GI pharmacology II Flashcards
what is the result of D2 receptor stimulation in the GI smooth muscle?
prevent release of Ach / neuronal firing (decrease motility, negative regulator)
what are the prokinetic agents?
- metoclopramide
- bethanechol
- neostigmine
- erythromycin
what is the mechanism of action of metoclopramide?
D2 antagonist
what is the mechanism of action of bethanechol?
M3 agonist
what is the mechanism of action of neostigmine?
AchE inhibitor
what is the mechanism of action of erythromycin?
motilin receptor agonist
what are the common osmotic agent laxatives?
- magnesium hydroxide
- sorbitol
- lactulose
- polyethylene glycol (PEG)
what are the mechanisms by which stimulant laxatives work?
- stimulation of ENS
- induces leaky mucosa
- inhibition of sodium uptake by gut
what are the common stimulant laxatives?
- anthraquinone (aloe, senna)
- castor oil
- diphenylmethane derivatives
what is the mechanism of action for the serotonin receptor laxatives?
- activation of 5-HT4 receptors promotes NT release in ENS resulting in motility
- decrease firing of extrinsic sensory neurons to the CNS (block pain)
what is the mechanism of action for chloride channel activating laxatives?
- activation of chloride ion channel 2 (CIC2) from luminal side
- increase luminal concentration of chloride in the gut leading to accumulation of sodium and water
- motility and softer stool
what is the effect of mu opioid receptor antagonist laxatives?
prevention of constipation without decrease in pain management (cannot penetrate BBB)
what kind of agent is tegaserod?
laxative - serotonin partial agonist
what kind of agent is lubiprostone?
laxative - chloride channel activator
what kind of agent is methylnaltrexone?
laxative - mu opioid receptor antagonist
what kind of agent is alvimopan?
laxative - mu opioid receptor antagonist
how do opioids alter GI smooth muscle?
- decrease perisaltic contractions
- increased segmental contractions (mixing)
- increased internal anal spincter tone
- decreased perception of GI distension
how do the bismuth antidiarrheal agents work?
inhibition of PG synthesis and absorption of toxins
what kind of agent is octreotide?
somatostatin analog that inhibits motility and promotes fluid absorption
what type of drug is loperamide (Imodium)? what is the mechanism of action?
- antidiarrheal
2. opioid agonist
what type of drug is diphenoxylate (Lomotil)? what is the mechanism of action?
- antidiarrheal
2. opioid agonist
what type of drug is bismuth subsalicylate (Pepto-Bismol)? what is the mechanism of action?
- antidiarrheal
2. inhibits PG synthesis
what type of drug is cholestyramine (Prevalite)? what is the mechanism of action?
- antidiarrheal
2. binds bile salts and bile acids
what type of drug is octreotide (Sandostatin)? what is the mechanism of action?
- antidiarrheal
2. somatostatin receptor agonist
what are the key vestibular receptors involved in the emetic response?
H and M
what type of agent is odansetron (Zofran)? what is the mechanism of action?
- antiemetic - direct
2. 5-HT3 blocker
what type of drug is scopolamine? what is the mechanism of action?
- antiemetic - direct (MOTION SICKNESS)
2. M1 antagonist
what type of drug is metoclopramide (Octamide)? what is the mechanism of action?
- antiemetic - dierct
2. D2 antagonist
what type of drug is dimenhydrinate (Dramamine)? what is the mechanism of action?
- antiemetic - direct (MOTION SICKNESS)
2. H1 antagonist
what type of drug is aprepitant (Emend)? what is the mechanism of action?
- antiemetic - direct
2. NK1 antagonist
what type of drug is prochlorperazine (Compro)? what is the mechanism of action?
- antiemetic - direct
2. M1, D2, H1 antagonist
what type of drug is lorazepam (Ativan)? what is the mechanism of action?
- antiemetic - indirect (anxiety, chemotherapy)
2. GABA agonist
what type of drug is nabilone (cesamet)? what is the mechanism of action?
- antiemetic - indirect
2. cannabinoid agonist
what type of drug is dexamethasone? what is the mechanism of action?
- antiemetic - indirect
2. glucocorticoid agonist
