GI: Prokinetics and Antidiarrheal Flashcards
Outer longitudinal muscle
Peristalsis (aboral movement, unidirectional)
Myenteric plexus (Cholinergic affects)
Peptide hormone (motilin)
Inner circular muscle
Segmentation contraction (narrowed lumen and mixing)
Submucosa plexus
Cholinergic and adrenergic effects
Risk of diarrhea
Peristalsis > segmentation contraction
Risk of constipation
Segmentation contraction > peristalsis
Drugs regulating peristalsis
Cholinergics
Dopamine antagonists (Ach sensitizer)
Miscellaneous
Contrain: GI obstruction!!
Cholinergics
Bethanechol, Neostigmine
Ranitidine, nizadidine
Cisapride
Bethanechol (urecholine) MOA
Cholinergic agonist
Binds to muscarinic receptors and initiates smooth muscle contraction
Bethanechol uses
Gastric emptying in horses
↑ Ileocolic contraction in cattle
↑ bladder smooth muscle contraction
Bethanechol adverse effects
Non-specific binding (pleotrophic)
Profound sid effects
Diarrhea
Neostigmine (prostigmin) MOA
Acetylcholinesterase inhibitor
Inhibits degradation of Ach (stimulating cholinergic receptors)
Neostigmine uses
Myasthenia gravis
Large colon motility (equine)
Ranitidine and Nizatidine MOA
H2 blockers and inhibits AcholE
Cisapride MOA
Enhances Ach release
Agonist for 5-HT4 receptor
Dopamine antagonists (Ach sensitizer)
Metoclopramide (reglan), doperidone
Metoclopramide MOA
Antagonist: dopamine and 5HT3 centrally
Agonist: 5HT4
↑ release of Ach