Antihistamines are a pharmacological group of drugs that inhibit the activity of specific histamine receptors in the cells of the body. The effect of these drugs is to eliminate the spasm of the smooth muscles of the intestines and bronchi, reduce the permeability of capillaries, facilitate the flow of allergic reactions, and prevent tissue edema.
Antihistamines are usually available over the counter. These drugs include Brompheniramine, Chlorpheniramine, Clemastine, Diphenhydramine, Loratadine.
Prescription drugs: Cetirizine, Desloratadine, Foxofenadine. These drugs practically do not cause side effects, which are manifested by dry mouth or drowsiness.
Antihistamines are classified into three groups according to their structure: ethylenediamines, ethanolamines, alkylamines, piperazines, tricyclides. The first, second type of drugs causes a characteristic side effect - drowsiness, which somewhat limits their use. To eliminate this drawback, alkyl amines have been developed. They are used to stop the symptoms of colds: lacrimation, sneezing, runny nose. The purpose of using piperazines is to affect the parts of the brain that are responsible for the occurrence of feelings of motion sickness, dizziness, nausea, and vomiting. Antihistamines for pregnant women - tricyclics. They are used to treat toxicosis, to obtain a sedative effect. All these groups of drugs in medical practice are combined into first-generation drugs.
Today, a significant number of experiments and trials of drugs. Based on them, two new generations of antihistamines were isolated. They differ in chemical composition and the number of side effects. Third generation antihistamines act only on target organs, do not affect other body systems. They were developed to treat Alzheimer's.
The mechanism of action of drugs of this pharmacological group is the displacement of histamine from tissue systems, blocking the receptors of gland cells and smooth muscles. As a result, an obstacle is created for the occurrence of allergy symptoms . Medicines are most effective when taken continuously.
Contraindication for antihistamines is hypersensitivity to their active substances. The occurrence of undesirable effects in cases of administration and by monooxidase inhibitors is observed. It is also not advisable for patients with glaucoma and nursing mothers to use these medicines (before use, a mandatory doctor's consultation is necessary). Currently developed antihistamines for infants, which in composition are similar to substances of the third generation. They cause minimal side effects and do not affect the metabolic processes of the body.
Antihistamine drugs are available in the form of a liquid, tablets, capsules. The frequency of reception directly depends on their type and features.
Medicinal substances can not be combined with drugs that have a sedative effect, since they significantly enhance it. These drugs include tranquilizers. It is not recommended to combine antihistamines with monoxidase inhibitors, phaselin sulfate, tranicylcypromil.
Specific side effects of the substances of this drug group are dry mouth, drowsiness, urinary retention, loss of visual acuity.