Drug allergy

The drug allergy is a very common reason for consultation in our midst.

Medications are administered in order to exert their beneficial effects on the people who receive them, according to the different types of diseases, however, in addition to these beneficial effects, most drugs present other types of effects, which are impossible to avoid, even if only some people express them. These are usually side effects, which appear on the leaflets for each drug.

The manufacture and sale of drugs is authorized by the health authorities, who do not do so until these effects are fully known, and as long as the beneficial effects are much greater than their possible undesirable effects. In addition, there are cases of drug poisoning due to overdose or due to special conditions of the patients.

All these types of effects are known by the generic name of “adverse reactions.”
But there are other types of unpredictable reactions, which only occur in a small number of people, and which are not attributable to the actions of the drug itself, but to the allergic reaction that they trigger in a person in which their immune system makes a response. disproportionate to any of the chemical components of a certain drug. The appearance of these allergic reactions cannot be anticipated during the complicated manufacturing and research process of a medicine, because it depends on the personal response of each individual.

Allergic reactions to drugs are of the utmost importance for the patient, because they cannot be anticipated the first time they occur and because their manifestations can be serious. They can occur at any age, although less frequently in children than in adults. But once presented, it is essential to know against which chemical component it is produced, in order to avoid re-administering it and avoiding new reactions in the future.

Because potentially most drugs can produce allergic reactions, it is advisable not to rule out any as a possible candidate and the list of drugs that the patient usually takes, at the time of the reaction, must be exhaustive.

The time that elapses between taking the drug and the appearance of symptoms helps to decisively classify the type of reaction into immediate and / or late, with important implications for diagnostic attitudes.

The data collected from the clinical history is crucial to be able to carry out an appropriate study, since the design of the same depends on the nature of the adverse reaction, the characteristics of the patient and the drug involved. With all this, the balance between risk benefit is elaborated to choose to carry out the study.

Essential sections in the medical history of a patient with an allergic reaction to a drug:

• Detailed list of all the drugs taken by the patient at the time of the reaction, routes of administration and duration of treatment.
• Investigate prior exposure to suspected medication.
• Time that elapses between taking the medicine and the appearance of symptoms.
• Detailed description of the entire symptom complex, evolution of symptoms as accurate as possible.
• Treatment received to mitigate the allergic reaction.
• Duration of symptoms after stopping the administration of the drug.
• A detailed list of the drugs tolerated after the reaction, makes it possible to rule out some other candidate drugs and simplify the study for the allergist.

Any drug can make them, although some make them more often than others. Whenever epidemiological studies are carried out to know which are the most frequent allergy-causing drugs, the antibiotics of the Penicillin “B-lactam” group appear first, followed by analgesics in general, and within them the most Common are Aspirin and Pyrazolones (Nolotil®), with sensitization to various groups of analgesics, called NSAID Intolerant, and less frequent are reactions with other antibiotics and anesthetics.

Most allergic reactions to drugs have predominantly cutaneous symptoms: Urticaria , Angioedema (edema of soft tissues, eyelids, lips …), Rash, Contact dermatitis, Fixed erythema caused by drugs, or others.

Symptoms of rhinoconjunctivitis, glottis edema, bronchospasm, digestive symptoms (nausea, vomiting, abdominal pain, diarrheal stools), cardiovascular disorders (arterial hypotension, tachycardia, shock) … or others appear less frequently. Anaphylaxis is considered the most serious clinical expression of an allergic reaction, usually defined as a multisystemic disorder with: skin, respiratory, cardiovascular, digestive involvement …

Given that reactions occur in an unpredictable way, we advise that a series of rules be taken into account in relation to the administration of medicines, especially when an adverse effect has already occurred:

• Do not take medications without indication from your doctor, do not self-medicate.
• If in the course of treatment you notice any unexpected reaction, stop the medicine and consult your doctor.
• Always keep the leaflet of the drug that has caused a reaction, as this will facilitate the study in the event of a suspected allergic reaction. The package insert shows the chemical composition of the medicine, including the excipients it contains and which in some cases are the cause of the reaction. If a drug contains several chemicals, the reaction occurs against one of them, so it is essential to know its composition.
• It is also important that you keep the leaflets of the medications tolerated after the reaction, to facilitate the allergological study.
• If you are allergic to a drug, always tell any doctor you see, whatever their specialty.
• If you are allergic to a medicine, keep in mind that it may be part of other commercial preparations with different names, so before taking any medicine, read the package leaflet carefully, and if in doubt, consult your doctor or pharmacist. .
• Not all drug reactions are allergic. Consult with your doctor, who will assess the need for you to be studied by an allergist.