Explore Medicine with Chula Pharmacy: The Significance of Drug Allergies

    One recurring query posed to pharmacists is, "Do you have any history of allergies to medications, food, or chemical substances?" This question may be met with reluctance by many, as it's a query asked not only by pharmacists but also by nurses and doctors during various stages of medical care. The reason for this repetition is to safeguard patients from receiving medications to which they might be allergic, as drug allergies can provoke severe and even fatal reactions.

    Understanding Drug Allergies and Their Implications

    A drug allergy signifies an overly sensitive response of the body's immune system to a substance ingested, leading to symptoms like rashes, itching, hives, swelling of the mouth and eyes, drops in blood pressure, dizziness, rapid heartbeat, and even bronchospasm. In severe cases where immediate intervention is unavailable, it may culminate in respiratory failure or, in the worst scenario, death. Severe allergic reactions to drugs can also result in dermatitis and damage to various internal organs, such as hepatitis.

    Typically, drug allergy symptoms manifest shortly after the drug is introduced into the body. However, in some cases, these reactions can develop weeks or even months after the initial exposure, making them more challenging to identify. This delayed onset of drug allergies can be especially concerning, as patients might continue taking the medication without realizing they are allergic, potentially leading to more severe reactions.

    Unlike some other allergies, predicting drug allergies in advance is challenging. A family history of allergies to certain substances, such as food, alcohol, dust, or pollen, doesn't necessarily mean that siblings or children of the same parents will be allergic to the same things. Allergies often become apparent only when individuals are exposed to or ingest the triggering substance.

    Managing allergies involves using antihistamines to alleviate symptoms and, in severe cases, steroid therapy in conjunction with symptomatic treatment, until the allergy symptoms improve.

    The crucial factor for anyone with allergies is awareness. If you have allergies, especially to medications or foods, it's imperative to remember the names of the substances and the associated symptoms of your allergic reactions. If a healthcare facility provides a drug allergy card, always carry it with you to ensure that, in case of emergencies where you cannot provide information to responders, they can avoid administering medications to which you are allergic.

    Advancements in pharmacogenetics have led to the development of tests to identify genetic markers associated with drug allergies, particularly for drugs that can trigger severe reactions. This testing helps determine if a patient possesses genetic characteristics or genes indicating a higher risk of drug allergies. While not applicable to all medications, it has proven vital in reducing the risk of drug allergies. For instance, for allopurinol, a critical medication used to treat gout, individuals can now be screened for the presence of the HLA-B*5801 gene. If detected, these individuals are over 300 times more likely to experience severe allergic reactions to allopurinol and should avoid using it, necessitating alternative gout treatment options.

    Beyond allopurinol, several other drugs can also be tested for genetic markers to predict drug allergies. For example, anticonvulsant drug carbamazepine and specific HIV antiretroviral medications warrant genetic testing for those at risk.

    In conclusion, severe allergic reactions to drugs can be life-threatening and may occur suddenly or even after prolonged usage. Individuals with a history of drug allergies must keep the drug names and allergic symptoms in mind, and if available, always carry a drug allergy card to prevent accidental exposure to allergenic drugs.

Assoc. Prof. Dr. Nattada Areepiam and Asst. Prof. Dr. Bodin Tiwasuwan

Faculty of Pharmacy Chulalongkorn University