People have reported feeling electric shock-like sensations or “brain zaps” when starting Cymbalta (duloxetine) treatment, during treatment, and also when discontinuing it. Most report feeling these in the brain although some report them in other parts of the body. They have been described as feeling like a short, low voltage, electric shock.

The zaps or electric shocks associated with Cymbalta last momentarily to a few seconds. They usually happen without warning and their frequency varies from a couple per minute to once every few hours or days, with periods of calmness or no abnormal sensations in between. The shocks are not accompanied by any muscle spasms. The duration of the shocks last from days to weeks.

The medical term for this is central paresthesia (paraesthesia means any odd sensation, such as a burning, prickling, tingling, itching, numbness, or skin-crawling sensation that is felt in the body).

The Pharmacovigilance Centre in the Netherlands describes 5 cases of electric shock sensations occurring with Cymbalta: 2 on starting the drug, 2 on discontinuing it, and one patient reported the sensations at the start of treatment and after an unintentionally missed dose. Significant aspects of the report include:

• Patient A: Electric shocks occurred when the dose was reduced from 60mg after 11 months of treatment to 30mg
• Patient B: Electric shock sensations occurred one day after each dose reduction and persisted for 3 days – this patient also developed an unspecified thyroid disorder during the discontinuation of duloxetine
• Patient C: Electric shocks occurred through the head, particularly when turning the head and during walking on a solid floor. Sometimes the shocks were painful. The patient had similar electric shock sensations in the past during the withdrawal of paroxetine
• Patient D: Electric shocks and also anxiety attacks, emotional instability, enhanced memories, myoclonus, dry mouth, and fatigue occurred during the start of treatment
• Patient E: Electric shocks in addition to headache, insomnia, constipation, and restless legs following treatment with duloxetine

All 5 patients used recommended doses of duloxetine. In four patients, the electric shock sensations were localized in the brain and one patient, in the extremities. At the time of this report, 3 patients had recovered and 2 had not.

What causes brain zaps with Cymbalta?

Nobody knows why some people experience brain zaps or electric shock sensations with Cymbalta. They are listed as a very rare side effect (less than 0.01%) in the product information.

How can you stop brain zaps with Cymbalta?

Brain zaps or electric shock sensations with Cymbalta are likely to go away by themselves within a few days or weeks. If they don't, and you haven't discontinued the drug, contact your doctor for more advice. There is currently no known treatment, but Cymbalta should be discontinued if they persist and you are still taking Cymbalta.

Are electric shock sensations common?

Electric shock-like sensations or “zaps” have also been reported with other antidepressants, such as SSRIs (including paroxetine, fluoxetine, and citalopram), at the start of, during, and on treatment discontinuation.