PHARMAC
OLOGY
MODULE 6
TOPIC
Drugs Acting on the Gastrointestinal System
1. Discuss the indications, pharmacokinetics. Side/adverse effects, and
nursing management of agents affecting the upper gastrointestinal tract:
a. Antacids (Gastric Acid Neutralizers) - page 729 Abrams
● Protype: Mylanta pg 20
● Indications: peptic ulcers, stress ulcers gastritis, peptic esophagitis, gastric
hyperacidity, heartburn, hiatal hernia, prophylaxis, GERD
● Pharmacokinetics: minimally absorbed in GI tract, rapid onset (20-60 min),
excreted in urine. Reacts with hydrochloric acid in stomach to produce
neutral, less acidic, or poorly absorbed salts and to raise the pH of gastric
secretions. Inhibits conversion of pepsinogen to pepsin.
● AE: constipation, diarrhea, hypermagnesemia, neuromuscular effects
(older adults), hypophosphatemia, osteomalacia
● Nursing Management: 1. Shake well (chew tabs - swallow with water) 2.
*Administer other drugs 1 hr before or 2 hours after antacid 3. Monitor bowel
function > fluid, fiber 4. Avoid sodium containing if HTN, cardiac, renal disease
● Education: 1. Eat slowly <caffeine and acidic food <smoking 2. Remain upright
after eating. 3. Eat small, frequent meals. 4. Do not use self-prescribed more than
2 weeks. 5. Do not exceed dosage on label.
b. Antisecretory drugs H2-Receptor Antagonists/Proton Pump
Inhibitor/Prostaglandins)
● Prototype: Cimetidine (Tagamet) - H2 Receptor Antagonist pg6
● Indications: prevent and treat PUD, GERD, esophagitis, GI bleeding due to
acute stress ulcers, and Zollinger-Ellison syndrome. OTC preparations for
treatment of heartburn.
● Pharmacokinetics: Metabolism takes place in liver, excretion of the unchanged
oral dose occurs unchanged in the urine within 24 hours, some excretion in bile,
elimination in feces. Inhibits action of histamine at H2 receptors in stomach,
decreasing acidity and pepsin content of gastric juices. (competitive blockers of
histamine at H2 receptor sites)
● AE: A lot of drug interactions. Diarrhea, dizziness, drowsiness, headache,
confusion, gynecomastia, impotence, <libido, <sperm count, Rare: confusion,
hallucinations, lethargy, restlessness, seizure. AE are likely with prolonged use of
high doses, increase with age, and with impaired renal or hepatic function.
● Nursing Management: 1. Assess for pain. 2. Monitor CBC, renal, hepatic
function. 3. Maintenance therapy at bedtime (HS). 4. Avoid late evening meals.
5. Give with meals; HS dose not with meals. 6. Separate with antacids by 1 hour
IV
, slowly. 7. Avoid alcohol, caffeine, high-fat food, large meals. 8.
Smoking cessation 4-6 week therapy
● Prototype: Omeprazole (Prilosec) - Proton Pump Inhibitor
● Indications: hypersecretory disorders, duodenal ulcer, erosive
esophagitis (GERD), PUD, gastric ulcers, Zollinger-Ellison syndrome.
● Pharmacokinetics: Block final stage of acid production. More popular than
H2RAs because they are more effective in the short-term.
● AE: Minimal for long and short term use.N/V/D, abdominal pain, constipation,
dizziness, and headache. *High dose or long-term use of PPIs carry a possible
increased risk of bone fractures. URI, cough, rash, back pain, muscle pain, Rare:
anemia, thrombocytopenia, eosinopenia, leukocytosis
● Nursing Management: Caution with elderly and young, 1. swallow whole 2. take
before meals 3. note date therapy 4. baseline GI symptoms
● 30min before food, prophylactic for stress surgery, bone density, C-diff longterm
● Prototype: *Misoprostol (Cytotec) - Prostaglandins (p 738 Abrams)
● Indications: for patients at high risk for GI bleeding and ulceration, such as those
taking high doses of NSAIDs for arthritis and older adults to protect gastric
mucosa from NSAID-induced erosion and ulceration.
