Pacerone (amiodarone) has been linked to potentially life-threatening complications, including lung damage, liver damage, and irregular heartbeat. The medication should only be used when its benefits outweigh its risks.

What is Pacerone?

Pacerone (amiodarone) is an anti-arrhythmic drug developed by Upsher-Smith Laboratories to treat ventricular arrhythmias. This is a severe type of irregular heartbeat that occurs in the two lower chambers of the heart. Because of the complications associated with Pacerone, the medication is only to be used as a last resort “to treat adults with life-threatening ventricular arrhythmias when other treatments are ineffective or have not been tolerated.”

Pacerone Black Box Warnings

The Pacerone label includes Black Box warnings regarding a risk of sudden death, as well a number of potentially fatal toxicities. The most serious of these is pulmonary toxicity (hypersensitivity pneumonitis or interstitial/alveolar pneumonitis), which proves fatal about 10% of the time. The boxed warning also includes information about liver injuries, including rare cases of overt liver disease resulting in death.  It also notes that exacerbation of arrhythmia has occurred in 2 to 5% of patients treated with amiodarone, and that  significant heart block or sinus bradycardia has been seen in 2 to 5%.

“Even in patients at high risk of arrhythmic death, in whom the toxicity of amiodarone is an acceptable risk, amiodarone poses major management problems that could be life-threatening in a population at risk of sudden death, so that every effort should be made to utilize alternative agents first.”

Potential Pacerone Side Effects

Side effects and complications potentially associated with Pacerone include:

  • Skin reactions
  • Toxic Epidermal Necrolysis (TEN)
  • Lung damage
  • Chronic pulmonary fibrosis
  • Blindness
  • Muscle disease, injury
  • Myopathy
  • Rhabdomyolysis
  • Liver damage
  • High blood pressure
  • Worsening cardiac arrhythmias
  • Sudden death

Pacerone and Zocor

In 2011, the U.S. Food & Drug Administration (FDA) warned that combining amiodarone, the active ingredient in Pacerone, with the statin Zocor (simvastatin) had been linked to serious muscle injury (myopathy). To avoid this risk, Zocor should not be administered in doses greater than 20 mg when it is being used in conjunction with Pacerone.

Untreated myopathy can lead to rhabdomyolysis, as well as kidney failure and death. Symptoms of rhabdomyolysis include:

  • Muscle pain, tenderness, cramping, swelling
  • Weakness in the muscles, arms, or legs
  • Decreased urine output
  • Urine that is dark or cola-colored
  • Increased levels of creatine kinase enzyme in the blood
  • Fatigue
  • Irregular heart rhythm
  • Confusion
  • Nausea, vomiting
  1. S. National Library of Medicine (2011) “AMIODARONE HYDROCHLORIDE – amiodarone hydrochloride tablet”
  2. FDA (2005) “Information for Healthcare Professionals: Amiodarone”
  3. FDA (2011) ) FDA Drug Safety Communication: Revised dose limitation for Zocor (simvastatin) when taken with amiodarone)
Last Modified: May 5, 2016

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