GI Flashcards
GI medications
- Laxatives and cathartics
- Antidiarrheals
- Antiemetics
- Emetics
- Gastritis and PUD medications
Laxatives and cathartics
- Bulk-producing agents
- Stool softeners / Surfactants
- Lubricants / Emollients
- Hydrating agents/ Osmotic agents
- Hyperosmotic agents
- Stimulants / Irritants
4 main actions of laxatives/cathartics
Increase pressure within the colon (bulk-producing agents)
Lubricate lining of colon (stool softeners and lubricants)
Increase fluid in colon (osmotic agents and hyper-osmotic agents)
Stimulate smooth muscle of colon (stimulant – irritants)
obstruction
Rectal administration of laxatives is preferred over oral administration if there is any question of intestinal obstruction.
• Agents which stimulate peristalsis should always be avoided whenever obstruction is a possibility.
Insoluble fiber
- Insoluble dietary fiber possesses passive water attracting properties that help to increase bulk, soften the stool and shorten transit time through the intestinal tract.
- Sources of insoluble fiber include: whole grain foods, bran, nuts, seeds, vegetables such as green beans, cauliflower, zucchini, celery, and tomato skins.
Soluble fiber
- Soluble fiber undergoes metabolic processing via fermentation, yielding end- products that can improve bowel health..
- Soluble fiber sources include: legumes, oats, rye, barley, fruits (particularly apples and bananas), berries, vegetables, such as broccoli and carrots, and root vegetables, such as potatoes and yams.
Psyllium/ Metamucil
- Category: Fiber laxative
- Indication: Constipation, irritable bowel, reduction of colon cancer risk, reduction of cholesterol levels and heart disease risk.
- MOA: Made from ground psyllium seed husks that contains both soluble and insoluble fiber. Adds bulk to stool and well as absorbing fluid into the feces to soften the stool.
Char: PO. Powder, capsules and wafers. May take several days before therapeutic effect is achieved. Increased oral intake of water may hasten effects.
• Side effects: Usually well tolerated. May cause diarrhea. Avoid use if any suspicion of intestinal obstruction. wafers contain gluten.
Docusate/ Colace
- Category: Stool softener
- Indication: Constipation, hemorrhoids. Prophylaxis in patients who should not strain during bowel movement (i.e. after anorectal surgery, M.I.)
- MOA: Anionic surfactant
- Char: Capsule, Liquid, rectal suppository. The effect on stools is usually seen in 1 to 3 days after the first dose.
Side effects: Usually well tolerated. Flatulence, bloating, abdominal cramping May cause diarrhea. Avoid oral use if any suspicion of intestinal obstruction.
Magnesium Hydroxide/ Milk of Magnesia
- Category: Osmotic laxative, antacid
- MOA: Magnesium salts are poorly absorbed by the GI tract and thus act as osmotic agents to draw water into the lumen of the GI tract.
- Indication: Constipation, indigestion
- Char: PO. Chewable tablets, capsules, liquid. Generally takes 6 hours for therapeutic effects.
Side effects: Diarrhea, cramping, abdominal pain. May precipitate or exacerbate electrolyte imbalances. Patients with severe chronic kidney disease are at greater risk for possible hypermagnesemia. Avoid use if any suspicion of intestinal obstruction.
Bisacodyl/ Dulcolax

- Category: Stimulant laxative
- MOA: Increases intestinal motility.
- Indication: Constipation
- Char: PO. Generally takes 2 to 6 hours to work.
- Side effects: Diarrhea, abdominal cramping, sweating. Possible laxative dependence with prolonged use. Definitely avoid use if any suspicion of intestinal obstruction.
Anti-diarrheal medications
- An anti-diarrheal drug is any medication which provides symptomatic relief for diarrhea.
- Opiates slow intestinal transit time, but Loperamide and Diphenoxylate with Atropine are most commonly used, since they do not have the usual side effects associated with narcotic use.
Loperamide/ Imodium
- Category: Antidiarrheal – analog of Meperidine.
- MOA: Diminished peristalsis due to activation of opiate receptors in GI tract. Loperamide is an opioid receptor agonist and acts on the μ-opioid receptors in the myenteric plexus within the large intestines. It does not affect the central nervous system like other opioids.
Diminished activity of the myenteric plexus decreases the motility of the circular and longitudinal smooth muscles of the intestinal wall. This increases the amount of time substances stay in the intestine, allowing for more water to be absorbed out of the fecal matter.
• Indication: Acute diarrhea and the management of chronic diarrhea in patients with inflammatory bowel disease.
Loperamide/Imodium char, SE
Char: PO. Generally well tolerated. No inherent analgesic properties.
• Side effects: Dizziness, headache. Generally, not to be used in parasitic or bacterial infections accompanied by fever.
***Not to be used in severe colitis due to risk of toxic megacolon.
Diphenoxylate with Atropine/ Lomotil
- Category: Antidiarrheal
- MOA: Combination of morphine analog and acetylcholine inhibitor results in diminished peristalsis.
- Indication: Acute diarrhea
- Char: PO. Generally not indicated beyond 48 hours without consulting a physician. Although an analog of Meperidine, there are no inherent pain relieving effects.
Diphenoxylate with Atropine/ Lomotil SE
• Side effects: Dry mouth is quite common, urinary retention, abdominal pain, constipation, (atropine effects).
Not to be used in diarrhea due to bacterial or parasitic infections/ Fever.
*** Contraindicated in patients with severe colitis due to risk of toxic megacolon.

