Zithromax has earned a reputation as a quick remedy for some more common types of bacterial infections.

However, in rare cases, that convenience comes at the cost of severe Zithromax skin reactions that can leave permanent damage or may even be fatal.

Zithromax is Pfizer Inc.’s brand name for the antibiotic azithromycin. It’s approved by the FDA to treat bacterial infections of the skin, respiratory system, and genitourinary system, as well as middle ear infections in children. Zithromax is one of a class of antibiotics called macrolides, which fight bacteria by preventing them from making the proteins they need to grow.

Because azithromycin remains active in the body for a relatively long time, it can be administered in shorter courses than can other antibiotics. The same ingredient in Zithromax is also formulated as single-dose Zmax and in three- and five-day course packs know as Z-Paks.

These short, easy-to-take courses have made Zithromax popular. Sales in the U.S. in 2012 reached $435 million, despite competition from generic versions.

Despite Zithromax’s popularity, there have been reports of serious skin reactions occurring simultaneous with Zithromax treatment. These reactions can include the potentially fatal conditions Stevens Johnson Syndrome and toxic epidermal necrolysis.

Both conditions tend to begin with non-skin symptoms including fever, headache and cough – symptoms that can resemble those of the flu. After that, the skin breaks out in a discolored rash. Blisters form near the center of the areas of rash. As the rash and blisters progress, they may coalesce and form large areas of skin that peel away.

The area of skin affected is the main difference between SJS and TEN. In SJS, generally less than 10 percent of the body’s surface is affected, and TEN affects 30 percent or more. There is some overlap between the two conditions. Medical science now considers them two extremes of the same skin reaction.

Other parts of the body may also be affected. The eyes may develop conjunctivitis, purulence, or corneal damage. Hair and nails may fall out. Mucous membranes in the digestive system and genitals may be affected, causing diarrhea, difficulty breathing, and pain on swallowing.

Because of the relatively high risk of death, treatment of SJS and TEN should begin early – though timely diagnosis may be confounded by the tendency for early SJS and TEN symptoms to mimic the flu. In most cases, the condition is caused by a drug like Zithromax, so the first step in treatment is to discontinue the causative drug.

Ttreatment itself requires hospitalization with management of symptoms. Typically the patient will need substantial fluid and electrolyte replacement, wound care, and prevention of infection. Severe cases may require treatment in a burn unit.

Even after the condition has resolved, 50 percent of patients continue to have long-term issues. The skin may have permanent bumps, discoloration, or scars.

The effects of SJS or TEN on the patient’s life can be devastating. In addition to the pain and suffering, weeks of hospitalization will generate burdensome medical bills while preventing the patient from earning income.