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When we need to use drugs to reduce allergies, we often think of antihistamines first. So what is the mechanism of this group of drugs, and how is it appropriate to use drugs?
1. What is Histamine?
Histamine is an intermediary that plays an important role in allergic reactions. Target effects of histamine in the body include H1 histamine receptors (found in many different types of cells such as respiratory smooth muscle, blood vessels, white blood cells ...) and H2 receptors (present in parietal cells. stomach). When allergens enter the body, the released histamine acts on H1 receptors, causing allergic reactions (edema, inflammation, itching, rash, tracheal spasm ...). When acting on H2 receptors, histamine causes increased secretion of gastric juice, if too much can cause stomach ulcers.
2. Antihistamines
Antihistamines are antagonists that compete with histamine at their respective receptors. Depending on the antagonism that takes place on H1 or H2 receptors, we divide antihistamines into 2 types: one is an anti-allergic H1 antihistamine and the other is an H2 antihistamine that helps reduce stomach acid secretion. In the treatment of allergies, H1 antihistamines are usually the first and safe choice, while H2 antihistamines are used to reduce acid secretion and treat stomach ulcers.
2.1 Antihistamine H1
There are many types of H1 antihistamines on the market, including 2 main groups: 1st generation and 2nd generation drugs.
2.2 H2 antihistamines
Typical H2 antihistamines such as cimetidine, famotidine, ranitidine ... are used in the treatment of stomach ulcers - duodenum, gastroesophageal reflux. The possible side effects when taking the drug include diarrhea, headache, dizziness ... However, these reactions are rare and the drug is considered safe for most people taking the drug.
3. How to use H1 antihistamine?
H1 antihistamines are indicated in the treatment of acute and chronic allergic reactions with symptoms such as runny nose, erythema, rash, urticaria, atopic dermatitis ...
However, antihistamines only help relieve symptoms, do not change the cause of the disease, so identify and avoid allergens (such as pollen, dust, food, medicines, cosmetics. other ...) to help cure the disease completely. However, in some cases, finding the cause of the disease requires the understanding and examination of the treating doctor for the best effect.
In the case of patients with severe allergies (such as anaphylaxis), histamine is released massively, only H1 antihistamines cannot be resolved, but must quickly bring the patient to the emergency room for appropriate treatment.
In addition, a number of first-generation drugs are also used as anti-motion sickness drugs due to their sedative and mild sedative effects, helping to alleviate vestibular disorders, dizziness and nausea.
4. Things to keep in mind when using H1 antihistamines
1st generation H1 antihistamines have side effects on the central nervous system such as drowsiness, distraction, dizziness, so should not be used while driving a vehicle, working at high altitude, operating machinery. or jobs that need alertness. The first generation drugs also cause dry lips, constipation, tachycardia, and urinary retention when used for a long time. Generation 2 H1 antihistamines have less of these side effects than 1st generation drugs.
In summary, H1 antihistamines are effective in reducing symptoms caused by allergies such as itching, runny nose, etc. Allergy and urticaria. With a long history and proven safety over the years, antihistamines are widely used and effective over-the-counter drugs for treatment.
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