The U.S. Food and Drug Administration (FDA) wants consumers and physicians to know about the risk of developing severe skin reactions associated with the antiepileptic drug Onfi.

Onfi (clobazam) is used in conjunction with other medications to treat a specific and severe form of epilepsy called Lennox-Gastaut Syndrome. It is produced by the Lundbeck company of Denmark.

Onfi had been sold outside the United States for decades when the FDA approved it for U.S. sale in October 2011. Soon thereafter, the U.S. market accounted for the lion’s share of Onfi sales.

In December 2013 the FDA released a Drug Safety Communication warning of the possibility of developing two severe skin conditions, Stevens Johnson Syndrome and toxic epidermal necrolysis, as side effects of Onfi treatment.

Stevens Johnson Syndrome, or SJS, is known chiefly for its effects on the skin. It causes symptoms similar to those of severe burns. The condition initially presents symptoms similar to the flu, such as body aches, fever and headache.

Within a few days, blisters begin to appear on the skin. These blisters can coalesce into large areas of skin that slough off of the body, exposing the patient to infection and the possibility of sepsis. The patient may also lose fingernails, toenails, or eyebrows.

SJS may also cause eye symptoms such as keratoconjunctivitis, and the epithelial tissue inside the lungs may slough, leading to respiratory complications such as pneumonia or pulmonary edema. The most serious cases of SJS can be fatal.

SJS that has advanced to cover over 30 percent of the body’s surface area is usually referred to as toxic epidermal necrolysis, or TEN. Both SJS and TEN are rare.

However, in the majority of cases, these conditions occur as side effects of some sort of medication. The array of different types of medications that cause them is varied. Antiepileptics like Onfi are among the more common causes.

Treatment of SJS often requires weeks of hospitalization and monitoring. SJS usually begins to resolve after the patient stops taking the offending medication, and the FDA recommends discontinuing Onfi treatment at the first sign of rash. However, sudden cessation of Onfi treatment creates a new risk of serious withdrawal symptoms, such as unstoppable seizures, hallucinations, shaking, nervousness, and stomach or muscle cramps.

Onfi Side Effects

The FDA’s December 2013 communication was based on analysis of 20 cases of SJS and TEN that occurred simultaneous with administration of anti-epileptic drugs including Onfi. In many of those cases, the FDA found evidence that Onfi was the likely cause of the skin reaction.

All patients in these cases required hospitalization. One case resulted in blindness, and one other resulted in death. The agency approved a revision of the labeling for Onfi that would more adequately describe the risk of Onfi side effects.

The impact of Onfi side effects can be devastating. Recovery time can require weeks away from work and extraordinarily burdensome medical expenses. An Onfi lawsuit may be an avenue to compensation for patients suffering from Onfi-related SJS or TEN.