Pharmacology of GI Motility Drugs

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Questions and Answers

What is the primary mechanism of action for Rifaximin in treating traveler’s diarrhea?

Killing invasive strains of bacteria

Acting locally against noninvasive strains of Escherichia coli (correct)

Altering gastrointestinal pH levels

Stimulating peristalsis in the intestines

Which medication is a selective serotonin type 4 receptor agonist used for chronic constipation?

Alosetron

Tegaserod (correct)

Prucalopride (correct)

Lubiprostone

What is a potential adverse effect specifically associated with Alosetron?

Ischemic colitis (correct)

Nausea

Pancreatitis

Self-harm behaviors

Which of the following drugs is indicated for severe diarrhea-prominent IBS?

Alosetron Signup and view all the answers

Which drug is contraindicated in patients with a mechanical gastrointestinal obstruction?

All of the above Signup and view all the answers

What is a common cause associated with Irritable Bowel Syndrome (IBS)?

Stress and autonomic nervous system dysregulation Signup and view all the answers

Why is Prucalopride specifically prescribed for chronic constipation?

It stimulates gastrointestinal motility Signup and view all the answers

What is the recommended duration for using laxatives according to therapeutic guidelines?

Only on a short-term basis Signup and view all the answers

Which of the following is true about the action of Linaclotide?

It is a chloride channel activator Signup and view all the answers

What unique side effect may occur with the use of Prucalopride or Tegaserod?

New onset of depression Signup and view all the answers

What is the primary therapeutic action of stimulant laxatives?

They chemically irritate the lining of the GI tract. Signup and view all the answers

Which type of laxative is designed to enhance fecal bulk?

Bulk-forming laxatives Signup and view all the answers

What is a common adverse effect associated with osmotic laxatives?

Dehydration Signup and view all the answers

Which of the following drugs is classified as a bulk-forming laxative?

Methylcellulose Signup and view all the answers

Why should stimulant laxatives be used cautiously in certain patients?

They may cause dependency and overuse. Signup and view all the answers

What is the primary indication for using laxatives?

To relieve constipation Signup and view all the answers

Which laxative type can block the absorption of fats?

Chemical stimulants Signup and view all the answers

What condition contraindicates the use of osmotic laxatives like lactulose?

Intestinal obstruction Signup and view all the answers

Which symptom is commonly associated with the use of stimulant laxatives?

Abdominal cramping Signup and view all the answers

What should patients be advised to do when taking bulk-forming laxatives?

Take with plenty of water. Signup and view all the answers

Which adverse effect is specifically linked to the use of castor oil?

It can lead to malnutrition. Signup and view all the answers

What is a potential risk when using laxatives over a long period?

Decreased laxative effectiveness Signup and view all the answers

Which of the following laxative types works by increasing the osmotic pull of fluid into the GI tract?

Osmotic laxatives Signup and view all the answers

What adverse effect may occur due to too rapid administration of osmotic laxatives?

Dehydration Signup and view all the answers

Which medication is indicated for the treatment of chronic idiopathic constipation?

Lactitol (Pizensy) Signup and view all the answers

What is the primary benefit of lubricants when treating constipation?

Facilitating easier defecation without stimulating movement Signup and view all the answers

Which of the following lubricants can interfere with the absorption of fat-soluble vitamins?

Mineral Oil (Agoral) Signup and view all the answers

What is the major action of opioid agonists in relation to constipation?

They block the effects of opioids on the GI tract. Signup and view all the answers

Which gastrointestinal stimulant is known for increasing GI secretions and motility?

Metoclopramide (Reglan) Signup and view all the answers

What condition should contraindicate the use of opioid agonists?

Bowel obstruction Signup and view all the answers

Which drug specifically blocks chloride channels to reduce water loss during diarrhea?

Crofelemer (Mytesi) Signup and view all the answers

Which of the following medications is an opioid derivative used to relieve diarrhea?

Opium derivatives (Paregoric) Signup and view all the answers

What is a common adverse effect associated with the use of opioids for constipation?

Nausea Signup and view all the answers

What pharmacokinetic property is true for gastrointestinal stimulants?

Metabolized in the liver and excreted in feces. Signup and view all the answers

Which of the following side effects is most likely associated with the use of gastrointestinal stimulants?

Tardive dyskinesia Signup and view all the answers

What should be monitored in patients taking opioid agonists?

Opioid withdrawal symptoms Signup and view all the answers

What is a common therapeutic action of antidiarrheals?

Slowing the motility of the GI tract Signup and view all the answers

Which laxative is primarily a hyperosmolar agent?

Lactitol (Pizensy) Signup and view all the answers

What caution should be noted when using mineral oil?

