Patients taking a routine course of antibiotics are not likely expecting to develop a serious skin side effect.

But when Zithromax treatment leads to Stevens Johnson syndrome, the effects can be severe, and sometimes permanent.

Zithromax (azithromycin) is an antibiotic that has been on the market since 1991, when it was first approved by the FDA. It’s particularly popular, sold as a five-day course under the brand name Z-Pak. It can also be administered in a single large dose, marketed as Zmax.

As its FDA-approved label states, Zithromax treatment can, in rare cases, lead to development of Stevens Johnson syndrome or its related, and more severe, condition toxic epidermal necrolysis.

Stevens Johnson syndrome is a disorder of the skin and mucous membranes. It is rare, but when it does occur the effects are severe, painful, and potentially life-threatening. And more than half of SJS cases, and up to 90 percent of cases of TEN, can be attributed to drugs like Zithromax.

The first signs of SJS tend to resemble flu symptoms, such as cough, fatigue, body aches, and fever. Patients may also experience soreness in the throat or mouth or a burning sensation in the eyes.

Soon after that, the skin begins to show areas of painful rash and discoloration over the trunk and face, sometimes spreading to the rest of the body. The areas of rash enlarge and form blisters in their centers.

The skin over the blisters loosens and tends to slough off. In SJS specifically, the affected areas of skin is typically less than 10 percent of the body’s surface. Where the affected area grows to 30 percent or more, the condition is referred to as toxic epidermal necrolysis.

Symptoms similar to those on the skin may also attack the mucous membranes. This can affect areas of the eyes, genitals, mouth, throat, or elsewhere in the digestive tract.

Treatment for a condition as overwhelming as SJS requires hospitalization, usually in a burn unit for more advanced cases. First, the underlying cause must be eliminated. When the condition is caused by a drug, the patient must stop taking that drug as soon as possible.

After that, treatment focuses on managing symptoms and avoiding complications. The loss of the top layer of skin puts the patient at risk for infection, so blisters and areas of lost skin will require wound dressing. The loss of skin also results in significant loss of fluids and salts, which may need to be replaced intravenously.

The patient may benefit from pain medication, antihistamines to reduce irritation, or antibiotics to control infection. Recovery from SJS can take weeks or months, and patients may still be left with permanent residuals.

The harm brought on by SJS or TEN can be catastrophic, and it’s not just limited to pain and suffering. Patients undergoing a long hospitalization for SJS will rack up considerable medical bills while at the same time being unable to earn income.