicidal thinking and behavior in short-term studies in children and teenagers with MDD and other psychiatric disorders.

All pediatric patients being treated with antidepressants for any reason should be closely observed for clinical worsening, unusual changes in behavior, and suicidality, especially during the first few months of treatment, or with changes in dosage

Withdrawal:

Venlafaxine is rather notorious for its potentially severe withdrawal symptoms upon sudden cessation (the recommended discontinuation is a decrease of 37.5mg/week; sudden discontinuation is recommended only in emergencies). These have a tendency to be significantly stronger than withdrawal effects of other antidepressants including tricyclics, but are similar to those of SSRIs such as Paxil.

Withdrawal effects may include headache, nausea, fatigue, dysphoria, “brain shivers”, irritability, and hostility. Symptoms exhibited with more rarity include tremors, shaking legs, vertigo, paresthesia, and dizziness. Other symptoms can include impaired concentration, bizarre dreams, agitation and suicidal thoughts.

Addictive effects are not indicated in withdrawal, but are rather the results of the brain attempting to reach neurochemical stability after an abrupt change. Such effects can be minimalized or avoided by tapering off of the medication over a period of weeks.

Studies conducted by Wyeth-Ayerst Laboratories and others have reported occasional cases of withdrawal symptoms severe enough to require permanent use. In some of these instances, the medication was successfully discontinued eventually with the addition of fluoxetine, which was later itself discontinued without difficulty.

Over-dosage & Contraindications:

An overdose of Effexor, in combination with other drugs or alcohol, may be fatal. Symptoms of Effexor overdose include vertigo, dizziness, nausea, numbness/tingling in the hands or feet, sleepiness, rapid or slow heartbeat, low blood pressure, seizures, or coma.

Venlafaxine contraindications may include hypersensitivity to Venlafaxine hydrochloride and concomitant use in those taking MAOIs is contraindicated. Reports have shown that serious, sometimes fatal reactions may occur in patients receiving antidepressants with pharmacological properties similar to Venlafaxine in combination with MAOIs. Therefore, Effexor should not be used in conjunction with MAO inhibitors or within two weeks of ceasing treatment with MAOIs. In the same fashion, MAOI treatment should not begin until two weeks after discontinuation of Effexor.

Generic Name: venlafaxine

Chemical Formula: C17H27NO2

Routes of Administration: oral

Elimination Half Life: approximately 5 hours

Legal Status: by prescription only

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