E2: GI Drugs Flashcards
What are the antibiotics effective for treating for H. Pylori?
Metronidazole, amoxicillin, tetracyclines, and clarithromycin
What 3 things stimulate gastric acid secretion?
Gastrin, ACh, and histamine
How do NSAIDS increase risk of gastric ulcers?
They interfere with formation of prostaglandins (which reduce acid secretion and increase mucous production)
What kind of drugs are magnesium hydroxide and aluminum hydroxide?
Antacids
What are the side effects of magnesium hydroxide?
It increases gastric motility and may cause diarrhea
What are the side effects of aluminum hydroxide?
Relaxes smooth muscle, decreases gastric motility, and may cause constipation
Magnesium hydroxide should be avoided in what patients?
Patient with impaired renal function
What kind of drugs are cimetidine, randitidine, famotidine, and Nizatidine?
H2 blockers
What are the uses of H2 blockers?
- decreasing nocturnal acid formulation
- treatment of duodenal and gastric ulcers, adjuncts for GERD and ZES
- Per-operatively to decrease acid content
- prevent development of ulcers from stress
- used in severe allergic reactions to decrease H2 mediated vasodilation
What are the side effects of chronic cimetidine use?
At high doses, has an anti androgen effect, loss of libido, impotence, gynecomastia, but can be used to treat masculinization in females
What are the drug interactions with cimetidine?
Cimetidine inhibits CYP3A4 so this is important for drugs with low therapeutic range, like warfarin, phenytoin, theophylline, phenobarbitals, some benzos, propanol, digoxin, and TCAs
** other H2 blockers do no inhibit CYP3A4
What is the MOA of PPIs?
- Irreversibly inhibit the proton pump that is the final stage in production of gastric acid.
- Prodrugs that become activated in gastric parietal cells and then bind irreversibly to H+, K+ ATPase
What is the DOC for GERD with esophagitis?
PPIs
What kind of drugs are omeprazole and Esomeprazole?
PPIs
What are the adverse effects of PPIs?
- nausea, diarrhea, abdominal pain
- cough, URI
- Decrease absorption of Ca+, increasing risk of osteoporosis
- magnesium and B12 deficiency
- Long term use have slightly increased risk of CKD
What are the drug interaction with omeprazole?
Omeprazole inhibits CYP2C19, decreasing metabolism of phenytoin, diazepam, and warfarin
-conversion of clopidogrel to the active component may be inhibited
What is the DOC for initial and maintenance treatment of GERD?
PPIs
What kind of drug is Misoprostol?
A Prostglandin E1 analogue that increases secretion of mucous and decreases acid secretion
What is the use of Misoprostol?
Approved for prevention of NSAID induced ulcers, but rarely used due to availability of more convenient and safer drugs
What are the contraindications to Misoprostol?
Since it is a PG analogue, it can induce uterine contractions and abortion is pregnant women. Contraindications in women who are pregnant or may become pregnant while taking the drug
What are the 3 prokinetic drugs for the GI tract?
Erythromycin, Metoclopramide, and bethanechol
How does erythromycin stimulate GI activity?
The neural regulation of gastric motility involves stimulation of cholinergic neurons, inhibition of adrenergic neurons, and modulation of DA and serotonin. Erythromycin stimulates these receptors
How does Metoclopramide increase GI activity?
It is a Dopamine D2 receptor antagonists and since DA in the GI tract acts to decrease motility, inhibiting DA will increase activity
What are the uses of Metoclopramide?
- enhances motility and tone of smooth muscle in the GI tract likely by increases ACh
- Antiemetic
- Use for Post surgical gastric hypomotility
- EPS, GI cramping, and diarrhea side effects
Is Metoclopramide safe is pregnancy?
No
What is the MOA of bethanechol?
-Mucarinic agonist that increases tone and motility of the GI tract
What are the uses of bethanechol?
Used to treat postoperative ileus or to increase lower esophageal sphincter tone
What drug is frequentl used as a prokinetic agent in patients with diabetic gastroparesis or small bowel dysmotility? Why?
Erythromycin or other macrolides because they stimulate receptors for motilin, a peptide which causes potent contraction of the GI tract
What are the two antispasmodics used for irritable bowel syndrome?
Dicyclomine and Amitripyline
How does Dicyclomine treat IBS?
Muscarinic antagonist use to decrease intestinal over activity and reducing cramping/spasms
** anticholinergics side effects: dry mouth, constipation, sedation, etc
How does Amitripyline treat IBS?
Blockade of muscarinic receptors decreases spasticity and increases central NE release, which stimulates alpha 2 receptors to reduce chronic pain
How is the vomiting center in the brain stimulated?
Chemoreceptor trigger zone (CTZ)which is rich in 5HT3 receptors, D2 receptors, neurokinin and opioid receptors
What is the MOA of Zofran?
