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DRUGS AFFECTING THE
LOWER GASTROINTESTINAL
TRACT
NURSING CONCEPT:
ELIMINATION
 Control
(continence)
 Requires cognition & neuromuscular
integrity
 Retention
 Obstructions, inflammation, ineffective
neuromuscular activation
 Discomfort
 Infection/inflammation; hard stools,
hemorrhoids
PHYSIOLOGY OF THE LARGE INTESTINES
http://www.youtube.com/watch?v=18M96_p7jSQ
PHYSIOLOGY OF THE LARGE INTESTINE
 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
 Large
moves the contents down
amounts of mucus are secreted by
goblet cells in the epithelial layer of the
intestine.
PATHOPHYSIOLOGY

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.
ANTIFLATULENTS
 Antiflatulents
decrease gas production.
Prototype drug: simethicone (Mylicon)
SIMETHICONE: PLANNING AND INTERVENTIONS
 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.
SIMETHICONE: CORE DRUG KNOWLEDGE
 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

SIMETHICONE: CORE DRUG KNOWLEDGE (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.
ANTIDIARRHEALS
 Antidiarrheals
slow intestinal motility,
allowing time for fluid reabsorption and
better stool formation.
Prototype drug: diphenoxylate HCl
with atropine sulfate (Lomotil)
DIPHENOXYLATE: CORE DRUG KNOWLEDGE
 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.

DIPHENOXYLATE: CORE DRUG KNOWLEDGE (CONT.)
 Contraindications
and precautions
Hypersensitivity
 Adverse effects
 Drowsiness and dizziness
 Drug interactions
 Some antidepressants, alcohol, barbiturates,
and tranquilizers (CNS Sedatives)

ANTIDIARRHEALS
 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
ANTIDIARRHEALS:
BISMUTH 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
CONSTIPATION
A very common complaint in health care
 How constipation happens:
http://www.youtube.com/watch?v=cdijh32NiLs


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
TREATMENT FOR CONSTIPATION
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

LAXATIVES
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)
LAXATIVES
TYPE
PHARMACOTHERAPEUTICS
• Treat constipation
• Decrease diarrhea in IBS
• Bulk forming laxative
• Softens fecal mass by increasing • Control stool for person with a
colostomy
bulk in the diet
• Promote regular BMs
Psyllium (Metamucil)
Docusate (Colace)
• Lower surface tension of the
feces to allow penetration of
water
Bisacodyl (Dulcolax)
• Stimulant laxative works by
stimulating intestinal
peristalsis
• Relieve constipation or painful
elimination
• Prevent straining and reduce
risk of fecal impaction
• Prepare client for surgery or
colon tests
• Treat severe constipation
• Short-term use
MAGNESIUM HYDROXIDE: CORE DRUG KNOWLEDGE
 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

MAGNESIUM HYDROXIDE: PLANNING AND
INTERVENTIONS
 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.
EMOLLIENTS (STOOL SOFTENERS)
 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
PROKINETIC AGENTS
 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)
METOCLOPRAMIDE: PLANNING AND INTERVENTIONS
 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.
METOCLOPRAMIDE: PLANNING AND INTERVENTIONS
 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!
DRUGS USED TO TREAT IRRITABLE BOWEL
SYNDROME (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:
http://www.youtube.com/watch?v=b3pLHpnvKi8
Blockade of serotonin receptor subtype 3 (5-HT3)
decreases the diarrhea associated with IBS.
Prototype drug:
alosetron (Lotronex)
DRUGS USED TO TREAT IRRITABLE BOWEL
SYNDROME (IBS) WITH CONSTIPATION
 Increases
fluid secretion in the intestine to
promote intestinal motility
Prototype drug:
lubiprostone
(Amitiza)
ALOSETRON: CORE DRUG KNOWLEDGE
 Pharmacotherapeutics
Treatment of IBS
 Pharmacokinetics
 Administered: oral. Metabolism: liver.
Absorption: Excreted: urine and feces.
 Pharmacodynamics
 Blocks the 5-HT3 receptor
 Alters visceral sensation, decreasing
abdominal discomfort and pain

ALOSETRON: CORE DRUG KNOWLEDGE (CONT.)
 Contraindications
and precautions
 History of chronic constipation
 Adverse effects
 Constipation
 Drug interactions
 No important drug interactions with
alosetron have been identified.
DRUGS USED TO TREAT INFLAMMATORY BOWEL
DISEASE (IBD)


Drug therapy cannot cure IBD.
The drug groups used to treat IBD include the 5aminosalicylic acid (5-ASA) preparations,
corticosteroids, and drugs that suppress the immune
system.
5-ASA preparations

Aminosalicylates (5-ASA) are the antiinflammatory drugs most
prescribed for IBD.
Prototype drug:
sulfasalazine (Azulfidine)