It may cause staining and leakage. Signup and view all the answers

Study Notes

Actions of Drugs Used to Affect Motor Activity or Motility of the GI Tract

Speed up or improve movement of intestinal contents along the GI tract when movement becomes slow or sluggish to allow for proper excretion of wastes (constipation).
Increase the tone of the GI tract and stimulate motility throughout the system.
Decrease movement along the GI tract when rapid movement decreases the time for absorption of nutrients (diarrhea).

Laxatives

Indicated for short-term relief of constipation, to prevent straining, to evacuate bowel for diagnostic procedures, to remove ingested poisons, and as adjunct for anthelmintic activity.
Most available as OTC preparations
- Have potential for overuse, dependency

Kinds of Laxatives

Stimulants: chemically irritate the lining of the GI tract
Bulk-forming agents: cause fecal matter to increase in bulk
Osmotic: pull more solute and/or water into the GI tract
Lubricants: help intestinal contents stay softer, more slippery
Newer laxatives available for specific needs: alter sodium absorption or affect opioid receptors in the GI tract

Chemical Stimulants #1

Directly stimulate nerve plexus, causing increased movement and stimulation of local reflexes.
Drugs:
- Bisacodyl (Dulcolax)
- Castor oil (generic)
- Senna (Senokot)

Chemical Stimulants #2

Therapeutic actions:
- Begin working at the beginning of the small intestine
- Increase motility throughout the rest of the GI tract by stimulating the nerve plexus
- Castor oil blocks absorption of fats
Indications:
- Short-term treatment of constipation
Pharmacokinetics:
- Most of these agents are only minimally absorbed and exert their therapeutic effects directly in the GI tract

Chemical Stimulants #3

Contraindications:
- Allergy
- Acute abdominal disorders
- Castor oil: pregnancy
Caution:
- Heart block, CAD, debilitation
- Acute abdominal pain, nausea, or vomiting
- Pregnancy and lactation

Chemical Stimulants #4

Adverse effects:
- GI: diarrhea, abdominal cramping, nausea
- CNS: dizziness, headache, weakness
- Sweating, palpitations, flushing, fainting
- Cathartic dependence
- Castor oil: blocks absorption of fats (including fat-soluble vitamins) and may lead to malnutrition
Drug–drug interactions:
- Other prescribed medications

Bulk-Forming Laxatives #1

Cause fecal matter to increase in bulk.
Increase motility of the GI tract by increasing the size of fecal matter.
- Helps pull more fluid in intestinal contents
- Stimulates local stretch receptors and activates local activity
Drugs:
- Methylcellulose (Citrucel)
- Polycarbophil (FiberCon)
- Psyllium (Metamucil)

Bulk-Forming Laxatives #2

Therapeutic actions:
- Act in manner similar to dietary fiber
Indications:
- Treatment of constipation
- Decrease diarrhea in patients with diverticulosis or IBS
Pharmacokinetics:
- Directly effective within the GI tract; not generally absorbed systemically
- Can act rapidly

Bulk-Forming Laxatives #3

Contraindications:
- Allergy
- Acute abdominal disorders
- Acute infections
- Intestinal obstruction, perforation, rectal bleeding, or healing from acute abdominal surgery

Bulk-Forming Laxatives #4

Adverse effects:
- GI effects: diarrhea, abdominal cramping, nausea
- CNS effects: dizziness, headache, weakness
- Sweating, palpitations, flushing, fainting
- Advise patients to take with plenty of water
Drug–drug interactions:
- Other prescribed medications

Osmotic Laxatives #1

Have solutes that increase osmotic pull of fluid into GI tract.
Increase pressure in the GI tract and stimulate more intestinal motility.
Drugs:
- Magnesium sulfate (Epsom salts)
- Magnesium citrate (Citrate of Magnesia)
- Magnesium hydroxide (Milk of Magnesia)
- Lactulose (Constilac, Cholac)
- Lactitol (Pizensy)
- Polyethylene glycol (MiraLAX)
- Polyethylene glycol electrolyte solution (GoLYTELY)
- Sodium picosulfate with magnesium oxide and citric acid (Clenpiq)

Osmotic Laxatives #2

Therapeutic actions:
- Draw more water into the GI tract and stimulate increased GI motility
- Specific actions vary by drug
Indications:
- Treatment of constipation
- Other specific indications vary by drug
Pharmacokinetics:
- Rates of action vary based on formulation and route of administration

Osmotic Laxatives #3

Contraindications:
- Acute surgical abdomen
- Fecal impaction
- Intestinal obstruction
- Lactulose: appendicitis
Cautions:
- Lactulose: diabetes
- Magnesium: renal insufficiency
- Polyethylene glycol: history of seizures

