Accidentally Taking An Extra Dose Of Effexor XR

In our latest question and answer, the pharmacist discusses what to expect if you accidentally take one extra dose of Effexor XR (venlafaxine extended-release).

Question

I think I just took 2 of my Effexor XR, which are 150mg each. One earlier and one just now. I forgot if I took it so I took another one. So I took 300mg. Is that safe? They are extended-release capsules.

Asked by Joan On Jun 17, 2022

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Jun 17, 2022
Last updated Mar 28, 2024

Key points

  • Accidentally taking one extra dose of Effexor XR is unlikely to cause significant side effects, but the risk of serious reactions varies by person.
  • The most likely side effects experienced after taking an extra dose include nausea, dizziness, and stomach pain.
  • It's never a bad idea to contact the Poison Control Center at 1-800-222-1222 if you suspect an overdose has occurred, as they can provide more specific guidance for you.

Thanks for reaching out to us!

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.

References

  • Effexor XR Prescribing Information, AccessFDA
  • Relative toxicity of venlafaxine and selective serotonin reuptake inhibitors in overdose compared to tricyclic antidepressants, PubMed

About the Pharmacist

Dr. Brian Staiger, PharmD

Dr. Brian has been practicing pharmacy for over 13 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical, program development, and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication-related questions! Dr. Brian Staiger also has herbalist training and educational certificates in the field of medical ethnobotany. Feel free to send him an email at [email protected]! You can also connect with Dr. Brian Staiger on LinkedIn.

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