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- What is venlafaxine, and how does it work (mechanism of action)?
- What brand names are available for venlafaxine?
- Is venlafaxine available as a generic drug?
- Do I need a prescription for venlafaxine?
- What are the side effects of venlafaxine?
- What is the dosage for venlafaxine?
- Which drugs or supplements interact with venlafaxine?
- Is venlafaxine safe to take if I'm pregnant or breastfeeding?
- What else should I know about venlafaxine?
What is venlafaxine, and how does it work (mechanism of action)?
Venlafaxine is a selective serotonin and norepinephrine reuptake inhibitor (SNRI) used for treating depression. Other drugs in this class include milnacipran (Savella), duloxetine (Cymbalta), and desvenlafaxine (Pristiq). Venlafaxine affects neurotransmitters, the chemicals that nerves within the brain make and release in order to communicate with one another. Neurotransmitters either travel across the space between nerves, attach to receptors on the surface of nearby nerves, or they attach to receptors on the surface of the nerves that produced them, to be taken up by the nerve and released again (a process referred to as re-uptake).
Many experts believe that an imbalance among neurotransmitters is the cause of depression as well as other psychiatric disorders. Serotonin and norepinephrine are two neurotransmitters released by nerves in the brain. Venlafaxine works by preventing the reuptake of serotonin and epinephrine by nerves after they have been released. Since uptake is an important mechanism for removing released neurotransmitters and terminating their actions on adjacent nerves, the reduced uptake caused by venlafaxine increases the effect of serotonin and norepinephrine in the brain. Venlafaxine is available in an extended release formulation (Effexor XR). The FDA approved venlafaxine in December 1993.
What are the side effects of venlafaxine?
Venlafaxine, like most anti-depressants, can cause:
Other side effects that can occur are:
Increased blood pressure can occur, and blood pressure should be monitored.
Seizures have been reported.
The FDA suggests if anti-depressants are discontinued abruptly, symptoms may occur such as dizziness, headache, nausea, changes in mood, or changes in the sense of smell, taste, etc. (Such symptoms even may occur when even a few doses of anti-depressant are missed.) Therefore, it is generally recommended that the dose of anti-depressant be reduced gradually when therapy is discontinued.
Antidepressants increased the risk of suicidal thinking and behavior (suicidality) in short-term studies in children, adolescents, and young adults with depression and other psychiatric disorders. Anyone considering the use of venlafaxine or any other antidepressant in a child or adolescent must balance this risk with the clinical need. Patients who are started on therapy should be closely observed for clinical worsening, suicidality, or unusual changes in behavior.
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What is the dosage for venlafaxine?
Venlafaxine should be taken with food at doses specifically directed by a physician. Individual doses vary greatly among individuals. The anti-depressant effects are not maximal for 1-2 weeks. If discontinued, the dose of venlafaxine should gradually be reduced under the direction of a physician. For patients with difficulty swallowing tablets or capsules, capsules of Effexor XR can be opened and the contents sprinkled on a spoonful of applesauce but removal from the capsule allows immediate release of the drug so it is no longer an extended release drug.
The dose for treatment of depression using the immediate release formulation is 75 to 375 mg daily divided in 2 or 3 doses and given every 8 or 12 hours. The extended release dose is 37.5 mg to 225 mg once daily. Dosing is usually begun with low initial concentrations and adjusted as needed by the treating doctor.
Generalized anxiety and panic disorder are treated with 37.5 mg to 225 mg once daily using the extended release formulation. Social anxiety is treated with 75 mg daily using the extended release formulation.
Which drugs or supplements interact with venlafaxine?
Venlafaxine should not be used in combination with a monoamine oxidase inhibitor (MAOI) such as phenelzine (Nardil), tranylcypromine (Parnate), isocarboxazid (Marplan), and selegiline (Eldepryl), or within 14 days of discontinuing the MAOI. At least 5 days should be allowed after stopping venlafaxine before starting an MAOI. Combinations of SNRIs and MAOIs may lead to serious, sometimes fatal, reactions including very high body temperature, muscle rigidity, rapid fluctuations of heart rate and blood pressure, extreme agitation progressing to delirium, and coma. Similar reactions may occur if venlafaxine is combined with antipsychotics, tricyclic antidepressants or other drugs that affect serotonin in the brain. Examples include tryptophan, sumatriptan (Imitrex), lithium, linezolid (Zyvox), tramadol (Ultram), and St. John's Wort.
Combining venlafaxine with aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), warfarin (Coumadin) or other drugs that are associated with bleeding may increase the risk of bleeding, because venlafaxine is associated with bleeding.
Most medications affecting the brain such as venlafaxine have the potential to slow reflexes or impair judgment. Therefore, caution is advised especially early in the course of treatment.
Safety has not been established in children below the age of 18 years.
Is venlafaxine safe to take if I'm pregnant or breastfeeding?
The effects of venlafaxine on the fetus during pregnancy are unknown.
It is not known if venlafaxine is secreted in breast milk, and therefore, if it may have an effect on nursing infants.
What else should I know about venlafaxine?
What preparations of venlafaxine are available?
- Tablets: 25, 37.5, 50, 75, and 100 mg.
- Tablets (Extended Release): 37.5, 75, 150, 225 mg;
- Capsules (Extended Release): 37.5, 75, and 150 mg.
How should I keep venlafaxine stored?
Store in a dry place at 20 C to 25 C (68 F to 77 F).
Reference: FDA Prescribing Information
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