Osmotic Laxatives #4

Adverse effects:
- GI effects: diarrhea, abdominal cramping, abdominal bloating, nausea
- Dehydration: dry mouth, dizziness, light-headedness
- CNS effects: dizziness, headache, weakness
- Sweating, palpitations, flushing, fainting
- Suppositories: rectal irritation
Drug–drug interactions:
- Other medications
- Magnesium salts: neuromuscular junction blockers

Lubricants #1

Make defecation easier without stimulating movement of the GI tract.
Benefit patients with hemorrhoids, who have had recent rectal surgery, or who could be harmed by straining.
Choice depends on condition, speed of relief needed, adverse effects.
Drugs:
- Docusate (Colace)
- Glycerin (Sani-Supp)
- Mineral Oil (Agoral)

Lubricants #2

Therapeutic actions:
- Docusate: Detergent action on surface of intestinal bolus
- Glycerin: Hyperosmolar laxative gently evacuates rectum without systemic effects higher in GI tract
- Mineral oil: Forms slippery coating on contents of intestinal tract
Indications:
- Short-term treatment of constipation

Lubricants #3

Pharmacokinetics:
- Not absorbed systemically
- Excreted in feces
Contraindications:
- Allergy
Cautions:
- Abdominal disorders
- Pregnancy and lactation

Lubricants #4

Adverse effects:
- GI effects: diarrhea, abdominal cramping, nausea
- Mineral oil: leakage and staining
- CNS effects: dizziness, headache, weakness
- Sweating, palpitations, flushing, fainting (less likely with lubricant laxatives than with others)
Drug–drug interactions:
- Frequent use of mineral oil can interfere with the absorption of the fat-soluble vitamins A, D, E, and K.

Opioid Agonists #1

May be used to relieve constipation in specific situations.
Drugs:
- Alvimopan (Entereg)
- Methylnaltrexone bromide (Relistor)
- Naloxegol (Movantik)
- Naldemedine (Symproic)

Opioid Agonists #2

Therapeutic actions:
- Block effects of opioids on the GI tract by selectively binding to peripheral opioid receptors
  - Can help maintain normal motility and secretions while patient is on opioid treatment for pain
Indications:
- Treatment of opioid-induced constipation
- Alvimopan: Hasten time to gastrointestinal recovery following surgeries that include partial bowel resection with primary anastomosis

Opioid Agonists #3

Pharmacokinetics:
- All but alvimopan: metabolized in the liver
- Alvimopan: mostly changed to metabolites in the GI tract
- Eliminated partially by the kidneys and partially in feces
Contraindications:
- Bowel obstruction
- More than 15 doses of alvimopan
Cautions:
- Hepatic or renal impairment
- Pregnancy and lactation

Opioid Agonists #4

Adverse effects:
- Abdominal pain, diarrhea, nausea, vomiting, dizziness, flatulence, headache
- Monitor patients for opioid withdrawal symptoms
- Monitor for GI perforation if abdominal pain is severe
Drug–drug interactions:
- Other opioid antagonists
- Naloxegol and naldemedine with CYP3A inducers or CYP3A4 inhibitors

Gastrointestinal Stimulant #1

More generalized GI stimulation results in an overall increase in GI activity and secretions.
Stimulate parasympathetic activity or make GI tissues more sensitive to parasympathetic activity.
Metoclopramide (Reglan)

Gastrointestinal Stimulant #2

Therapeutic actions:
- Stimulates parasympathetic activity within the GI tract
  - Increases GI secretions and motility
- Blocks dopamine receptors and makes GI cells more sensitive to acetylcholine
  - Leads to increased GI activity and rapid movement of food through the upper GI tract
Indications:
- When rapid movement of GI contents is desirable

Gastrointestinal Stimulant #3

Pharmacokinetics:
- Rapidly absorbed
- Metabolized in the liver, excreted in feces and urine
- Crosses placenta and enters human milk
Contraindications:
- Allergy
- GI obstruction or perforation
Cautions:
- Pregnancy and lactation
- History of tardive dyskinesia, seizures, or depression

Gastrointestinal Stimulant #4

Adverse effects:
- Nausea, vomiting, diarrhea, intestinal spasms, cramping
- Declining blood pressure and heart rate, weakness, and fatigue
- Boxed warning: tardive dyskinesia
Drug–drug interactions:
- Alcohol or other CNS sedative drugs
- Antipsychotic medications
- MAOIs
- Strong CYP2D6 inhibitors