● Pharmacokinetics: rapidly absorbed, excreted in urine, inhibits gastric acid
secretion, mucosal protective (suppress gastric acid secretion by inhibition of
H+/K+ATPase)
● AE: N/V/*D, *abdominal pain, dyspepsia, flatulence, headache, constipation,
toxicity: sedation, tremor, convulsions, dyspnea, abdominal pain, diarrhea,
fever, palpitations, hypotension, bradycardia
● Drug interactions: antacids
● Nursing Management: 1. Obtain serum pregnancy test before initiation
(Pregnancy X Hypersensitivity - BBW) 2. Initiate drug therapy on 2-3 day of next
period. 3. Provide verbal and written instructions to females of abortifacient
properties. 4. Assess for adequate contraception. 5. DISCONTINUE immediately
if pregnancy suspected. 6. Do not share drugs with others. 7. Report diarrhea > 1
week.
c. Antiemetic drugs (Phenothiazines & Serotonin Receptor Antagonist & Substance P)
● Protype: Promethazine (Phenothiazines)
● Indications: CNS depressants used for many reasons - also prevention and
treatment of N/V r/t surgery, anesthesia, migraines, chemotherapy, and
motion sickness (block dopamine from receptor sites in the brain and CTZ.)
● Pharmacokinetics: Rapidly absorbed oral administration, metabolism in
liver, excretion in urine.
● AE: blurred vision, urinary retention, dry mouth, photosensitivity, drowsiness,
and confusion
, ● Nursing Mangement: BBW: fatal in children <2 yrs because respiratory
depression, do not administer SQ(BBW)- IM preferred, use lowest
effective dosage, do not take with other respiratory depressant effects
concurrently.
● Prototype: Ondansetron (Zofran) (Serotonin Receptor Antagonist) pg.25
● Indications: prevent and treat N/emesis with chemotherapy,
radiation, perioperative
● Pharmacokinetics: Well absorbed in GI tract, oral onset 30-60 min. IV form
onset and peak immediately. Bioavailability slightly increased by presence of
food but unaffected by antacids.
● AE: diarrhea, constipation, headache, dizziness, rash, transient elevations in
AST/ALT, pain at injection site, Rare: bronchospasm, tachycardia, chest
pain, hypokalemia, ECG changes, tonic clonic seizures
● Nursing Management: Monitor bowel function and liver enzymes
● Prototype: aprepitant (Emend) - Substance P
● Indications: acute chemotherapy induced N/V, prevention of postoperative N/V
● Pharmacokinetics: absorbed orally, peak levels after 4 hours of administration,
highly protein bound, metabolized in the liver, excreted through urine and
feces
● AE: fatigue, weakness, dizziness, abnormal heart rhythm, headache, hiccups,
infusion site pain with IV administration. Has the potential for multiple drug
interactions.
● Nursing Management: Take medication as prescribed before the onset of N/V.
General Nursing Management for Antiemetics:
● Use measures to prevent or minimize N/V
● Assist patients to identify situations that cause or aggravate N/V
● Avoid exposure to stimuli when feasible (ex: excessive ingestion of food, alcohol, etc)
● Administer analgesics before painful diagnostic tests and dressing changes or other
therapeutic measures may be helpful, as pain may cause N/V
● Minimize activity during acute episodes of N/V - lying down and resting quietly are
often helpful
2. Describe the major laxative classifications based on the mechanism of
action, indications, side/adverse effects, and nursing management:
a. Stimulant
● Protype: Bisacodyl (Dulcolax)
● Mechanism of action: irritate GI mucosa, pulls water into bowel
● Pharmacokinetics: poorly absorbed in small intestine following oral
administration or in large intestine following rectal admin. Metabolized in
liver, primarily excreted in feces, some in urine. Half life: 16 hours
● Indication: relief of constipation, prior to surgery and medical exams,
neurogenic bowel dysfunction
, ● AE: abdominal pain, cramping, N/D, weakness
● Nursing Management: Take on empty stomach of at bedtime, swallow whole
(do not chew), do not take within an hour after ingesting milk or gastric antacids
or while receiving H2 receptor blocker therapy (this prevents abdominal
cramping and vomiting associated with premature tablet dissolution and gastric
irritation)
● Contraindicated in patients with undiagnosed abdominal pain, fecal
impaction, intestinal obstruction
b. Bulk-forming
● Protype: *Psyllium (Metamucil)
● Mechanism of action: acts within 12-24 hours, unabsorbed by body, absorbs
excess water to stimulate BM; adds bulk/size to fecal mass - pulls water into
the intestinal lumen.
