GI Pharm 1 Flashcards
Antiemetics
- Classes of drugs
- neurotransmitter receptor sites involved in the vomiting reflex
Classes
- Anticholinergics
- Antihistamines
- Dopamine Receptor Antagosists
- -Phenothiasines
- -Benzamides
- Serotonin antagonists
NT sites
- M1: muscarnic
- D2: Dopamine
- H1: Histamine
- 5-hydroxytryptamine (HT)-3
- -serotonin
- Neurokinin 1 (NK1) receptor
- -Substance P
Anticholinergic Agents
- receptor
- main drug in this category
- route of admin
- SE
Receptor
-M1 - mucarinic
Main Drug
-Scopolamine (used as prophylaxis agaist motion sickness
Route
-transdermally
SE
-dry mouth, drowsiness, vision distrubance
Antihistamines
- receptor
- drugs
- primary use
- SE
Receptor
-H1 blockers
Drugs
- diphenhydramine (Benadryl)
- Cylisine (cyclivert)
- Dimenhydrainate (Dramamine)
- Meclizine (dramamine less drowsy)
Primary use
-motion sickness
SE
- sedation
- anticholinergic SE
Dopamine Receptor Antagonists
-3 subclasses and their drugs
Phenothiazines*
- Prochlorperazine (Compazine)
- Promethazine (Phenergan) (could also be classified as an antihistamine)
- first line agents
Butyrophenones
-Antipsychotics
Bensamides*
- Metachlopramide (Reglan)
- Trimethyobenzamide (Tigan)
Phenothiazines
- drugs
- routes of admin
- work on which receptors
- SE
Drugs
- Prochlorperazine (Compazine)
- Promethazine (Phenergan)
Routes
-oral, rectal, IV
Receptors
-have antagonistic properties at D2, H1, and M1 sites
SE
- extrapyramidal rxn (dystonia)*
- tardive diskinesia*
- hypotension*
- sedation, drowsiness, anticholinergic effects
- use with caution in elderly, with other CNS depressants, poorly controlled sz, severe liver dz
*Acute dystonia can be treated with diphenhydramine 25-50mg IV or IM
Bensamides*
Metachlopramide (Reglan)
- receptors
- MOA
Trimethyobenzamide (Tigan)
-MOA
Metachlopramide (Reglan)
Receptors
- central and peripheral dopamine D2 antagonism at low doses
- weak 5-HT3 blockade at higher doses
MOA
-stimulates cholinergic receptors on gastric smooth muscle cells and enhances acetylcholine release at the NMJ
Trimethyobenzamide (Tigan)
MOA
- Unclear, works CENTRALLY in the area of the medulla oblongata
- considered the most potent antiemetic that does not have effects on the serotonergic, dopaminergic, or histamine systems, so it has a lower likelihood of causing undesired SE
Serotonin 5-HT3 Antagonists
- receptors
- clinical use
- SE
- Drugs
Receptors
-5-HT3-receptor blockade
Clinical Use
- great for postoperative and chemotherapy induced nausea and vomiting
- not great for nausea secondary to vestribular system etilogy (vertigo)
SE
- HA, dizziness, constipation
- generally well tolerated
Drugs
- Ondansetron (Zofran)***
- Granisetron (Kytril)
- Dolasetron (Anzement)
- Palonosetron (Aloxi)
Zofran (odansetron)
- Approved for use in adults?
- Approved for use in children?
- Pregnancy category?
- Drug Interactions
- routes of admin
- Approved for use in children and adults
- Pregnancy Cat B
Drug Interactons
-caution for serotonin syndrome, QT prolongation, Monitor liver function tests if prolonged use
Routes
-Solution (IV) or tablets (PO)
*Zofran is typically for short term use. Its somewhat expensive
Antiemetic drug selection should be based on the underlying disorder. N/V associated with chemotherapy is treated differently, what is a helpful adjunct?
Dexamthasone is helpful in treating Chemo n/v
Abx for tx of Infectious Diarrhea
Empiric Abx Therapy
first line: Ciprofloxacin (oral FQ)
Second line: oral macrolide (Azithromycin)
What are the rules for pharmacologic therapy for the symptomatic treatment of diarrhea?
If there is NO fever AND NO blood in stool, then you can use an anti-motility agent to decrease the number of stools per day
Anti-diarrheal: Bismuth subsalicylate
- aka
- MOA
- SE
- Caution
- CI
- use
AKA
-Pepto-Bismol
MOA
- considered an absorbent
- stimulates absorption of fluid and electrolytes across the intestinal wall but also when hydrolyzed to salicyclic acid, inhibits synthesis of a prostaglandin responsible for intestinal inflammation and hypermotility
SE
-dark stools, black tongue
Caution
- do not take with other ASA compnents
- can potentiate anticoagulants
CI
- ASA allergy
- infants and children
Use
-good for travelers diarrhea
Anti-diarrheal: Loperamide (Imodium)
- MOA
- preg cat
- duration of use
- SE
MOA
- acts directly on circular and longitudinal intestinal muscles, through opiois receptor
- -inhibits peristalsis and prolongs transit time
- -reduces fecal volume, increases viscosity
- -diminishes fluid and electrolyte loss
- -demonstrates antosecretory activity
- -Increases tone on the anal sphincter
Preg Cat C
Don’t use loner than a few days, need to reevaluate pt
SE
-abd pain/distention, constipation, dry mouth, nausea, dizziness, drowsiness
*Avoid if enteroinvasive organism is suspected
Anti-diarrheal: Dipenoxylate/atropine (Lomotil)
- MOA
- Preg Cat
- prescription or OTC
- SE
MOA
- Opiod antagonist and anticholinergic
- -inhibt peristalsis and slows intestinal motility
- -inhibits GI propulsion
- -Prolongs the movement of fluid and electrolytes through the bowel
Preg Cat C
Prescription
SE
- Paralytic ileus, toxic megacolon
- drowsiness, dizziness
- euphoria
- tachycardia
- pruitis, urticaria
- resp depression
- anticholinergic effects
*Avoid if enteroinvasive organism is suspected
Cholestyramine (Questran)
- Preg Cat
- MOA
- Useful when
- directions
Preg Cat C
MOA
-bile acid-binding agent used for hyperlipisemia
Useful
-for the tx of chronic diarrhea post cholecystectomy
Directions
-1 scoop mixed with fluid or foods BID
SE
- constipation
- abd apin/bloating
- vomiting
- excessive flatulence, diaarrhea
- weight loss
- decreased absorption of warfrin, thyroid hormones, digoxin, and thiazide diuretic
