It’s one thing to know that taking steroids can cause many unpleasant side effects. It’s quite another to think that it could kill you. Now researchers have found that a simple preventive step can erase a deadly outcome.

People with autoimmune diseases, such as lupus or rheumatoid arthritis, can be more susceptible to infections because their immune systems don’t tend to work as they should. At the same time, autoimmune diseases often involve flare-ups of damaging inflammation. A high dose of a steroid—often prescribed by doctors in these situations—can provide relief by reducing inflammation…but here’s the catch. The steroids also further weaken the immune system, leaving autoimmune patients even more vulnerable to infection.

And one kind of infection is particularly opportunistic and nasty—the lung infection called pneumocystis pneumonia (PCP). It’s not caused by anything exotic. In fact, the culprit is a common fungus. The fungus is rarely a problem if you have a healthy immune system—your body clears it easily. But for someone whose immune system is already compromised, taking 30 or more milligrams of steroids a day for four weeks or more increases not only the risk of acquiring PCP but also the risk of dying from it.

The study: Researchers analyzed the records of 1,092 people with autoimmune diseases who were on just such a course of steroids. They followed the patients for a year from the day that treatment started…that’s the time span in which the infection tends to develop. In addition to the steroids, about one-quarter of the study subjects also took the antibiotic combination trimethoprim/sulfamethoxazole—you probably know this treatment by the brand names Septra and Bactrim. They started the antibiotic on the same day that they started the steroid and stopped when the daily steroid dose was tapered off.

This antibiotic has been used against PCP in other kinds of patients, such as organ transplant recipients and people with HIV, but it had never been rigorously tested for autoimmune diseases such as lupus or rheumatoid arthritis. The goal of the study was to learn whether it could prevent participants from getting pneumocystis pneumonia, how well it did this job and how safe it was.

The findings: Just one person developed the pneumonia among people given the antibiotics, and that person had had to discontinue the antibiotic because of side effects. In comparison, there were 29 cases of pneumonia among the participants who weren’t given the antibiotics (and 11 of them died).

The researchers concluded that the benefits of giving this specific antibiotic treatment, along with long-term, high-dose steroids, far outweigh any risks.

In the know: You should still be aware of the signs of PCP. Any time you’re on high-dose, long-term steroids, tell your doctor right away if you have…

  • High fever or chills
  • Cough or trouble breathing
  • Chest pain
  • Extreme tiredness

It’s important to note that low-dose steroids can have their own serious side effects. For more, read “Low-Dose Steroids for Rheumatoid Arthritis: The Risks Are High.”