Accidentally Taking An Extra Dose Of Effexor XR

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Taking one extra dose of Effexor XR (venlafaxine extended-release) is not likely to cause any significant adverse reactions.

While the maximum daily dose of Effexor is 225mg per day, the information we have regarding overdosing on Effexor suggests that symptoms are relatively mild and large quantities of the drug need to be ingested to display symptoms.

Per the prescribing information for Effexor XR:

"Somnolence was the most commonly reported symptom [of overdose]. Among the other reported symptoms were paresthesia of all four limbs, moderate dizziness, nausea, numb hands and feet, and hot-cold spells 5 days after the overdose. In most cases, no signs or symptoms were associated with overdose. The majority of the reports involved ingestion in which the total dose of venlafaxine taken was estimated to be no more than several-fold higher than the usual therapeutic dose"

While accidentally taking an extra dose of Effexor XR is unlikely to cause adverse events, there are cases of significant adverse reactions to large overdoses. Symptoms include:

• Tachycardia
• Changes in the level of consciousness 
• Pupil dilations
• Seizures
• Vomiting
• Electrocardiogram changes
• Ventricular tachycardia
• Bradycardia
• Low blood pressure
• Rhabdomyolysis
• Vertigo
• Serotonin syndrome

So, what is considered a large overdose?

Several studies have detailed reports of overdosing on venlafaxine, and most suggest that it takes over 2,000mg to have significant side effects, and over 8,000mg to have cardiac toxicity-related side effects.

The most likely thing to happen after taking one extra Effexor XR dose is stomach pain and nausea.

However, if you feel you are having more serious symptoms, it would be prudent to contact poison control at 1-800-222-1222 or seek emergency medical attention.