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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Which of the following drug causes least sedation?
assistant
The correct answer is  Loratadine is a second-generation tricyclic H1 histamine antagonist which acts as a selective inverse agonist of peripheral histamine H1-receptors. As a "non-sedating" antihistamine, loratadine causes less sedation and psychomotor retardation than the older antihistamines because it penetrates the blood brain barrier to a smaller extent. Other possible side-effects include headache and antimuscarinic effects such as urinary retention, dry mouth, blurred vision, and gastrointestinal disturbances.