D RUGS A FFECTING THE L OWER G ASTROINTESTINAL T RACT

N URSING C ONCEPT : E LIMINATION Control (continence) Requires cognition & neuromuscular integrity Retention Obstructions, inflammation, ineffective neuromuscular activation Discomfort Infection/inflammation; hard stools, hemorrhoids

P HYSIOLOGY OF THE L ARGE I NTESTINES

P HYSIOLOGY OF THE L ARGE I NTESTINE Large intestine is about 5 ft. long & 2.5 inches in across Large intestine is composed of the cecum, colon, rectum, and anal canal. The contents from the small intestine enter the cecum through the ileocecal valve. Peristalsis moves the contents down Large amounts of mucus are secreted by goblet cells in the epithelial layer of the intestine.

P ATHOPHYSIOLOGY Flatus (gas) Is a normal by-product of digestion. Diarrhea Is the frequent passage of loose or liquid stools. Constipation Is infrequent or incomplete passage of hard stools resulting from a decrease in peristaltic activity. Irritable bowel syndrome (IBS) Is a common disorder of the intestines characterized by altered bowel habits and pain. Inflammatory bowel disease (IBD) Is a general term that includes both ulcerative colitis and Crohn’s disease.

A NTIFLATULENTS Antiflatulents decrease gas production. Prototype drug: simethicone (Mylicon)

S IMETHICONE : P LANNING AND I NTERVENTIONS Maximizing therapeutic effects Simethicone should be given after meals and at bedtime to increase its effectiveness. The suspension form of the drug must be shaken to ensure that the active ingredients are well dispersed.

S IMETHICONE : C ORE D RUG K NOWLEDGE Pharmacotherapeutics Relieves the discomfort of excess gas Pharmacokinetics Not absorbed from GI tract. Excreted: feces. Pharmacodynamics Defoaming action that alters the surface tension of gas bubbles

S IMETHICONE : C ORE D RUG K NOWLEDGE ( CONT.) Contraindications and precautions Simethicone has no contraindications or precautions. Adverse effects No substantial adverse reactions Drug interactions No drug interactions with simethicone are known.

A NTIDIARRHEALS Antidiarrheals slow intestinal motility, allowing time for fluid reabsorption and better stool formation. Prototype drug: diphenoxylate HCl with atropine sulfate (Lomotil)

D IPHENOXYLATE : C ORE D RUG K NOWLEDGE Pharmacotherapeutics Adjunct in treating diarrhea Pharmacokinetics Administered: oral. Metabolism: liver. Excreted: urine and feces. Pharmacodynamics - CHOLINERGIC Acts on the smooth muscle of the intestine to slow intestinal motility and prolong intestinal transit time, allowing for the reabsorption of fluid.

D IPHENOXYLATE : C ORE D RUG K NOWLEDGE ( CONT.) Contraindications and precautions Hypersensitivity Adverse effects Drowsiness and dizziness Drug interactions Some antidepressants, alcohol, barbiturates, and tranquilizers (CNS Sedatives)

A NTIDIARRHEALS Treats diarrhea, heartburn, nausea, and upset stomach. This medicine contains a salicylate and is related to aspirin. Used in combination with antibiotics when treating H. pylori infection Prototype: Bismuth salicylate

A NTIDIARRHEALS : B ISMUTH SALICYLATE o Adverse Effects o Ringing or buzzing in your ear(s) o Do not give to children with symptoms of viral illness due to risk for Reye’s Syndrome

C ONSTIPATION A very common complaint in health care How constipation happens: Causes: Insufficient fluid (water) intake Poor dietary habits Lack of exercise Slowed peristalsis Fecal impaction Bowel obstruction Chronic laxative use Neurologic disorders (paraplegia) Ignoring the urge to defecate Drug side effects

T REATMENT FOR C ONSTIPATION High fiber diet Laxatives – promote a soft stool 4 types: Osmotics (saline) Stimulants Bulk-forming e.g. Psyllium (Metamucil) Emollients (stool softeners) Cathartics – cause a soft to watery stool with some cramping Purgatives – result in a harsh catharsis with cramping

L AXATIVES Drugs used to treat constipation are referred to as laxatives. Laxatives are drugs that act directly on the intestine to promote peristalsis and evacuation of the bowel. Laxatives are classified as saline, hyperosmotic, stimulant, and bulk forming. Saline laxatives Attract or retain water in the intestinal lumen, resulting in an increased intraluminal pressure that stimulates peristalsis. Prototype drug: magnesium hydroxide (Milk of Magnesia)

