When we talk about antibiotic allergy, the most common is penicillin and its derivatives. Penicillin is prescribed to treat various bacterial infections.
Teste de allergyFoto: Monika Wisniewska | Dreamstime.com
Common signs and symptoms of penicillin allergy include hives, rashes, and itching. Severe reactions include anaphylactic shock, which is life-threatening and affects multiple major organs.
Research has shown that penicillin allergies may be overreported—a problem that can lead to the use of less appropriate and more expensive antibiotic treatments. Therefore, an accurate diagnosis is necessary when penicillin allergy is suspected.
“Antibiotics are among the most common drugs involved in allergic reactions, especially those from the beta-lactam class, of which penicillin is a part,” explains Dr. Rareș Simu, specialist in clinical immunology and allergology.
Why do we develop penicillin allergy?
Penicillin allergy occurs when the immune system becomes hypersensitive to the drug—mistakenly reacting to the drug as a harmful substance, such as a viral or bacterial infection.
Before the immune system develops sensitivity to penicillin, you must have been exposed to the drug at least once. After exposure, the immune system may develop antibodies against the antibiotic. And on the next administration, these specific antibodies direct the immune system’s attacks on the drug. The chemicals released by this activity cause the signs and symptoms associated with an allergic reaction.
How antibiotic allergy manifests itself and how long it lasts
Signs and symptoms of penicillin allergy often appear within an hour of taking the drug. Rarely, reactions may occur hours, days or weeks later.
Signs and symptoms of penicillin allergy may include:
Anaphylactic shock
Anaphylaxis is a rare, life-threatening allergic reaction. Signs and symptoms of anaphylaxis include:
constriction of the airways and throat, causing difficulty breathing; nausea or abdominal cramps; vomiting or diarrhea; dizziness; weak, rapid pulse; lowering blood pressure; convulsions; loss of consciousness.
Delayed allergic reactions to penicillin
Uncommon allergic reactions to penicillin occur days or weeks after exposure to the drug and may persist for some time after you stop taking it. These include:
serum sickness, which can cause fever, joint pain, rashes, swelling and nausea; drug-induced anemia, a reduction in red blood cells, which can cause fatigue, irregular heartbeat, shortness of breath, and other signs and symptoms; drug reaction with eosinophilia and systemic symptoms (DRESS) resulting in skin rash, high white blood cell count, generalized inflammation, enlarged lymph nodes and recurrence of infection hepatitis latent; Stevens-Johnson syndrome or toxic epidermal necrolysis, which involves severe blistering and peeling of the skin; inflammation of the kidneys (nephritis), which may cause fever, blood in the urine, generalized inflammation, confusion, and other signs and symptoms.
Other adverse effects, other than allergy
It is possible to have side effects of penicillin – as with other drugs – that are not an allergic reaction to the drug. Depending on the type of penicillin, common side effects may include: nausea or mild diarrhea, headache, or vaginal itching.
“In all cases where an allergy to a drug occurs, the administration of any drugs in the same class should be avoided. The incriminated drug must be replaced with a drug with a similar effect, but which has a different chemical structure and which acts through other mechanisms”, says Dr. Rareș Simu.
Penicillin derivatives that can cause allergic reactions
Penicillin belongs to a class of antibacterial drugs called beta-lactam antibiotics. Although the mechanisms of drugs vary, they generally fight infections by attacking bacterial cell walls. In addition to penicillin, other beta-lactams more commonly associated with allergic reactions are a group of drugs called cephalosporins.
If you have had an allergic reaction to one type of penicillin, you may also be allergic to other types of penicillin or some cephalosporins.
Penicillin derivatives include:
amoxicillin, ampicillin, dicloxacillin, nafcillin, oxacillin, penicillin G, penicillin V, piperacillin, ticarcillin.
cephalosporins include:
cefaclor, cefadroxil, cefazolin, cefdinir, cefepime (Maxipin), cefotetan, cefprozil, cefuroxime, cephalexin (Keflex).
Risk factors
Anyone can develop an allergic reaction to penicillin, however there are some predisposing factors:
a history of allergies to other substances such as food allergy sthey have hay fever; allergic reaction to another drug; a family history of drug allergy; increased exposure to penicillin, due to high doses, repetitive use, or prolonged use; certain diseases commonly associated with allergic reactions to drugs, such as HIV infection or Epstein-Barr virus.
Diagnosis of antibiotic allergy
Thorough consultation and appropriate diagnostic tests are essential for a correct diagnosis. A misdiagnosed penicillin allergy may lead to the use of less appropriate or more expensive antibiotics.
Skin tests
During a skin test, the allergist applies a small amount of medicine to the skin with a needle. A positive reaction to the test will cause a red, itchy bump.
A positive result indicates a high probability of penicillin allergy. A negative test result usually means that you are not at high risk for penicillin allergy. But a negative result is more difficult to interpret because some types of drug reactions cannot be detected with skin tests.
Challenge test
If the diagnosis of penicillin allergy is uncertain, a challenge test may be recommended. This procedure is done in hospital and involves the administration of up to five doses of penicillin, starting with a low dose and increasing to the desired dose. If you reach the therapeutic dose without any reaction, then the doctor will conclude that you are not allergic to that type of penicillin. You will be able to take the medicine as prescribed.
If you are allergic to one type of penicillin, your doctor may recommend a challenge test with another type of penicillin or cephalosporin that is less likely – because of known chemical properties – to cause an allergic reaction. This way it can identify an antibiotic that can be used safely.
Amoxicillin allergy and penicillin allergy, substitute
“With penicillin or amoxicillin, for example, which are broad-spectrum antibiotics, if the patient with a bacterial infection is allergic to them, another broad-spectrum antibiotic that is not in the same class is recommended. In general, it is preferable to administer drugs, namely antibiotics, which the patient has previously administered and which were well tolerated”, recommends Dr. Rareș Simu.
If there are no other appropriate antibiotic treatment options available, your doctor may recommend drug desensitisation treatment.
It involves taking a very small dose and then progressively larger doses every 15 to 30 minutes over several hours or days. If you reach the desired dose without any reaction, then you will continue the treatment.
It is important to take the medication as directed to maintain tolerance to it throughout the course of treatment. However, desensitization does not last over time, so you need to repeat the procedure if you need antibiotic treatment afterwards. Unfortunately, desensitization is not always successful and there is a risk of serious reactions.
Antibiotic allergy in children
According to data published in Journal of Pediatric Infectious Diseases Societyantibiotic side effects accounted for more than 70,000 pediatric emergency room visits in the United States between 2011 and 2015.
Most of the visits to the doctor (over 86% of cases) were caused by allergic reactions, such as eczema, pruritus and edema. The risk of going to the emergency room varied by age and the type of antibiotic used, but the most common reactions occurred in children younger than two.
Amoxicillin was the antibiotic most often involved in adverse events in children under 9 years of age, while sulfamethoxazole and trimethoprim (which appear in products such as Biseptrim, Sumetrolim, Tagremin) caused the most frequent allergic reactions in children between 9 and 14 years.
“It is recommended to avoid the abuse of drugs, especially antibiotics and especially in children, without having a definite medical indication,” says Dr. Rareș Simu.
2023-07-17 17:14:00
#discover #antibiotic #allergy
