Optic Neuritis: Overview
As the name suggests, optic neuritis is an inflammatory condition affecting the optic nerve, also known as cranial nerve II or simply CN2. It consists of a pair of nerves, running from the back of the eyeball to the mid-brain; its function is to transmit visual data from the retina.
Optic neuritis may lead to vision loss, ranging from slight to total blindness. Color vision may be affected. Vision may return to normal within 8 to 12 weeks, but recovery may not be complete. The condition is recurring in some patients.
Optic Neuritis: Causes
Optic neuritis is considered a generalized symptom. The condition may result from:
- multiple sclerosis (most common)
- infections (including HIV)
- cancer
- toxins such as lead, methyl alcohol or arsenic
- some antibiotics or quinine
Optic Neuritis as a Side Effect of Amiodarone
The condition has been linked to the drug amiodarone, which is regarded by cardiologists to be a treatment of last resort.ย Nine out of 10 patients who take amiodarone for an extended period at higher doses (400 mg per day or more) wind up with a condition known as cornea verticillata, or whorl keratopathy. These are micro-deposits that build up on the cornea as a result of taking amiodarone.ย In most cases, patients with cornea verticillata do not experience symptoms; however, up to 2 percent of those taking amiodarone wind up suffering optic neuritis.
Why Amiodarone is Prescribed
The prescription drug amiodarone is generally used to treat various forms of irregular heartbeat (arrhythmia). Development of the drug dates back to the mid-1940s, when Russian physiologist Gleb von Anrep was working in North Africa and noted that the khella plant (also known as Bishop’s Weed, a member of the carrot family) had therapeutic properties. Amiodarone is based on a khella extract, known as khellin.
Amiodarone is indicated for atrial fibrillation (a-fib) and tachycardia only as a treatment of last resort after the patient has failed to respond to other medications or treatments. Optic neuritis is one of several serious side effects associated with amiodarone.
Amiodarone: Safety Concerns
Amiodarone was finally introduced in 1961. It was commonly prescribed in Europe and Canada for the treatment of angina pectoris. it was not approved for sale in the U.S. until 1985 because of concerns over its potentially harmful effects on the respiratory system. Approval came as a result of pressure by European drugmakers, who threatened to cut off the supply to U.S. doctors if it was not approved.
In addition to optic neuritis, side effects of Amiodarone may include:
- Pulmonary (lung) damage
- Liver failure
- Neuropathy (nerve damage)
- Heart failure
- Kidney failure
Legal Issues
Current lawsuits allege that at least one manufacturer of amiodarone has marketed the product as a first-line treatment, whereas under the terms of its FDA approval, it should be prescribed only when all other treatments have failed.
According to plaintiffs, the drug company in question, Wyeth, was so successful in marketing its own version of amiodarone (Cordarone) that cardiologists and primary care physicians were convinced to prescribe it to their patients as a first-line treatment when they may not have needed it at all.
As a result, these patients say they suffered needlessly from optic neuritis and other complications. Other major pharmaceutical companies have been accused of illegal off-label marketing of amiodarone.