Antidiarrheals #1

Block stimulation of GI tract for symptomatic relief from diarrhea.
Drugs:
- Bismuth subsalicylate (Pepto-Bismol)
- Crofelemer (Mytesi)
- Loperamide (Imodium A-D)
- Opium derivatives (Paregoric)
- Some anticholinergic medications (Chapter 33)
- Several available in combination

Antidiarrheals #2

Therapeutic actions:
- Slow motility of the GI tract
  - Bismuth subsalicylate: Direct action on the lining of the GI tract
  - Loperamide: Direct action on muscles of the GI tract
  - Opium derivatives: Action on CNS centers to cause GI spasm and slowing
  - Crofelemer: Blocks specific chloride channels leading to less water loss as diarrhea

Antidiarrheals #3

Indications:
- Relief of symptoms of acute and chronic diarrhea
- Reduction of volume of discharge from ileostomies
- Prevention and treatment of traveler’s diarrhea
- Bismuth subsalicylate: Diarrhea and GI symptoms associated with dietary excess, some viral infections
- Crofelemer: Symptomatic relief of noninfectious diarrhea in adult patients on HIV/AIDS antiretrovirals
Pharmacokinetics:
- Vary depending on agent

Antidiarrheals #4

Contraindications:
- Allergy
Cautions:
- Pregnancy and lactation
- History of GI obstruction
- Acute abdominal conditions
- Diarrhea due to poisonings
- Hepatic impairment

Antidiarrheals #5

Adverse effects:
- Related to effects on the GI tract: constipation, distention, abdominal discomfort, nausea, vomiting, dry mouth, toxic megacolon
- Other effects: fatigue, weakness, dizziness, skin rash
- Opium derivatives: light-headedness, sedation, euphoria, hallucinations, respirator depression
Drug–drug interactions:
- Vary depending on agent

IBS and Chronic Constipation Drugs #1

IBS affects three times as many females as males.
Reportedly accounts for half of referrals to GI specialists.
Characterized by abdominal distress, bouts of diarrhea or constipation, bloating, nausea, flatulence, headache, fatigue, depression, anxiety.
Underlying causes may be stress and/or dysregulation of the autonomic nervous system.
Drugs to treat IBS:
- Alosetron (Lotronex)
- Eluxadoline (Viberzi)
- Linaclotide (Linzess)
- Lubiprostone (Amitiza)
- Plecanatide (Trulance)
- Tegaserod (Zelnorm)
- Hyoscyamine (Chapter 33)
Drug to treat chronic constipation: Prucalopride (Motegrity)

IBS and Chronic Constipation Drugs #2

Therapeutic actions and indications:
- Alosetron
  - Serotonin 5-HT antagonist
  - Severe diarrhea-prominent IBS
- Eluxadoline
  - Mu-opioid receptor agonist
  - Adults with IBS with diarrhea
- Lubiprostone
  - Locally acting chloride channel activator
  - Chronic, idiopathic constipation, opioid-induced constipation, IBS with constipation in adult females

IBS and Chronic Constipation Drugs #3

Therapeutic actions and indications (cont.)
- Prucalopride and tegaserod
  - Selective serotonin type 4 receptor agonists
  - Chronic constipation
  - Tegaserod: Females younger than 65 who suffer from constipation due to IBS
- Linaclotide and plecanatide
  - Guanylate cyclase-C agonists
  - Chronic constipation and constipation type IBS

IBS and Chronic Constipation Drugs #4

Pharmacokinetics:
- Most are absorbed quickly
- Location and extent of metabolism varies
Contraindications:
- Allergy
- Mechanical gastrointestinal obstruction
- Other contraindications vary by agent
Cautions:
- Pregnancy and lactation

IBS and Chronic Constipation Drugs #5

Adverse effects:
- GI symptoms: nausea, abdominal pain, diarrhea, constipation
- Alosetron: ischemic colitis
- Eluxadoline: pancreatitis
- Prucalopride and tegaserod: new onset of depression and self-harm behaviors
Drug–drug interactions:
- Alosetron or eluxadoline: medications that slow GI motility
- Alosetron: CYP1A2 inhibitors; fluvoxamine

Why should laxatives be taken only on a short-term basis?

Laxative use can lead to dependence, making the bowels less likely to naturally function correctly.
Laxative overuse can damage the bowels.
Laxative overuse can lead to dehydration.
Laxative overuse can lead to electrolyte imbalances
Laxative overuse can make it more difficult to treat certain gastrointestinal diseases.

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Description

This quiz explores the actions and classifications of drugs that affect motor activity in the gastrointestinal tract. It covers laxatives, their uses, and the different types available, along with their mechanisms of action. Test your knowledge on how these medications work to manage conditions like constipation and diarrhea.