Antihistamine Drugs: Mechanisms, Clinical Applications, Side Effects, and Emerging Formulations
Antihistamine drugs block the effects of histamine, a chemical mediator in allergic reactions, gastric acid secretion, and neurotransmission.
They are widely used for treating allergies, urticaria, hay fever, anaphylaxis, and gastrointestinal disorders such as peptic ulcers. Antihistamines are classified into H1, H2, H3, and H4 receptor blockers based on their site of action, each targeting different physiological pathways.
H1 antagonists alleviate allergic symptoms such as sneezing, itching, and nasal congestion. H2 blockers reduce gastric acid production in ulcers and gastroesophageal reflux disease (GERD). H3 and H4 antagonists, under investigation, show promise for neurological disorders, inflammation, and autoimmune conditions. Formulations include oral tablets, syrups, nasal sprays, and injectables, with both first-generation (sedating) and second-generation (non-sedating) options available.
Emerging trends focus on long-acting formulations, combination therapies, and targeted delivery systems. Safety considerations include drowsiness, dry mouth, headache, and potential drug interactions. Patient education is critical to ensure proper dosing, adherence, and management…