L AXATIVES TYPEPHARMACOTHERAPEUTICS Psyllium (Metamucil) Bulk forming laxative Softens fecal mass by increasing bulk in the diet Treat constipation Decrease diarrhea in IBS Control stool for person with a colostomy Promote regular BMs Docusate (Colace) Lower surface tension of the feces to allow penetration of water Relieve constipation or painful elimination Prevent straining and reduce risk of fecal impaction Bisacodyl (Dulcolax) Stimulant laxative works by stimulating intestinal peristalsis Prepare client for surgery or colon tests Treat severe constipation Short-term use

M AGNESIUM H YDROXIDE : C ORE D RUG K NOWLEDGE Pharmacotherapeutics Constipation and prepare the bowel for surgery Pharmacokinetics Local effect on GI tract. Duration: 2 to 6 hours. Pharmacodynamics Attracting and retaining water in the intestinal lumen

M AGNESIUM H YDROXIDE : P LANNING AND I NTERVENTIONS Maximizing therapeutic effects The patient should follow with a full glass of water to prevent dehydration and to promote a more rapid effect. Minimizing adverse effects Limit to short-term use. At least 2 hours should pass between administration of magnesium hydroxide and drugs that are known to interact with it.

E MOLLIENTS (S TOOL S OFTENERS ) Decrease straining during defecation Lubricants Mineral Oil Side effects: cramping, nausea, vomiting, diarrhea Stool Softeners Prototype: Docusate sodium (Colace) Side effects: cramping, nausea, vomiting, diarrhea – no adverse effects

P ROKINETIC A GENTS Prokinetic agents increase the effect of acetylcholine in the GI system. Acetylcholine is responsible for normal GI function. Prokinetic agents increase peristalsis and gastric emptying. Prototype drug: metoclopramide (Reglan)

M ETOCLOPRAMIDE : P LANNING AND I NTERVENTIONS Maximizing therapeutic effects Give oral doses 30 minutes before each meal. Do not administer metoclopramide concurrently with anticholinergic drugs. Minimizing adverse effects Monitor for evidence of depression. Withhold the dose and notify the prescriber if Parkinson-like symptoms occur.

M ETOCLOPRAMIDE : P LANNING AND I NTERVENTIONS Maximizing therapeutic effects Give oral doses 30 minutes before each meal. Do not administer metoclopramide concurrently with anticholinergic drugs. Minimizing adverse effects Monitor for evidence of depression. Withhold the dose and notify the prescriber if involuntary muscle movements occur (related to CNS acetylcholine activity) – can become irreversible!

D RUGS U SED TO T REAT I RRITABLE B OWEL S YNDROME (IBS) WITH DIARRHEA Serotonin receptors in the bowel play a role in bowel motility. Drugs that work at these receptors can alter symptoms of Irritable Bowel or Crohn’s Disease For more information on these disorders see 10 minute video: Blockade of serotonin receptor subtype 3 (5-HT 3 ) decreases the diarrhea associated with IBS. Prototype drug: alosetron (Lotronex)

D RUGS U SED TO T REAT I RRITABLE B OWEL S YNDROME (IBS) WITH CONSTIPATION Increases fluid secretion in the intestine to promote intestinal motility Prototype drug: lubiprostone (Amitiza)

A LOSETRON : C ORE D RUG K NOWLEDGE Pharmacotherapeutics Treatment of IBS Pharmacokinetics Administered: oral. Metabolism: liver. Absorption: Excreted: urine and feces. Pharmacodynamics Blocks the 5-HT 3 receptor Alters visceral sensation, decreasing abdominal discomfort and pain

A LOSETRON : C ORE D RUG K NOWLEDGE ( CONT.) Contraindications and precautions History of chronic constipation Adverse effects Constipation Drug interactions No important drug interactions with alosetron have been identified.

D RUGS U SED TO T REAT I NFLAMMATORY B OWEL D ISEASE (IBD) Drug therapy cannot cure IBD. The drug groups used to treat IBD include the 5- aminosalicylic acid (5-ASA) preparations, corticosteroids, and drugs that suppress the immune system. 5-ASA preparations Aminosalicylates (5-ASA) are the anti- inflammatory drugs most prescribed for IBD. Prototype drug: sulfasalazine (Azulfidine)