The drug after combining with the body protein may be an antigen (allergen), causing the formation of specific antibodies directed against each other.
THE ALLERGY ARGENT MECHANISM
Drugs may cause hypersensitivity reactions and allergic reactions.
A typical allergic reaction is possible when the drug is already associated with the body protein. Then it occurs as an allergen, and the reaction proceeds with the participation of the immune system. In other cases, these are hypersensitivity reactions - induced by toxically disturbed metabolic changes occurring without the involvement of the immune system or caused by a defect or deficiency of an enzyme.
How a sensitizing allergen arises from the drug
Most drugs have hapten properties, i.e. they form the right antigen when combined with the body protein. As we know, the protein structure is characterized by allergens. The time required to produce hyperreactivity to the allergen is 1 - 3 weeks.
What determines that the drug - allergen is highly sensitizing?
Sensitizing properties depend to a large extent on the chemical structure of the drug. Heavy metal compounds, sulfonamides, some antibiotics (especially penicillins), analgesics, especially salicylates, (especially topically applied to the skin), iodine compounds, and others, have particularly strong allergenic properties. In addition, the most frequently sensitizing drugs include protein preparations - e.g. immune sera, hormones and antibiotics. It should be remembered that sensitization may also cause auxiliary components contained in the tablet or ointment, eg preservative or dye. The occurrence of allergy symptoms does not depend on the route of administration of the drug, but after parenteral administration the reactions are more turbulent. People with allergies are more susceptible to allergy to medication.
The most common symptom of allergy to the drug are skin changes:
The most important of these are maculopapular changes, acute urticaria and edema, contact dermatitis, erythema multiforme, photoallergic reactions, and persistent erythema.
What are the most common causes of these skin changes?
- Urticaria - in the form of itchy blisters and vasomotor edema. If the swelling affects the face, it distorts its contours, and if the airways, it can lead to shortness of breath. Urticaria may be caused, for example, by aspirin, ampicillin.
- mottled-spinal rashes - are very common, next to urticaria, with drug-induced skin reaction. They usually appear after a few days of using the medicine. A classic example is the rash of ampicillin or sulfonamides.
- Erythema multiforme - it happens quite often. The eruptions are well-delineated erythema of various shapes, which mainly include the upper and lower limbs, and less often the trunk. They can stay on the skin for a few weeks. Appears after penicillins or sulfonamides.
- Contact eczema - characterized by the presence of lumps, bubbles and erythema. It develops most often under the influence of skin contact with a sensitizing drug.
- Leg cramps - develops in the elderly or with varicose veins. Leg ulcers often accompany them. This eczema persists for many years, and sensitizing drugs are often used to treat varicose veins or ulcers, for example: neomycin, Peru balsam, essential oils, propolis, rivanol, lanolin, anestezin, detreromycin.
- Systemic eczema - takes two forms. It can only include the feet and hands on which there are numerous vesicles or cover the area of the buttocks, where the inflammation of the skin develops.
OTHER IMPORTANT SYMPTOMS OF ASKINGS
Other symptoms of drug allergies are:
- bronchial asthma - most often caused by anti-inflammatory drugs, especially aspirin.
- allergic rhinitis very often coexists with bronchial asthma.
- conjunctivitis manifested by their congestion and edema. Fortunately, these ailments do not pose a threat to the eyes. They are often caused by ophthalmic drugs in drops: antibiotics (neomycin, gentamicin), anti-glaucoma drugs (beta-blockers), as well as their preservatives.
Drug allergy can lead to pathological changes in blood counts:
- drug-induced anemia
- decrease in the number of platelets
- reduction in the number of white blood cells
Compound anemia
Compound anemia can be triggered, among others by high doses of penicillin, alphaetyldopa, quinidine and cephalosporins.
A decrease in the number of platelets
The decrease in platelet count may be a consequence of using, for example, sulphonamides, quinine, quinidine, heparin, gold salt, paracetamol and propylthiouracil - a medicine against mercury. To lower the number of white blood cells can lead to the use of phenothiazine, sulfonamides, pyramidone, thiouracil and some anticonvulsants.
Life-threatening systemic reactions include anaphylactic shock and drug-induced fever.