● Indications: Constipation/diarrhea, bowel irregularity, lower cholesterol
(when combined with a diet low in cholesterol and saturated fat)
● AE: flatulence (severe), bloating, rare bowel obstruction
● Nursing Management: Can delay or reduce absorption of certain medications
(digoxin, carbamazepine, lithium, antidepressants, warfarin) - take 1 hour before
or 2-4 hours after taking other medications; take with 8 oz water, maintain
adequate intake of fluids (this will help improve bowel regularity)
c. Lubricant
● Protype: Mineral oil
● Mechanism of action: lubricates the fecal mass and slow colonic absorption of
water from the fecal mass (exact MOA is unknown). Effects usually occur within
6-8 hours.
● Indication: Most useful as a retention enema to soften hard, dry feces and aid
in their removal
● AE: Not recommended for long-term use - many AE: decreased absorption of fat-
soluble vitamins (A, D, E, and K) and some drugs, lipid pneumonia if aspirated
into the lungs
● Nursing Management: Do not use regularly
d. Miscellaneous
● Drug: Docusate Sodium (Colace) - Surfactant Laxative (stool softener)
● Mechanism of action: decrease the surface tension of the fecal mass to allow
water and fat to penetrate into the stool, making it softer and easier to expel
(have little true laxative effect)
● Indication: stool softener for constipation - main value is to prevent straining
while expelling stool
● AE: throat irritation, N, rash, facilitates transport of other substances, chronic
active liver disease
● Nursing Management: take daily, act within 1-3 days
● Drug Interactions (absorption): digoxin, quinidine, mineral oil, salicylates
OLOGY
MODULE 6
TOPIC
Drugs Acting on the Gastrointestinal System
1. Discuss the indications, pharmacokinetics. Side/adverse effects, and
nursing management of agents affecting the upper gastrointestinal tract:
a. Antacids (Gastric Acid Neutralizers) - page 729 Abrams
● Protype: Mylanta pg 20
● Indications: peptic ulcers, stress ulcers gastritis, peptic esophagitis, gastric
hyperacidity, heartburn, hiatal hernia, prophylaxis, GERD
● Pharmacokinetics: minimally absorbed in GI tract, rapid onset (20-60 min),
excreted in urine. Reacts with hydrochloric acid in stomach to produce
neutral, less acidic, or poorly absorbed salts and to raise the pH of gastric
secretions. Inhibits conversion of pepsinogen to pepsin.
● AE: constipation, diarrhea, hypermagnesemia, neuromuscular effects
(older adults), hypophosphatemia, osteomalacia
● Nursing Management: 1. Shake well (chew tabs - swallow with water) 2.
*Administer other drugs 1 hr before or 2 hours after antacid 3. Monitor bowel
function > fluid, fiber 4. Avoid sodium containing if HTN, cardiac, renal disease
● Education: 1. Eat slowly <caffeine and acidic food <smoking 2. Remain upright
after eating. 3. Eat small, frequent meals. 4. Do not use self-prescribed more than
2 weeks. 5. Do not exceed dosage on label.
b. Antisecretory drugs H2-Receptor Antagonists/Proton Pump
Inhibitor/Prostaglandins)
● Prototype: Cimetidine (Tagamet) - H2 Receptor Antagonist pg6
● Indications: prevent and treat PUD, GERD, esophagitis, GI bleeding due to
acute stress ulcers, and Zollinger-Ellison syndrome. OTC preparations for
treatment of heartburn.
