Drug allergy

Drug allergy, more often abbreviated as LA in clinical practice, is a secondary reaction of the immune system to a number of medications. Drug allergy is accompanied by general clinical symptoms and local, local manifestations. As a rule, drug allergy occurs after a period of sensitization, after the immune system "acquaintance" with the allergen. Cases of primary LA are not encountered in clinical practice. That is, an allergic reaction can only occur to a re-introduced provoking drug.

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Why does drug allergy occur?

Drug allergy is a fairly common phenomenon, although half a century ago such manifestations of allergy were extremely rare. People prone to allergies to medications are conventionally divided into two groups:

1. An allergy to a drug occurs after a powerful therapy of the underlying disease. Often this disease is allergic, these include many gastrointestinal pathologies and liver diseases.
2. An allergic reaction occurs as a result of constant contact with medications. These can be pharmacists, doctors, nurses, workers in pharmaceutical factories.

Drug allergy is a serious complication, often leading to a threat not only to health, but also to life. According to statistics, more than 70% of all complications after taking medications are allergies. A fatal outcome occurs in 0.005% of the total number of people suffering from LA. This percentage is very small, which cannot but please, but the risk exists. About 12% of all patients receiving drug therapy suffer from drug allergy. Moreover, these figures are steadily growing due to the general spread of allergic diseases in the world.

Gender preference is also confirmed by statistics. Women react to medications with allergic reactions more often than men. Out of a thousand allergy sufferers who have a histamine reaction due to medications, there are 30-35 women and 14 men. Drug allergy chooses middle-aged people as its target, mainly people from 30 to 40 years old. In most cases, drug allergy occurs after taking antibiotics, which account for 50%. Next comes anti-tetanus serum, which causes a reaction in 25 to 27% of people. Also dangerous for allergy sufferers and others are sulfonamides and NSAIDs - non-steroidal anti-inflammatory drugs. Antiallergic drugs, which are essentially designed to block allergies, can also cause a reaction.

Drug allergy is very insidious and can hide for decades after its “debut” only to relapse at a time when a person has already forgotten about it. Factors that provoke drug allergy:

• Long-term use of the drug, prescription of drugs from the same group, overdose or incorrectly calculated dose;
• Hereditary factor;
• Long-term contact with medications (medical and pharmaceutical workers);
• Mycoses, various types of fungal pathologies;
• History of allergies.

How does drug allergy develop?

There is a concept of full-fledged allergens, these are all substances of protein structure - vaccines, dextrans, serums. These substances react with antibodies, which are produced by the immune system as a response to the invasion. Medicines, on the contrary, combine with proteins and only then become "enemies" - antigens. This is how antibodies are created, when the provoking drug is taken again, the antibodies are grouped into complexes, triggering an allergic reaction. The aggressiveness of medications depends on the chemical composition and the method of administration of the drug into the body. The injection route is most preferable for allergies, the antigen functions faster and the reaction occurs just as quickly. Oral administration of allergy-provoking drugs causes a delayed-type reaction. Subcutaneous administration of the drug sometimes provokes an immediate allergic reaction.

Read also: Allergy to antibiotics

Drug allergy can be true and false. This is anaphylactoid shock, which requires the same urgent resuscitation measures as anaphylactic allergic shock. Anaphylactoid reaction occurs without sensitization, the antigen-antibody complex is absent in the body and the cause of the reaction lies in a completely different area. Pseudo-drug allergy can be distinguished by the following signs:

• Allergy occurs after the first dose of the drug;
• The clinical picture may also manifest itself when taking a placebo;
• Identical manifestations, reactions to drugs of completely different groups according to purpose and mechanism of action;
• An indirect argument for differentiation is the absence of an allergic history.

How does drug allergy manifest itself?

Drug allergies manifest themselves with varying degrees of severity and at different speeds:

• Instant reactions - within an hour.
  • Anaphylactic shock;
  • Acute urticaria;
  • Quincke's edema;
  • Acute hemolytic anemia;
  • Bronchospasm.
• Subacute reactions - within 24 hours.
  • Thrombocypenia;
  • Fever;
  • Maculopapular exanthema;
  • Agranulocytosis.
• Delayed reactions - within two to three days.
  • Serum sickness;
  • Vasculitis and purpura;
  • Polyarthritis and arthralgia;
  • Lymphadenopathy;
  • Nephritis of allergic etiology, allergic hepatitis.

Drug allergy is diagnosed based on clinical manifestations, which often manifest very clearly. Specific therapy is prescribed, which eliminates health- and life-threatening symptoms, and, of course, the drug that provokes the allergy is discontinued. Non-specific therapy is aimed at managing the entire cycle of allergic reactions.

In general, drug allergy is a disease that can be caused by:

• anamnestic individual predisposition;
• incorrect prescription of drug therapy;
• incorrect use of the drug by the patient himself;
• self-medication.