Other common adverse effects in first-generation H-antihistamines include dizziness, tinnitus, blurred vision, euphoria, uncoordination, anxiety, increased appetite leading to weight gain, insomnia, tremor, nausea and vomiting, constipation, diarrhea, dry mouth, and dry cough.Infrequent adverse effects include urinary retention, palpitations, hypotension, headache, hallucination, and psychosis.-receptors and have a better tolerability profile compared to the first-generation agents.Once released, the histamine can react with local or widespread tissues through histamine receptors.
Sold over the counter (OTC), they are less expensive than prescription nonsedating antihistamines. Nonsedating antihistamines, also called new, or second-generation antihistamines, are just as effective against nasal allergy symptoms as older medications. They make you less sleepy and groggy, and are less likely to cause problems with increased eye pressure, which may worsen glaucoma symptoms.
Significant anticholinergic adverse effects, as well as sedation, are observed in this group but the incidence of gastrointestinal adverse effects is relatively low.
The isomerism is a significant factor in the activity of the agents in this group.
Antihistamines are used in the treatment of allergic reactions, colds, hay fever, hives, and insect bites and stings.
Some antihistamines may also be helpful in reducing anxiety, inducing sleep, or at preventing or treating motion sickness.