Venlafaxine - Venlafaxine side effects, Dosage, Contraindications & Overdose Symptoms

Venlafaxine which is available under the brand names Effexor and Efexor is an arylalkanolamine serotonin-norepinephrine reuptake inhibitor (SNRI) which has a similar chemical structure to the opioid derivative tramadol. It is very effective in treating depression in heroin and other opioid addicts compared to all other conventional anti-depressants.
It is licensed for the treatment of major depressive disorder (MDD), as a treatment for generalized anxiety disorder, and comorbid indications in certain anxiety disorders with depression. It is not reported that venlafaxine like other anti-depressants has a potential to increase suicidal thoughts, attempts and events of self-harm in children and adolescents.

Availability And Packaging

Venlafaxine is available as Generic Effexor tablets and Effexor XR capsules. Generic Effexor is available as tablets which are pentagon shaped and peach colored in 25 mg, 37.5 mg, 50 mg, 75 mg, and 100 mg. It is also distributed as Generic Effexor XR Capsules (extended release version) 37.5 mg, 75 mg and 150 mg capsules.

Effexor XR  CapsulesView Of 75mg and 150mg Effexor XR Capsules


Venlafaxine is used primarily for the treatment of major depression in adults. Venlafaxine has similar efficacy to the tricyclic antidepressants amitriptyline (Elavil) and imipramine and is better tolerated than amitriptyline.
Its efficacy is similar to or better than sertraline (Zoloft) and fluoxetine (Prozac), depending on the criteria and rating scales used. Higher doses of venlafaxine are more effective, and more patients achieved remission or were "very much improved".

Venlafaxine - Contraindications

Venlafaxine is contraindicated in children and adolescents because it can increase suicidal thoughts, attempts, and self-harm . In addition to this studies of venlafaxine in these age groups have not established its efficacy or safety.
Venlafaxine is not recommended in patients hypersensitive to venlafaxine. It should not be taken by anyone who is allergic to the inactive ingredients, which include gelatin, cellulose, ethylcellulose, iron oxide, titanium dioxide and hypromellose. It should never be used with a monoamine oxidase inhibitor (MAOI), as it can cause potentially deadly serotonin syndrome. At least 14 days must pass between the use of venlafaxine and MAO inhibitors. Caution should also be used in those with a seizure disorder.
Venlafaxine can increase eye pressure, so those with glaucoma may require more frequent eye checks. Venlafaxine should only be used during pregnancy if clearly needed.Studies have not shown any statistically significant congenital malformations. There have, however, been some reports of self-limiting effects on newborn infants. Venlafaxine use during pregnancy increases the risk of spontaneous abortion.

Side effects of Venlafaxine

Various side effects have been noted in patients during the clinical trials of Venlafaxine. Below are listed the main side effects together with the percentage of patients that displayed them during the clinical trials in brackets.

  • Headache (34%)
  • Nausea (21-35%)
  • Insomnia (15-23%)
  • Sexual dysfunction (14-34%)
  • Dry mouth (12-16%)
  • Dizziness (11-20%)
  • Sweating (10-14%)
  • Decreased Appetite (8-20%)
  • Abnormal ejaculation (8-16%)
  • Hypertension (4-5%)
  • Vivid/Abnormal dreams (3-7%)
  • Akathisia (Agitation) (3-4%)
  • Decreased libido (3-9%)
  • Increased yawning (3-5%)
  • Apathy
  • Constipation
  • Ongoing Irritable Bowel Syndrome
  • Fatigue
  • Vertigo
  • Orthostatic hypotension (postural drop in blood pressure)
  • Impulsive Actions
  • Electric shock-like sensations also called "Brain zaps"
  • Increased anxiety at the start of treatment
  • Memory Loss
  • Restless Legs Syndrome

There are less commonly occuring to rarely occuring side-effects in patients taking this drug. They include Cardiac arrhythmia, Increased serum cholesterol, Gas or stomach pain, Abnormal vision, Nervousness, agitation or increased anxiety, Panic Attacks, Depressed feelings, Suicidal thoughts, Confusion, Neuroleptic malignant syndrome.
The other side effects include Tremor, Drowsiness, Allergic skin reactions, External bleeding, Serious bone marrow damage (thrombocytopenia, agranulocytosis), Hepatitis, Pancreatitis, Seizure, Tardive dyskinesia, Dysphagia (difficulty swallowing), Psychosis, Hair Loss, Hostility, Activation of mania/hypomania, Weight Loss, Weight gain, Homicidal thoughts, Aggression, Depersonalization, Visual Hallucinations, Swollen and/or bleeding gums and Frequent urination.

Venlafaxine (Effexor XR) Dosage

The recommended starting dose for Effexor XR is 75 mg/day, in case of most patients, administered in a single dose. Effexor XR is administered in a single dose with food at approximately the same time each day.

Venlafaxine Overdose Symptoms

Most patients overdosing with venlafaxine develop only mild symptoms. However, severe toxicity is reported with the most common symptoms being CNS depression, serotonin toxicity, seizure, or cardiac conduction abnormalities.
Venlafaxine's toxicity appears to be higher than other SSRIs, with a fatal toxic dose closer to that of the tricyclic antidepressants than the SSRIs. Doses of 900 mg or more are likely to cause moderate toxicity. Deaths have been reported following very large doses.

Additional Information

Manufacturers pamphlet:

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