-selectively blocks 5HT3 receptors in the CTZ and in the GI tract
What is the use of Zofran?
- treatment of nausea and vomiting due to chemotherapy and vagal stimulation
- Not effective for motion sickness
**no significant side effects and not sedating
What is the MOA of Prochloperazine and Promethazine?
Blocks D2, muscarinic, and H1 histamine receptors.
What is the use of Prochlorperazine and Promethazine?
Used for post operative nausea and vomiting, as well as nausea and vomiting due to other causes
**signifcant sedation due to blockade of histamine and muscarinic receptors
What kind of drug is Dronabinol and what is it used for?
a form of THC, the active compound in marijuana.
-Effective antiemetic and appetite stimulant and used for chemotherapy induced nausea and vomiting
What is the MOA of Aprepitant?
-Blocks NK1 receptors and are combined with a 5HT3 antagonist and corticosteroid for severe chemotherapy induced nausea and vomiting
What are the contraindications to laxative use?
Intestinal blockage, perforation, or toxic megacolon
Why is chronic use of laxatives harmful?
May cause electrolyte imbalance, dependence, and serious alterations in bowel function
How do bulk forming laxatives work?
Increase bulk of the feces by attracting water, forming a soft mass that stimulates the wall of the GI tract and induces peristalsis
What is the best way to prevent constipation and diverticulitis?
High fiber diet
What kind of drugs are dietary fiber ad Psyllium?
Bulk forming laxatives
Which bulk forming laxative contains fibrous material from plantago seeds?
Psyllium
What are the common sid effects of bulk forming laxatives?
Bloating and flatulence
-Imporant to consume enough water with these because fecal impact ion may occur with inadequate water
What kind of drugs are magnesium hydroxide, lactulose, and polyethylene glycol?
Osmotic laxatives
Although lactulose is used as an osmotic laxative, what else is it commonly used for?
To decrease ammonia buildup in patients with cirrhosis and other hepatic diseases
What is the MOA of osmotic laxatives?
-Poorly absorbed salts or sugars that hold water in the intestine, speed transfer through the intestine and usually cause fluid evacuation in 1-6 hours
How is polyethylene glycol administered?
Nasogastric tube or orally, often in prep for colonoscopy
-Now available OTC as Miralax for treatment of occasional constipation
Are osmotic laxatives safe for chronic use?
With the exception of lactulose for liver disease, they should not be used chronically. They can produce intense effects
What kind of drugs are Biscodyl and Senna?
Irritants which stimulate peristalsis by action on the mucosa, either by irritation or excitation of the reflexes, enhance secretion and inhibit water reabsorption
What are the uses of laxatives in general?
- Reduce straining
- maintain soft stools in patients with abscesses, hemorrhoids, etc
- Empty out the bowel to prepare for surgery
- acute functional constipation
What are the contraindications to laxative use?
Nausea, vomiting, abdominal cramping ,undiagnosed abdominal pain, appendicitis, or intestinal obstruction
What are the adverse effects of chronic laxative use?
Laxative dependence, fluid and electrolyte imbalance, spastic colitis, and increased risk of UC
What is the MOA of Lubiprostone?
-PG E1 derivative, which increases intestinal fluid secretion by activating specific CIC-3 chloride channels in the luminal cells of the intestinal epithelium
What are the uses of Lubiprostone?
- Softens stools, increase intestinal motility, promotes spontanous bowel movements within 24 hours
- reduces symptoms of chronic constipation
- approved for women with IBS and constipation
What is the MOA of Linaclotide?
-Stimulates intestinal chloride secretion by activating guanylate cyclase C on the luminal surface, this activates cystic fibrosis transmembrane conductor (CFTR), increasing Cl- secretion.
What are the uses of Linaclotide?
-Approved for treatment of chronic constipation and forIBS with constipation
What is the MOA of Loperamide?
Opioid analogue that decreases peristalsis.
-Used for diarrhea
What are the adverse effects of Loperamide?
- At therapeutic doses, has not CNS effects and this low abuse potential.
- Abdominal pain/distention, constipation, dry mouth, hypersensitivity, nausea, and vomiting
What are the contraindications to opioid use for diarrjea?
- Should not be used in diarrhea caused by organisms that penetrate the intestinal mucosa
- UC, may cause toxic megacolon
- Abuse potential, so dont use if hx of drug abuse
What is the MOA of colloidal bismuth compounds (Pepto)?
- Absorbs excess water and possible some microbial toxins and destroy some pathogens
- Inhibits PG synthesis, decreasing secretion and exerting an anti-inflammatory effect
What are the contraindications to Salicylate?
Patient who are allergic o aspirin and in children due to risk of Reye’s syndrome
Sulfasalazine is often used to for what condition?
UC, less often for Crohns
What is the MOA of Simethicone?
Antiflatulent that coats and dissipates gas to make it pass with less of a notice
