There are several classes of adverse drug reactions, and one part corresponds to the so-called hypersensitivity or allergic reactions.
According to the WHO, an adverse reaction to a drug is any harmful and unintended effect produced by a drug that occurs with the doses used in humans for the prevention, diagnosis or treatment of diseases.. They are the most frequent adverse reactions and do not require any analysis by the allergist , such as epigastralgias caused by anti-inflammatories and acetylsalicylic acid, adverse effects of corticosteroids that can appear with its continuous use and many others.
Symptoms of allergy to medicines. The patient is frequently consulted by the physician after administering intramuscular penicillin or by dizziness that may occur after a dental intervention. In most of these cases, the cause is a drop in pressure from the same prick pain or apprehension on the part of the patient and have nothing to do with allergic reactions.
The true allergic reactions can present with different symptomatology:
You can talk about immediate allergic reactions. These involve an allergic mechanism involving IgM inmonuglobulin. They usually occur within the first hour after administration of the drug. They are not hereditary, so it is not necessary to study allergy to a patient with a family member allergic to the same drug. It can give symptoms of diverse severity as skin problems (urticaria itching, angioedema), respiratory (drowning), cardiocirculatory (hypotension, tachycardia) and digestive. Allergy with involvement of various organs is called anaphylaxis. In some cases it could be very serious and even involve the death of the patient.
Delayed hypersensitivity reactions may also occur. These may also include various types of reactions, some of them serious with involvement of the patient's skin.
Diagnosis of drug allergy
The diagnosis or analysis of drug allergy depends on the particular drug and the type of reaction. Some blood tests may be helpful in some medications but this is generally only the first step in the study of allergy. Skin tests are performed with other drugs, and in many cases a hospital-controlled exposure test with the same or alternative drugs is required as the final test.
Not always when there is a suspicion of drug allergy will require specific analysis. In those cases where the reaction has been produced by a non-essential drug, easily replaceable by another and that the patient is not going to need again no study will be required.
In contrast, other drugs that may be essential, such as insulin in a diabetic patient, should always be studied if there is suspicion of allergy. It may also be advisable to study anti-inflammatory drugs or in some antibiotics such as penicillin since a patient may need them at some point.
Any medication may be responsible for an allergic reaction, although the most frequently are -lactam antibiotics (including penicillin), anti-inflammatories and acetylsalicylic acid. Although the excipients that accompany the medicines could be in exceptional cases the cause of an allergic reaction, this is not the norm so if there is a suspicion of allergy of a medication all medicines should be avoided containing the same active ingredient although different pharmaceutical brands.
It may be the case that the drug is a factor that triggers a food allergy, so that even if there is suspicion of drug allergy will also require a food allergy study.