Pathophysiology: A drug allergy is the abnormal reaction of the immune system to a medication. Any medication — over-the-counter, prescription or herbal — is capable of inducing a drug allergy. However, a drug allergy is more likely with certain medications. The most common signs and symptoms of drug allergy are hives, rash or fever. A drug allergy may cause serious reactions, including anaphylaxis, a life-threatening condition that affects multiple body systems. A drug allergy is not the same as drug side effects, the known possible reactions that are listed on a drug label. A drug allergy is also distinct from drug toxicity caused by an overdose of medication. A drug allergy occurs when your immune system mistakenly identifies a drug as a harmful substance. In most cases, a drug allergy develops when your immune system has become sensitive to the drug. Statistical report: ADRs account for 3% to 6% of all hospital admissions and occur in 10% to 15% of hospitalized patients. Drug allergy is relatively uncommon, accounting for less than 10% of all ADRs. Drug allergy, occurs in 1% to 2% of all admissions and 3% to 5% of hospitalized patients, respectively but the true incidence of drug allergy in the community, and among children and adults, is unknown.
Many children are misdiagnosed as being “allergic” to various medications, particularly antibiotics and end up carrying this label into adulthood. These patients are frequently treated with alternate medication that may be more toxic, less effective and more expensive – this in turn may result in increased morbidity, mortality and cost. Treatment: The following interventions may be used to treat an allergic reaction to a drug: • Withdrawal of the drug. If your doctor determines that you have a drug allergy — or likely allergy — discontinuing the drug is the first step in treatment. In many cases, this may be the only intervention necessary. • Antihistamines. Your doctor may prescribe an antihistamine or recommend an over-the-counter antihistamine such as diphenhydramine (Benadryl) that can block immune system chemicals activated during an allergic reaction. • Corticosteroids. Either oral or injected corticosteroids may be used to treat inflammation associated with more-serious reactions. •
Treatment of anaphylaxis. Anaphylaxis requires an immediate epinephrine injection as well as hospital care to maintain blood pressure and support breathing. Research works: Many novel drugs have been introduced, generating new patterns of drug hypersensitivity. There are also novel clinical and biologic techniques that have enabled us to understand the mechanisms and diagnosis of reactions to old used drugs. Immuno-Cap, ELISA, enzyme-linked immunospot assays, and T-cell proliferation tests allowing novel approaches to assess drug allergy.