● Pharmacokinetics: Metabolism takes place in liver, excretion of the unchanged
oral dose occurs unchanged in the urine within 24 hours, some excretion in bile,
elimination in feces. Inhibits action of histamine at H2 receptors in stomach,
decreasing acidity and pepsin content of gastric juices. (competitive blockers of
histamine at H2 receptor sites)
● AE: A lot of drug interactions. Diarrhea, dizziness, drowsiness, headache,
confusion, gynecomastia, impotence, <libido, <sperm count, Rare: confusion,
hallucinations, lethargy, restlessness, seizure. AE are likely with prolonged use of
high doses, increase with age, and with impaired renal or hepatic function.
● Nursing Management: 1. Assess for pain. 2. Monitor CBC, renal, hepatic
function. 3. Maintenance therapy at bedtime (HS). 4. Avoid late evening meals.
5. Give with meals; HS dose not with meals. 6. Separate with antacids by 1 hour
IV
, slowly. 7. Avoid alcohol, caffeine, high-fat food, large meals. 8.
Smoking cessation 4-6 week therapy
● Prototype: Omeprazole (Prilosec) - Proton Pump Inhibitor
● Indications: hypersecretory disorders, duodenal ulcer, erosive
esophagitis (GERD), PUD, gastric ulcers, Zollinger-Ellison syndrome.
● Pharmacokinetics: Block final stage of acid production. More popular than
H2RAs because they are more effective in the short-term.
● AE: Minimal for long and short term use.N/V/D, abdominal pain, constipation,
dizziness, and headache. *High dose or long-term use of PPIs carry a possible
increased risk of bone fractures. URI, cough, rash, back pain, muscle pain, Rare:
anemia, thrombocytopenia, eosinopenia, leukocytosis
● Nursing Management: Caution with elderly and young, 1. swallow whole 2. take
before meals 3. note date therapy 4. baseline GI symptoms
● 30min before food, prophylactic for stress surgery, bone density, C-diff longterm
● Prototype: *Misoprostol (Cytotec) - Prostaglandins (p 738 Abrams)
● Indications: for patients at high risk for GI bleeding and ulceration, such as those
taking high doses of NSAIDs for arthritis and older adults to protect gastric
mucosa from NSAID-induced erosion and ulceration.
● Pharmacokinetics: rapidly absorbed, excreted in urine, inhibits gastric acid
secretion, mucosal protective (suppress gastric acid secretion by inhibition of
H+/K+ATPase)
● AE: N/V/*D, *abdominal pain, dyspepsia, flatulence, headache, constipation,
toxicity: sedation, tremor, convulsions, dyspnea, abdominal pain, diarrhea,
fever, palpitations, hypotension, bradycardia
● Drug interactions: antacids
● Nursing Management: 1. Obtain serum pregnancy test before initiation
(Pregnancy X Hypersensitivity - BBW) 2. Initiate drug therapy on 2-3 day of next
period. 3. Provide verbal and written instructions to females of abortifacient
properties. 4. Assess for adequate contraception. 5. DISCONTINUE immediately
if pregnancy suspected. 6. Do not share drugs with others. 7. Report diarrhea > 1
week.
c. Antiemetic drugs (Phenothiazines & Serotonin Receptor Antagonist & Substance P)
● Protype: Promethazine (Phenothiazines)
● Indications: CNS depressants used for many reasons - also prevention and
treatment of N/V r/t surgery, anesthesia, migraines, chemotherapy, and
motion sickness (block dopamine from receptor sites in the brain and CTZ.)
● Pharmacokinetics: Rapidly absorbed oral administration, metabolism in
liver, excretion in urine.
● AE: blurred vision, urinary retention, dry mouth, photosensitivity, drowsiness,
and confusion
, ● Nursing Mangement: BBW: fatal in children <2 yrs because respiratory
depression, do not administer SQ(BBW)- IM preferred, use lowest
effective dosage, do not take with other respiratory depressant effects
concurrently.
● Prototype: Ondansetron (Zofran) (Serotonin Receptor Antagonist) pg.25
● Indications: prevent and treat N/emesis with chemotherapy,
radiation, perioperative
● Pharmacokinetics: Well absorbed in GI tract, oral onset 30-60 min. IV form
onset and peak immediately. Bioavailability slightly increased by presence of
food but unaffected by antacids.
