Antibiotic Can Cause Reaction in Penicillin-Sensitive Patients

Even though the antibiotic cephalosporin can set off allergic reactions in penicillin-sensitive patients, one out of ten non-allergist physicians said that they would prescribe it even for patients known to have had severe reactions to penicillin, according to a survey conducted by Medical College of Wisconsin researchers.

The survey results show a need for more continuing education among doctors in the area of penicillin allergy, said study co-author Michael C. Zacharisen, MD, Associate Professor of Pediatrics and Medicine.

"I worked with Dr. Thomas Puchner, Jr., on the study while he was at the Medical College on a fellowship to train in allergy," said Dr. Zacharisen. "Prior to the fellowship he was a practicing internist for ten years, and what he was hearing about penicillin allergy and cephalosporin from the experts in lectures was not what he had seen in private practice. So the whole goal of the survey was to find out what people are really doing in practice. Are they following guidelines and expert opinion, or are they simply doing what they’ve always done?"

Students, residents, general internists and allergists were among the 378 physicians surveyed. The researchers learned that all of the allergists said that they would not prescribe cephalosporin to someone who had once had a severe reaction to penicillin, but 11% of non-allergist doctors said that they would.

For patients who had had milder reactions to penicillin, such as a rash, more than half of the pediatricians and more than one third of the allergists surveyed said they would prescribe cephalosporin. And one out of three internists and pediatricians were unaware that standardized skin tests for penicillin allergy are readily available.

About the Allergies and Reactions
Penicillin was discovered in 1928, and the antibiotic Cephalosporin C was isolated in 1953. Penicillin-allergic patients might also be allergic to cephalosporin. The study noted, however, that while physicians routinely avoid prescribing penicillin to patients with penicillin allergy, the approach to prescribing cephalosporin is less clear.

"Any antibiotic - in fact almost any medication - has the potential to cause an allergic reaction," said Dr. Zacharisen. "Usually it’s antibiotics, because they are frequently given, and usually it’s penicillin or its derivatives because they’re the most frequent used antibiotics."

"There are different types of cephalosporins," Dr. Zacharisen explains. "There have been three generations, and as the newer ones come out they have different aspects about them that are good. It appears that penicillin is more closely linked or similar to the first generation of cephalosporin. So if you have a reaction to penicillin you’re more likely to have a reaction to the first generation of cephalosporin, less so to the second, and even less so to the third."

"The most common reactions are skin reactions- rash, hives and swelling. Reactions can range from mild skin reactions to severe skin reactions to anaphylactic shock," said Dr. Zacharisen. Anaphylactic shock is often severe and sometimes fatal, with characteristics that include respiratory symptoms, fainting, itching, and raised patches of skin or mucous membrane.

"There are many people who have had allergic reactions as infants, children or young adults," said Dr. Zacharisen, "and as time goes along that risk decreases. But you can have an allergic reaction at any point in your life, so your first penicillin or cephalosporin reaction may not be until you’re an adult or even an elderly person. We don’t know exactly why that is."

Simple Skin Test Aids Detection
Dr. Zacharisen said that there are about 50 deaths from penicillin anaphylaxis in the US each year, while between 4% and 5% of all persons may be penicillin sensitive and exhibit the milder symptoms. "Here at the Medical College we generally see those patients with the more severe reactions who come to us from primary care physicians," he said, "hence the survey to find out what’s really going on in practice."

"The symptoms of penicillin allergy can be similar to those of any other allergy, such as allergies to foods or other drugs. There are no specifically distinguishable symptoms for these antibiotic allergies. The most important thing is the temporal relationship. You take the medication and then the symptoms occur. When we’re evaluating patients for a medication allergy, they may be on six medications and the question is, which one is it?"

"Unfortunately, we don’t have any good allergy skin tests for any antibiotic other than penicillin," said Dr. Zacharisen. "If people want to know if they’re allergic to cephalosporin, there’s not a good, accurate way to tell that." The knowledge that a patient is sensitive to penicillin is a predictor of sensitivity to cephalosporin, though, which makes the standardized skin test for penicillin allergy a useful tool. One of the outcomes from the survey that Dr. Zacharisen hopes for is that more pediatricians and internists will be made aware of the availability of the skin test.

"Generalists have to take care of all groups of patients and all diseases, but when it comes to drug allergies there have been some recent advances. It’s difficult for doctors to keep up with everything in the field, especially knowing what skin tests are available. For a period of time even the penicillin skin test was not available on the market but then it came back. I think the biggest thing is education. What are we teaching students and residents? And what are the allergy education needs of community physicians?"

Dan Ullrich
HealthLink Contributing Writer

For more information on this topic, see the HealthLink article Sneezing, Wheezing, Coughing, Swelling... Is it an Allergy?

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.