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Venlafaxine

Brands and Forms

  • Effexor XR
    • extended-release capsule: 37.5mg, 75mg, 150mg
  • Effexor
    • tablet: 25mg scored, 37.5mg scored, 50mg scored, 75mg scored, 100mg scored

Uses of Venlafaxine

Venlafaxine is commonly used for treating Depressive Disorders (including Major Depressive Disorder, Dysthymia, and Premenstrual Dysphoric Disorder) and Anxiety Disorders (including Panic Disorder, Generalized Anxiety Disorder, Social Phobia, PTSD, and Obsessive-Compulsive Disorder).

It can also be used for treating Bulemia Nervosa, Binge-Eating Disorder, Hypochondriasis, Body Dysmorphic Disorder, Trichotillomania, Depression in Bipolar Disorder, and impulsive behaviors associated with Borderline Personality Disorder and Dementia.

How Venlafaxine Works

Venlafaxine is is a serotonin and noradrenaline reuptake inhibitor (SNRI). It boosts the actions of serotonin and norepinephrine in the central nervous system, and has similar effects on dopamine. The norepinephrine effects become more pronounced at doses above 225mg/day, and the dopaminergic effects become more pronounced at doses above 375mg/day.

Cautions when Using Venlafaxine

Venlafaxine can induce Manic or Mixed Episodes and Rapid Cycling in people with Bipolar Disorder.

Children and adolescents who use antidepressants like Venlafaxine may develop self-injurious or suicidal behaviors (for more information, see here).

Use with caution in people with a known seizure disorder, and in those who are taking anticoagulant (blood thinning) medication.

Long-term use of Venlafaxine may lead to an increased risk of osteoporosis and bone fractures in individuals over age 50.

Venlafaxine should not be used during or within 14 days following the administration of an MAOI, because a hypertensive crisis may result.

Dosing of Venlafaxine

The usual therapeutic dose range of Venlafaxine is 75-375mg/day. At doses below 225mg/day it tends to have an effect mainly on the serotonin system, whereas additional effects on the norepinephrine system occur at doses above 225mg/day. In rare cases, doses of up to 600mg/day can be used. At doses above 375mg/day there may be more pronounced dopaminergic effects.

Effexor XR is the more commonly used form of this medication, as it can be given once daily, usually in the morning. Effexor is given twice daily.

Venlafaxine is usually started at 37.5mg/day for the first week, and then increased to 75mg/day. At that point, it is recommended to wait about 4 weeks for therapeutic effects to take place before deciding to increase the dose. Dose increases are usually done in 37.5-75mg increments at 2-week intervals to allow time for therapeutic effects to appear.

When wanting to stop this medication, the dose should be decreased gradually over a period of 6-8 weeks. A sudden cessation of the medication can result in an SSRI discontinuation syndrome.

Onset of action

Therapeutic effects are not expected before 2-4 weeks. If no significant effects are seen after 6-8 weeks of use, including at least two weeks at doses above 150mg/day, then the medication may not work at all.

Kidney impairment

Lower the dose by 25-50%. Patients on dialysis should not receive subsequent dose until dialysis is completed.

Liver impairment

Lower dose by 50%.

Side-effects of Venlafaxine

 

Below is a list of most of the reported side-effects of Venlafaxine. Most of these side-effects occur in only a minority of individuals, and many also resolve with time while the medication is continued.

Cardiovascular: palpitations; hot flushes; increased blood pressure; tachycardia; orthostatic hypotension; fainting; seizures (rare).

Central Nervous System: headache; dizziness; insomnia; somnolence; fatigue; tremor; decreased libido in men (see below on managing sexual side-effects); abnormal dreams; paresthesia; weakness; disturbance in attention; convulsions; extrapyramidal symptoms (rare) ; serotonin syndrome (rare).

Dermatologic: excessive sweating; rash; hair loss (rare).

Endocrine/Metabolic: decreased appetite; decreased weight; increased total cholesterol; increased fasting triglycerides; increased LDL; SIADH; increased blood prolactin.

Eyes, Ears, Nose and Throat: pupillary dilation; blurred vision; tinnitus.

Gastrointestinal: nausea; dry mouth; constipation; diarrhea; vomiting; abnormal liver function tests.

Genitourinary: erectile dysfunction (see below on managing sexual side-effects); absent or abnormal orgasm; proteinuria; ejaculation disorder; urinary hesitation.

Hematologic: increases bleeding time (thins the blood).

Psychiatric: anxiety; agitation; irritability; apathy; worsening depression; depersonalization; suicidal thoughts (overall, Venlafaxine use helps to lower risk of suicide); self-injurious behaviors among children and adolescents; can induce Manic or Mixed Episodes and Rapid Cycling in people with Bipolar Disorder.

Common side-effects of Venlafaxine

Headache, dizziness, insomnia, somnolence, fatigue, tremor, excessive sweating, nausea, dry mouth, constipation, diarrhea, sexual dysfunction (see below on managing sexual side-effects).

Rare but serious side-effects of note of Venlafaxine

Children and adolescents who use antidepressants like Venlafaxine may develop self-injurious or suicidal behaviors (for more information, see here).

Venlafaxine discontinuation syndrome

Individuals who suddenly stop using Venlafaxine after taking the medication over a significant period of time are at risk of developing a discontinuation syndrome, which can include the following symptoms: dizziness, electric shock-like sensations, sweating, nausea, insomnia, tremor, anxiety, restlessness, agitation, depressed mood, irritability, confusion, lethargy, and vertigo. These symptoms usually start anywhere from one day to one week after the medication was stopped, and can persists for days or even weeks.

This syndrome can be treated by restarting the medication at its prior dose. It can be prevented by decreasing the dose gradually over a period of 6-8 weeks.

For individuals with severe problems discontinuing the medication, one option is to reduce the dose by 1% every 3 days. This is done by crushing the tablet of Effexor or breaking the capsule of Effexor XR and mixing this into 100ml of fruit juice. 1ml of the juice is then removed and the rest is drunk. After 3 days, 2ml of the juice is removed, and so on.

Managing sexual side-effects of Venlafaxine

In a minority of individuals, Venlafaxine can cause sexual side-effects including erectile dysfunction, absent or abnormal orgasm, and ejaculation disorder. To manage this, either Bupropion, or Sildenafil (Viagra) or Vardenafil (Levitra), can be added [ref]. (Sildenafil and Vardenafil can be effective for female sexual side-effects as well, including difficulty achieving orgasm [ref, ref]). Use caution when combining Bupropion with Venlafaxine given the risk of increased blood pressure.

Bupropion and Mirtazepine are two antidepressants that tend to have very low rates of sexual side-effects.

Venlafaxine overdose

Agitation, constipation, diarrhea, dizziness, dry mouth, headache, nausea, paresthesia, tachycardia, vomiting, seizures. Fatalities have been reported following overdoses with Venlafaxine.

Venlafaxine and pregnancy

Category C: some animal studies show adverse effects at very high doses, but no controlled human studies have been done; should only be used in pregnancy if clearly needed and if benefits outweigh potential risks. For further information, see the section on treating Depression in pregnancy.

Drug Interactions with Venlafaxine

  • Caution should be used when combining Venlafaxine with other medications that can increase bleeding time and reduce blood clotting, including Aspirin, NSAIDs, anti-platelet agents, Heparin and Coumadin.
  • Combination with other serotonergic medications, including SSRI medications, can precipitate a serotonin syndrome.
  • Venlafaxine should not be used during or within 14 days following the administration of an MAOI, because a hypertensive crisis may result.