system
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
Clonidine is used as an antihypeensive agent but if used as a fast intravenous injection, it can increase the blood pressure due to:
assistant
The correct answer is  Alpha 2 receptors are present both presynaptically as well as postsynaptically. Clonidine acts as presynaptic a2 agonist and decreases the central sympathetic outflow. However, it can also act on vascular postsynaptic a2 receptors, leading to vasoconstriction and increase in blood pressure. Chances of this reaction is more when clonidine is administered by quick i.v. injection.