Vanderbilt University Medical Center Professor of Medicine, Dr. Elizabeth J. Phillips, talks about penicillin allergy.
Interview conducted by Ivanhoe Broadcast News in 2023.
Back in the ages, doctors use penicillin all the time. Do you think that’s why some patients automatically claimed an allergy because they didn’t know of any other drugs?
PHILLIPS: I think that what’s key is that penicillin as a drug has evolved considerably over time. So the early formulations of penicillin were injectables. They were basically different drugs and we use today in the way they were manufactured and the processing of them. So I think some of the early reactions patients had with these injectable forms of penicillin that were given in the muscles like intramuscularly have no relationship to the reactions that are described today. And that’s one of the reasons why I think we don’t see as much penicillin allergy today is that the formulations we’re using today are so different and are more highly purified.
How can patients be sure they won’t get anaphylaxis?
PHILLIPS: So many patients will have concerns that they will have a serious reaction to penicillin. And the stems again to the fact that very often, these labels go back to childhood. The patients have been told by a parent that they’re allergic to penicillin. So they’ve been told by someone that they trust never to take it again. And so the risk of true anaphylaxis associated with penicillin is less than one in 10,000. So the risk is really low. If a patient has a high risk history and we see a lot of patients like in this clinic that have a high risk history then we can do specialized testing. And under that, with the specialized testing where we can do skin testing followed by a challenge in the clinic. If the testing is negative, the risk is very low if any reaction happening. So if there is a risk associated with penicillin allergy, then we recommend patients actually get that assessed by in a specialty clinic where they can actually do specialized testing where the risk is really low. However the chance of being delabeled even with a remote history of a severe reaction is very high.
How important is penicillin?
PHILLIPS: Penicillin was one of the first antibiotics developed. It wasn’t the only antibiotic developed. We had sulfa antibiotics in the 1930s, but penicillin is really the first line antibiotic for so many different types of common infections like skin infections or pneumonia. And drugs in the penicillin family and its relatives are used for almost every type of infection you can imagine. And because now there’s so many derivatives of penicillin, even more complex infections like those that occur in the hospital, respond to drugs in the penicillin family. Importantly, if someone has a label of penicillin allergy, because there are now families of drugs that are derived from penicillins and we call one class cephalosporins, patients labeled as penicillin allergic will often unnecessarily avoid these related drugs. And so having a penicillin allergy label is a real liability because it leads to avoidance sometimes of a whole family of drugs which are the first line treatment for almost every type of infection.
What offshoots of penicillin cannot be used in an allergy situation? So are there any allergies situations that would affect it?
PHILLIPS: So is there any context where we wouldn’t consider using penicillin? So we have, good information about how to use risk of history to manage penicillin allergy. And low-risk patients are those in particular that have had a remote reaction more than 10 years ago. In particular, those that did not require any treatment for their reaction and basically it went away spontaneously. They didn’t need to be seen by a doctor or go to hospital. Those that just had a mild rash or a skin rash that came and went. All of these are really low risk situations that were likely not an allergy to being with. Where we do get concerned is if patients have had an immediate reaction where they’ve had in involvement of multiple systems. So not just a rash, but they have breathing difficulty or their blood pressure drops so they have to go to hospital and be treated with epinephrine or an epipen, then we get concerned about that history and those patients should avoid penicillin until they can be appropriately tested. And then less common than that there are some severe reactions that tend to be more delayed. They’re less commonly associated with penicillin but can be associated with other drugs. And these are what we call severe delayed reactions. They often affect the skin or an organ, and they can lead to severe skin reactions like Stevens-Johnson syndrome is one example, or they can affect an organ like the liver or kidney. And if a patient has had that type of reaction that has been associated with a penicillin then we don’t recommend they get penicillin in the future.
Are there any other important facts or research or anything that you want to share?
PHILLIPS: So I think one of the challenges in the United States and globally. And to use the example of the United States. Because we know that around 10% of the population is actually labeled as being penicillin allergic. This means that there’s 30 million people in the United States right now that are walking around with that type of label. And we have good research. Now, we’re just about to publish a randomized study that looks at going straight to giving an oral dose of a penicillin to delabel of penicillin allergy versus using skin testing followed by that “oral challenge”. And the gold standard of actually removing a penicillin allergy label always has to be follow skin testing performed in an Allergist’s office by that challenge step. So that’s the necessary step. But skin testing at this point in time can only be performed in a specialized setting. So that means basically an allergist’s office. And so that means that the number of doctors and health care providers that could actually remove a label of penicillin allergy at this point in time, if we have to do skin testing, is really going to be limited and there won’t be the capacity to actually address the burden of penicillin allergy labels in the population. However, with this new information that we have from this study that was performed in adults, it suggests that now this could be potentially broadened to the inpatient setting where a patient comes in and is hospitalized and can have their penicillin allergy removed through an oral challenge in hospital. Or maybe it could be done by the patient’s primary care provider just like a routine preventive health visit. We do this routinely for vaccination or any other preventive health measures. So it just means that we can really start addressing the problem without the need for specialized testing. Specialized testing, there’s always going to be a role for that in patients that have these more severe reactions as I outlined.
END OF INTERVIEW
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
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