Atropine blocks prokinetic effect of metoclopramide but not domperidone Why?
Atropine is an anticholinergic medication that blocks the effects of acetylcholine, a neurotransmitter involved in various physiological processes, including gastrointestinal motility. Metoclopramide and domperidone are both prokinetic medications used to enhance gastrointestinal motility and treat conditions such as gastroparesis.
The prokinetic effect of metoclopramide is partially mediated by its antagonistic action on dopamine receptors in the central nervous system. It also has peripheral effects by increasing acetylcholine release in the gastrointestinal tract and sensitizing the smooth muscle to its effects. The release of acetylcholine and its subsequent binding to muscarinic receptors in the gut promotes increased motility.
Atropine, being an anticholinergic agent, blocks the muscarinic receptors that are activated by acetylcholine. By blocking these receptors, atropine can inhibit the prokinetic effects of metoclopramide. It counteracts the effects of increased acetylcholine release and reduces smooth muscle stimulation, resulting in decreased gastrointestinal motility.
On the other hand, domperidone works primarily by blocking dopamine receptors in the gut, which results in an increase in acetylcholine release and enhanced gastrointestinal motility. Unlike metoclopramide, domperidone does not have significant central nervous system effects. Atropine does not directly interfere with the dopamine receptors targeted by domperidone. Therefore, the prokinetic effect of domperidone is not affected by atropine administration.
It’s important to note that the interactions between medications can be complex and may vary based on individual factors. The specific effects and interactions of medications should be discussed with a healthcare professional or pharmacist to ensure safe and effective use.