Antihistamine drugs antagonise the action of histamine and are therefore of value in the treatment of certain allergic conditions. They may be divided into those which have an effect on the brain (e.g. flupheniramine and cyclizine) and those such as loratidine and terfenadine, which have little or no such action. Antihistamines are also of some value in the treatment of vasomotor RHINITIS; they reduce rhinorrhoea and sneezing but are usually less effective in relieving nasal congestion. All antihistamines are useful in the treatment of urticaria and certain allergic skin rashes, insect bites and stings, as well as in the treatment of drug allergies. Chlorpheniramine or promethazine injections are useful in the emergency treatment of angiooedema and anaphylaxis.
Antihistamines refer to a class of medications that inhibit the effects of histamine, a chemical released during allergic reactions.
Antihistamines are utilized for the treatment of skin rashes like urticaria (hives) and to alleviate symptoms of sneezing and a runny nose in allergic rhinitis. Additionally, they are occasionally incorporated into cough and cold remedies. These medications also serve as antiemetic drugs, as they suppress the vomiting reflex. Typically, antihistamines are taken orally, but in cases of anaphylactic shock, they may be administered via injection.
Antihistamine medications hinder the impact of histamine on various tissues, including the skin, eyes, and nose. In the absence of drug intervention, histamine has the ability to widen small blood vessels, leading to inflammation in the surrounding tissues as fluid leaks from the circulation. Antihistamines additionally prevent histamine from stimulating nerve fibers, thereby alleviating itching sensations.
While numerous antihistamines are associated with drowsiness as a common side effect, newer medications tend to have minimal sedative effects. Other infrequent side effects may include reduced appetite, nausea, dry mouth, blurred vision, and urinary retention (difficulty in passing urine).
While undergoing antihistamine treatment, it is crucial for individuals to refrain from driving or operating hazardous machinery unless they are certain that the medication does not induce dizziness, drowsiness, or impaired concentration. Safety should always be prioritized.