The U.S. Food and Drug Administration (FDA) issued a Drug Safety Communication advising the public that the anti-seizure drug Onfi (clobazam) may be linked to life-threatening complications.

Onfi is an important drug for controlling several seizure disorders, including many forms of epilepsy. In some countries the drug is also approved for treating acute and chronic anxiety.

This may lead to off-label use of the drug for this purpose in the United States, which is permissible under FDA regulations. However, the Drug Safety Communication issued in 2013 indicates that the FDA has some serious concerns about Onfi side effects.

According to the Drug Safety Communication, the FDA was mandating changes to the drug information packaged with Onfi due to new concerns that the drug could cause Stevens Johnson Syndrome and a closely related disorder called toxic epidermal necrolysis.

Stevens Johnson Syndrome, or SJS, is an autoimmune disease in which the immune system malfunctions and attacks the patient’s own skin. SJS symptoms include generalized, flu-like symptoms like muscle aches, chills, and fever. However, this escalates to a painful rash with blisters, sores and ulcers. The damage can spread to the inside of the nose and mouth, and even the eyes and surfaces of internal organs. The damage from SJS can be fatal, and survivors face debilitating and disabling complications like widespread scarring, blindness, and impaired organ function. Many questions remain about Stevens Johnson Syndrome, but the vast majority of cases appear to be triggered by drugs, including Onfi.

The most extreme cases of SJS escalate to a related disorder called toxic epidermal necrolysis. TEN symptoms are more severe than those of SJS, though there is some overlap. With TEN, patches of the patient’s skin die and slough off, leaving wounds very similar to thermal burns.

This damage is so similar to burns that hospitals often treat TEN patients in their burn wards. TEN patients even face many of the same complications as burn patients, such as secondary infection, dehydration, and hypothermia due to a loss of skin covering. As many as 40 percent of patients who contract TEN may die from the reaction, though the mortality rate varies by severity. Like SJS, TEN is nearly-always triggered by reactions to drugs like Onfi.

SJS lawsuits have been filed by patients who developed SJS or TEN after taking drugs like Onfi. These SJS lawsuits typically allege that drug makers did not do enough to protect people from possible Onfi complications like SJS and TEN.

Onfi lawsuits may further allege that not only were drug makers aware of these risks, but that they aggressively marketed the drugs in spite of the risk, endangering the public. SJS lawsuits typically seek to recoup the cost of medical care, lost wages, legal fees, lost income potential, and other costs linked to SJS and TEN allegedly triggered by Onfi or other drugs.