Reactions to Antibiotics

Antibiotics are among the most commonly prescribed medications in the US. An antibiotic side (adverse) effect is an unwanted reaction that occurs in addition to the desirable therapeutic action of the antibiotic. When used appropriately, antibiotics are relatively safe with very few side effects. However, like any drug, antibiotic side effects can occur and may interfere with the patient’s ability to tolerate and finish the course of medication.
Antibiotic reactions can range from mild allergic reactions to severe and debilitating adverse events. Antibiotic side effects are extremely variable from patient to patient and from antibiotic to antibiotic. However, there are some common side effects that may occur within antibiotic drug classes.
If a patient is experiencing a bothersome or serious antibiotic side effect, they should contact their health care provider. The outcomes may include staying on the same antibiotic and managing the side effect, adjusting the dose, or switching to a different antibiotic. Usually, antibiotic treatment should not be stopped without a health care provider’s approval. Stopping the antibiotic may allow the infection to worsen and may lead to antibiotic resistance. Even if the infection appears to have cleared up before all of the medication is gone, the full course of antibiotic treatment should always be completed unless told otherwise by a health care provider.
An antibiotic allergy or hypersensitivity reaction can happen with any drug, and allergies are one of the most common antibiotic side effects leading to emergency room admission.1 Health care providers should always be informed of any previous allergic reaction to any medication, including antibiotics. Mild allergic reactions may only result in a skin rash. More severe allergic reactions, called anaphylaxis, can lead to shortness of breath, wheezing, hives, and swelling of the face, lips or tongue. Anaphylaxis is a medical emergency that requires immediate medical attention.
Antibiotics are used to kill bacterial infections; they are not effective against viral infections, such as a cold or the flu, or against fungal infections, like ringworm or vaginal yeast infections. The most common antibiotic classes and drug members are listed in Table 1, along with the most commonly reported antibiotic side effects. This is not a complete list of all available antibiotics or side effects that may occur.
In a 2008 study, antibiotic side effects led to greater than 140,000 emergency department admissions per year in the United States. Roughly 50 percent of emergency visits were due to reactions to antibiotics in the penicillin class of drugs, and the other 50 percent were due to a wide variety of antibiotics used to treat many different types of infections. In this study, children less than one year of age were found to have the highest rate of antibiotic side effects. Allergic reactions accounted for the most common type of side effect. It was estimated that over 142,000 emergency department visits per year were due to antibiotic adverse events, and approximately four-fifths of these events were due to allergic reactions. Allergic reactions can typically only be prevented by avoiding the drug, although desensitization may be possible in certain circumstances for patients who have no other antibiotic options.