Antihistamines replace histamine of the two receiver sites where it becomes bound to various vulnerable tissues, thus stopping histamine-triggered reactions under such circumstances as stress, inflammation, and allergy.
The antihistamines that were the first to be presented are ones that fix at the so-called H1 receiver sites; they are therefore selected H1-blocking agents and face selectively all the pharmacological properties of histamine except those on stomach secretion. The development of these antihistamines dates from 1937, when French scientists discovered compounds that protected animals against both the deadly effects of histamine and those of deadly shock. The first antihistamines were byproducts of ethylamine; aniline-type mixtures, tested later and found to be more powerful, were too poisonous for clinical use. In 1942, the forerunner of modern antihistamines was discovered; then, mixtures that were more potent and less toxic were made. More than 100 antihistaminic mixtures soon became available for treating patients.
Since histamine is involved in the making of some symptoms of allergy, antihistamines can control certain allergic circumstances, among them hay fever and seasonal rhinitis; the nasal irritation and watery release are gladly relieved. Persons with urticarial, edema, itching, and certain sensitivity responses respond well. Antihistamines are not usually helpful in treating the common cold and also asthma. Antihistamines with powerful antiemetic assets are used in the treatment of vomiting. Used in sufficiently large amounts, nearly all antihistamines produce unwanted side effects; the incidence and harshness of the side effects rely both on the patient and on the properties of the exact drug. The most common side effect in adults is sleepiness. Other side effects consist of stomach irritation, headache, blurred vision, and a dry mouth. If a patient’s illness does not improve after three days of treatment with antihistamines, it is unlikely that he/she will profit from them. Antihistamines are gladly absorbed from the alimentary tract.
© copyright Isaiah Schultz 2011