Other anti-diarrheal agents
• Bismuth subsalicylate (Pepto-Bismol)
• Bismuth subsalicylate (Kaopectate)*
• Opiates and synthetic opiates
* Please note that the original formulation of Kaopectate was kaolin clay (kaolinite) and pectin. The active ingredient of Kaopectate is now bismuth subsalicylate, the same active found in Pepto-Bismol.
Emesis
vomiting center in the medulla is activated by stimuli such as vertigo and the gag reflex.
- Two sites in the brain stem have key roles in the vomiting reflex pathway: the chemoreceptor trigger zone (CRTZ) and the vomiting center (VC), which coordinates the motor mechanisms involved in vomiting.
- Both the CRTZ and the VC have multiple receptors, including histamine, dopamine type 2 (DA2) and serotonin type 3 (5-HT3) and serotonin type 4 (5-HTP4).
Anti-emetics
- Different anti-emetic agents may be utilized depending on the severity of nausea or vomiting.
- Mild nausea and vomiting may respond to antihistamines.
- Moderate to severe N/V may require more potent agents that block the 5-HT3 receptor sites.
Meclizine/ Antivert
- Category: Antiemetic
- MOA: H1 Histamine blocker
- Indication: Mild to moderate nausea such as in motion sickness or vertigo.
- Char: PO. Sedating antihistamine
- Side effects: Drowsiness, dizziness, dry mouth, urinary retention.
Metoclopramide/ Reglan
- Category: Antiemetic/ pro-kinetic
- MOA: Dopamine 2 blocker and mixed serotonin 3 antagonist/serotonin 4 agonist
- Indication: Mild to moderate nausea, gastric stasis (i.e. after gastric surgery or diabetic gastroparesis. Also used in gastroesophageal reflux disease (GERD).
anti-emetic action of Metoclopramide is largely due to its antagonist activity at D2 receptors in the chemoreceptor trigger zone (CTZ). In more severe nausea and vomiting such as N/V associated with cancer chemotherapy, it has been superseded by the more effective 5-HT3 antagonists i.e. Ondansetron.
Metoclopramide/ Reglan car, SE
- Char: Metoclopramide increases peristalsis of the jejunum and duodenum, increases tone and amplitude of gastric contractions, and relaxes the pyloric sphincter tone.
- Side effects: Drowsiness, dizziness and headache. It should be used with caution in Parkinson’s disease since, as a dopamine antagonist, it may worsen symptoms.
Contraindicated in patients with suspected bowel obstruction.

Ondansetron/ Zofran
- Category: Antiemetic
- MOA: Blockade of serotonin (5HT3) receptor sites results in signifigant anti- nausea effect.
- Indication: Severe nausea
- Char: PO, IV. Effective agent for the severe nausea due to various chemotherapeutic agents. Given approximately 30 minutes or so prior to chemotherapeutic agent.
- Side effects: Dizziness, headache. Generally well tolerated.
Other antiemetic drugs
• Corticosteroids such as Decadron may also be used for chemotherapy induced nausea. The exact mechanism of action for the antiemetic effects of a corticosteroid is not known.
• Marijuana derivatives or cannabinoids such as dronabinol (Marinol) are effective for mild to moderate nausea but can cause vertigo, disorientation and dysphoria.

Emetic/ Syrup of Ipecac
- Category: Emetic
- MOA: Stimulation of medullary chemoreceptor trigger zone and local irritant of GI tract
- Indication: Induction of vomiting for drug overdose and certain poisonings.
- Char: PO. Effective orally, may produce emesis in 10 to 30 minutes. Give with large doses of water.
derived from the dried rhizome and roots of the Ipecacuanha plant,
Syrup of Ipecac SE
- Do not administer an emetic to any person with a diminished level of consciousness or to anyone who is unconscious.
- Do not use an emetic for caustic poisoning.
- Syrup of Ipecac is not generally given with charcoal, which will absorb the drug.
- Side effects: Abdominal muscle spasm (often lasting hours after stomach contents are emptied), dizziness and dehydration.
Gastritis
- Gastritis is inflammation of the gastric mucosa.
- Depending on the cause, gastritis may develop acutely or may persist chronically.
- There are multiple potential causes for gastritis including: bacterial infection (most often by H. pylori), aspirin and NSAID use, fungal infections (most often associated with immunodeficiency states), parasitic infections, viral infections, bile reflux, tobacco use, excessive alcohol consumption, certainconsumption, stress…