● AE: diarrhea, constipation, headache, dizziness, rash, transient elevations in
AST/ALT, pain at injection site, Rare: bronchospasm, tachycardia, chest
pain, hypokalemia, ECG changes, tonic clonic seizures
● Nursing Management: Monitor bowel function and liver enzymes
● Prototype: aprepitant (Emend) - Substance P
● Indications: acute chemotherapy induced N/V, prevention of postoperative N/V
● Pharmacokinetics: absorbed orally, peak levels after 4 hours of administration,
highly protein bound, metabolized in the liver, excreted through urine and
feces
● AE: fatigue, weakness, dizziness, abnormal heart rhythm, headache, hiccups,
infusion site pain with IV administration. Has the potential for multiple drug
interactions.
● Nursing Management: Take medication as prescribed before the onset of N/V.
General Nursing Management for Antiemetics:
● Use measures to prevent or minimize N/V
● Assist patients to identify situations that cause or aggravate N/V
● Avoid exposure to stimuli when feasible (ex: excessive ingestion of food, alcohol, etc)
● Administer analgesics before painful diagnostic tests and dressing changes or other
therapeutic measures may be helpful, as pain may cause N/V
● Minimize activity during acute episodes of N/V - lying down and resting quietly are
often helpful
2. Describe the major laxative classifications based on the mechanism of
action, indications, side/adverse effects, and nursing management:
a. Stimulant
● Protype: Bisacodyl (Dulcolax)
● Mechanism of action: irritate GI mucosa, pulls water into bowel
● Pharmacokinetics: poorly absorbed in small intestine following oral
administration or in large intestine following rectal admin. Metabolized in
liver, primarily excreted in feces, some in urine. Half life: 16 hours
● Indication: relief of constipation, prior to surgery and medical exams,
neurogenic bowel dysfunction
, ● AE: abdominal pain, cramping, N/D, weakness
● Nursing Management: Take on empty stomach of at bedtime, swallow whole
(do not chew), do not take within an hour after ingesting milk or gastric antacids
or while receiving H2 receptor blocker therapy (this prevents abdominal
cramping and vomiting associated with premature tablet dissolution and gastric
irritation)
● Contraindicated in patients with undiagnosed abdominal pain, fecal
impaction, intestinal obstruction
b. Bulk-forming
● Protype: *Psyllium (Metamucil)
● Mechanism of action: acts within 12-24 hours, unabsorbed by body, absorbs
excess water to stimulate BM; adds bulk/size to fecal mass - pulls water into
the intestinal lumen.
● Indications: Constipation/diarrhea, bowel irregularity, lower cholesterol
(when combined with a diet low in cholesterol and saturated fat)
● AE: flatulence (severe), bloating, rare bowel obstruction
● Nursing Management: Can delay or reduce absorption of certain medications
(digoxin, carbamazepine, lithium, antidepressants, warfarin) - take 1 hour before
or 2-4 hours after taking other medications; take with 8 oz water, maintain
adequate intake of fluids (this will help improve bowel regularity)
c. Lubricant
● Protype: Mineral oil
● Mechanism of action: lubricates the fecal mass and slow colonic absorption of
water from the fecal mass (exact MOA is unknown). Effects usually occur within
6-8 hours.
● Indication: Most useful as a retention enema to soften hard, dry feces and aid
in their removal
● AE: Not recommended for long-term use - many AE: decreased absorption of fat-
soluble vitamins (A, D, E, and K) and some drugs, lipid pneumonia if aspirated
into the lungs
● Nursing Management: Do not use regularly
d. Miscellaneous
● Drug: Docusate Sodium (Colace) - Surfactant Laxative (stool softener)
● Mechanism of action: decrease the surface tension of the fecal mass to allow
water and fat to penetrate into the stool, making it softer and easier to expel
(have little true laxative effect)
● Indication: stool softener for constipation - main value is to prevent straining
while expelling stool
● AE: throat irritation, N, rash, facilitates transport of other substances, chronic
active liver disease
● Nursing Management: take daily, act within 1-3 days
● Drug Interactions (absorption): digoxin, quinidine, mineral oil, salicylates
