CH 21: GI Meds Flashcards
Nausea and vomiting comes from what?
Drugs, including prescriptions alcohol illness motion sickness head injury ETC
- involves sites in Medulla Oblongata (emetic center or chemoreceptor trigger zone (CTZ)),, including various neurotransmitter systems
Goal of therapy for GI meds
reduce feelings of nausea
reduce incidence of vomiting
Phenothiazines
Prochlorperazine (Compazine);
Promethazine (Phenergan)
- Often used for mental illness; block dopamine receptors in the CTZ, and possibly cholinergic or histaminergic sites
Side effects:
caution in patients taking other meds that cause CNS depression
- tend to cause drowsiness/ sedation
- can lead to extrapyramidal side effects (DA receptors) (drooling, pill-rolling, etc). –> may treat w/ anti-histamines
Anti-histamines
Used for mild nausea/ motion sickness
- Block afferents that stimulate nausea / vomiting
- include:
Hydroxyzine, Meclisine (Bonine), Dimenhydrinate (Dramamine) and Scopolamine
Side effects:
drowsiness; anti-cholinergic side effects (dry mouth, constipation)
Benzodiazepines
(Lorazapam)
- anxiolytics; beneficial for the anticipation of nausea as well as by activating inhibitory receptors in vomiting center
Serotonin-3 receptor blockers
Dolasetron, Granisetron, Ondasetron
Serotonin receptors in CTZ get blocked. Used initially for cancer chemotherapy nausea
- can lead to headache and gastric pain (in some)
Corticosteroids
Used for chemotherapy-induced nausea
- may work through inhibitory for PG’s
Cannabinoids
ONLY for nausea & vomiting associated w/ chemo
- believed to work through THC receptors
Neurokinin 1 antagonists
Aprepitant (interferes w/ vomiting reflexes)
Can be used with:
5HT-3 blockers
Corticosteroids
(Used to treat nausea and vomiting associated with chemotherapy)
- NEWEST class of antiemetics
- Antagonists at the neurokinin type-1 receptors
- Substance P is a neurokinin neurotransmitter that acts through neurokinin type-1 receptors found in the central and peripheral NS to induce nausea & vomiting
- FDA approved when used w/ standard antiemetics to prevent PONV in patients undergoing high ematogenic chemotherapy
What causes GERD
- obesity
- fatty foods, peppermint, chocolate, citrus, tomato, caffeine
- medications
- recumbent position
Medications for GERD
- Antacids:
neutralize stomach acid (thus less reflex to esophagus)
Aluminum hydroxide (Rolaids) (constipation) Calcium carbonate (TUMS) Magnesium hydroxide (diarrhea)
- can get acid rebound»_space; neutral pH stimulates acid secretion
- take 1 (lasts 2 hrs), take another (last 4 hrs)
H-2 Antagonists
- Histamine causes peripheral cells to release HCl in stomach
- Histamine acts at an H-2 receptor to induce this response
Cimetidine (Tagamet), Rantidine (Zantac), Famotidine (Pepcid)
- 90% decrease in acid release
Side effects:
confusion in elderly (rare)
headache
dizziness
Zantac (ranitidine)
- relieves/prevents heartburn & acid digestion
- fast acting
- all day/all night relief
Anti-cholinergics for acid
ACh stimulates proton pump in stomach
Pirenzipine:
Specific for muscarinic receptors in stomach mucosa; blocks secretions w/out dry mouth, constipation, etc of anti- cholinergics
Proton Pump Inhibitors
Prevent proton pump (H+/K+ ATPase) from producing acid
(may also be anti-bacterial to H pylori)
Omeprazole (Prilosec)
Lansoprazole (Prevacoid)
Pantoprazole (Protonix)
- Most effective at treating acid & healing ulcers
can get acid rebound w/ discontinuing usage
Misoprostol
(prost. E1 analog)
- ONLY used to treat ulcers assoc. w/ aspirin (acid inhibitory and mucosa protective)
Sucralfate
disaccharide (sucrose salt)
- polymerizes over ulcers to heal ulceration
Metoclopramide
block DA (D2) receptors centrally (anti-emetic), but also cholinergic that increase GI motility and secretions
(restless, drowsiness)
- can cause extrapyramidal side effects (EPS)
Antibiotics
Used for peptic ulcer disease, the culprit is usually H pylori
Amoxicillin, Clarithromycin, Metronidazole, tetracycline
Algorithm
FOR GERD
- H2 blockers or proton pump inhibitors
- Proton pump inhibitors
Anti- diarrheal’s
A. Opioids:
lead to reduced GI motility
- Diphyenoxylate, Loperamide (Imodium: non-prescription) and Eluxadoline
(no sedation or addiction; don’t cross BBB) - Nausea, gut pain, constipation
B. Adsorbents:
Kaolin and pectin (stick to agents that cause diarrhea)
- constipation over long usage
C. Bismuth salicylate:
absorb water, antibiotic action, decrease PG’s… less motility
Laxatives
“speed up motility”
- some are “bulk-forming” (Metamucil, citrucel)
- bind fecal material and pull H20 into GI tract
- some are stimulants (dulcolax, Senna (Senacot))
- increase smooth muscle motility in GI tract
- some are “hyperosmotics” (glycerin, lactulose, MgOH)
- pull H20 into GI tract
- some are lubricants (mineral oil)
- some are chloride channel activators (lubiprostone)
Cathartics: cause rapid evacuation
Metoclopramide: increase motility
What is Irritable Bowel Syndrome?
- abdominal discomfort that can be relieved w/ defecation
- occurs often after meals: can alternate b/w constipation and diarrhea; bloating, gassiness, distention
Treating Irritable Bowel Syndrome
1st: avoid food that trigger, exercise, and reduce stress
use laxatives/ anti-diarrheal’s as necessary
may also use antispasmodics (anticholinergics), including cicyclomine or hyoscyamine (muscarinic blockers), or the chloride channel activator, Lubiprostone
