Each week we will aim to bring out a concise email that provides 4-5 key pieces of information addressing a specific issue in clinical therapeutics.
This week: Antibiotic Allergies
Andrew Wood, Regional Pharmacist Manager, Ward MM
Sensitivity to antibiotics, like other medicines, can present in different ways and via different physiological mechanisms.
- True allergies involve an immunologically-mediated reaction, where the body essentially launches a defence against something identified as foreign to it. This could be immediate and severe, in the form of anaphylaxis, or delayed and mild, such as a late-onset rash. Swelling of the mouth or lips is another possible presentation.
- Many adverse effects, e.g. GI upset, are inaccurately identified as ‘allergies’. It’s important to document the difference.
- If a true immunological allergy occurs, any subsequent use is likely to result in the same or more severe reaction, and the medicine should now be regarded as contraindicated for that resident.
- While it is usually not advisable to re-administer a medication known to cause an adverse effect, a non-immunological reaction does not definitavely contraindicate future use, which may be necessary if that is the best or only treatment option available.
- Allergy to penicillin is the most widely described antibiotic allergy. Cephalosporins and sulfonamides are also commonly implicated. Much of this may be a function of how often these agents are used, as well as potentially being a function of misidentified adverse effects.
- There is some cross-sensitivity between penicillins and cephalosporins; perhaps 5-10% of those allergic to one class will be sensitive to the other as well. Where there has been an anaphylactic reaction to one, both classes are usually best avoided.
- Sulfonamides are chemically classified as part of the broader ‘Sulfa’ group of medicines, which also includes some diabetes medicines and various others. Note that this doesn’t mean someone is allergic to the element ‘sulfur’ or sulphates – a common misconception.
Please consider these issues when preparing or interpreting RMMR reports or education sessions. Contributions of content or suggested topics are welcome and should be sent directly to firstname.lastname@example.org.