This document summarizes drugs used to treat gastrointestinal disorders. It discusses antiemetics for vomiting, antidiarrheals for diarrhea, laxatives for constipation, and anti-ulcer drugs. It describes the causes and types of each condition and classifies the drugs by their mechanisms of action, including opiates, anticholinergics, antacids, H2 blockers, PPIs, pepsin inhibitors, and prostaglandin analogues. Common side effects are also outlined for each drug class.

1. GASTROINTESTINAL DRUGS

2. DRUGS FOR GASTROINTESTINAL
DISORDERS
• Vomiting, diarrhea, and constipation are GI problems that frequently
require drug intervention.
• Drugs used to correct or control vomiting, diarrhea, and constipation are
Antiemetics, Emetics, Antidiarrheals, and Laxatives

3. VOMITING
• Vomiting (emesis), the expulsion of gastric contents, has a multitude of
causes, including motion sickness, viral and bacterial infection, food
intolerance, surgery, pregnancy.
• Two major cerebral centers—the chemoreceptor trigger zone (CTZ),
which lies near the medulla, and the vomiting center in the medulla—
cause vomiting when stimulated.
• Nonpharmacologic measures should be used first when nausea and
vomiting occur. If the nonpharmacologic measures are not effective,
antiemetics are combined with nonpharmacologic measures.
• 2 GROUPS OF ANTIEMETICS
• NON-PRESCRIPTION
• PRESCRIPTION

4. NONPHARMACOLOGIC MEASURES
• The nonpharmacologic methods of decreasing nausea and vomiting
include administration of weak tea, flat soda, gelatin, Gatorade, and
Pedialyte (for use in children). Crackers and dry toast may be helpful.
When dehydration becomes severe, intravenous (IV) fluids are needed to
restore body fluid balance.
ANTIEMETICS IN PREGNANCY
• Antiemetics that were once frequently used for the treatment of nausea
and vomiting during pregnancy are no longer recommended because
they may cause harm to the fetus.
• Instead, nonpharmacologic methods are used when possible to alleviate
nausea and vomiting during pregnancy. Ginger and red raspberry leaf
tea have been used effectively but are not regulated by the US Food and
Drug Administration (FDA). If vomiting becomes severe and threatens
the well-being of the mother and fetus, an antiemetic such as
promethazine or metoclopramide can be administered.

5. NONPRESCRIPTION ANTIEMETICS
• Nonprescription antiemetics (ant vomiting agents) can be purchased as
over-the-counter (OTC) drugs.
• To prevent motion sickness, the antiemetic should be taken 30 minutes
before travel. These drugs are not effective in relieving motion sickness if
taken after vomiting has occurred.
• Nonprescription Antiemetics (OTC)
• DIMENHYDRINATE,
• CYCLIZINE HYDROCHLORIDE
• MECLIZINE HYDROCHLORIDE
• DIPHENHYDRAMINE HYDROCHLORIDE
• SIDE EFFECTS INCLUDE:
• DROWSINESS, DRY MOUTH, AND CONSTIPATION

6. PRESCRIPTION ANTIEMETICS
• Common prescription antiemetics are classified into the following
groups:
1. ANTIHISTAMINES
2. ANTICHOLINERGICS
3. DOPAMINE ANTAGONISTS
4. BENZODIAZEPINES
5. SEROTONIN ANTAGONISTS
6. GLUCOCORTICOIDS
7. CANNABINOIDS
8. MISCELLANEOUS

7. ANTIHISTAMINES (HYDROXYZINE)
NAUSEA, VOMITING, VERTIGO, ANXIETY, AGITATION
DROWSINESS, FATIGUE, HEADACHE, DRY MOUTH, ETC.
ANTICHOLINERGICS (SCOPOLAMINE
NAUSEA, VOMITING, MOTION SICKNESS, AND IBS
DROWSINESS, FATIGUE, HEADACHE, DRY MOUTH, ETC.
DOPAMINE ANTAGONISTS
NAUSEA, VOMITING, SCHIZOPHRENIA, ANXIETY
DROWSINESS, HYPTERTENSION, HEADACHE, INSOMNIA
BENZODIAZEPINES
PREVENTION OF CHEMO-INDUCED NAUSEA &
VOMITING & SEDATION INDUCTION
HYPERTENSION, HYPOTENSION, TACHYCARDIA
SEROTONIN ANTAGONISTS
RADIATION – CHEMO – INDUCED NAUSEA &
DIZZINESS, WEAKNESS, FATIGUE, AGITATION
CANNABINOIDS
ANOREXIA & CHEMO INDUCED NAUSEA & VOMITING
DROWSINESS, IMPAIRED COGNITION, EUPHORIA,
PARANOIA
MISCELLANOUS
POSTOPERATIVE & CHEMO-INDUCED NAUSEA AND
VOMITING
DROWSINESS, VISUAL DISTRUBANCE, FATIGUE,
HEADACHE

8. ANTIDIARRHEALS
Gastrointestinal Drugs

9. • Frequent liquid stool, is a symptom of an intestinal
disorder.
• Causes include (1) foods (spicy, spoiled), (2) fecal
impaction, (3) bacteria (Escherichia coli, Salmonella) or
viruses (parvovirus, rotavirus), (4) toxins,(5) drug
reactions, (6) laxative abuse, (7) malabsorption
syndrome caused by lack of digestive enzymes, (8)
stress and anxiety, (9) bowel tumor, and (10)
inflammatory bowel disease such as ulcerative colitis or
Crohn disease.
• Diarrhea can be mild to severe. Antidiarrheals should
not be used for more than 2 days and should not be
used if fever is present.
• Because intestinal fluids are rich in water, sodium,
potassium, and bicarbonate, diarrhea can cause minor
or severe dehydration and electrolyte imbalances.
• The loss of bicarbonate places the patient at risk
for developing metabolic acidosis. Patients with
diarrhea should avoid milk products and foods
rich in fat.
• Diarrhea can develop very quickly and can be life
threatening to young patients and older adults,
who may not be able to compensate for the fluid
and electrolyte losses.
DIARRHEA

10. NONPHARMACOLOGIC MEASURES
• The cause of diarrhea should be identified. Nonpharmacologic
treatment for diarrhea is recommended until the underlying cause can
be determined.
• This includes use of clear liquids and oral solutions such as Gatorade (for
adults) and Pedialyte or Rehydralyte (for children) and IV electrolyte
solutions. Antidiarrheal drugs are frequently used in combination with
nonpharmacologic treatment.

11. TRAVELER’S DIARRHEA
• Travelers’ diarrhea, also called acute diarrhea
• is usually caused by E. coli. It ordinarily lasts less than 2 days; however, if
it becomes severe, fluoroquinolone antibiotics are usually prescribed.
• Loperamide may be used to slow peristalsis and decrease the frequency
of defecation
• But it can also slow the exit of the organism from the GI tract. Travelers’
diarrhea can be reduced by drinking bottled water, washing fruit, and
eating cooked vegetables. Meats should be cooked until well done.

12. • There are various antidiarrheals for
treating diarrhea and decreasing
hypermotility (increased peristalsis).
• Usually an underlying cause of the
diarrhea needs to be corrected as
well. The antidiarrheals are classified
as (1) opiates and opiate-related
agents, (2) adsorbents, and (3)
miscellaneous antidiarrheals.
ANTIDIARRHEALS

14. • Opiates decrease intestinal motility,
thereby decreasing peristalsis.
• Constipation is a common side effect
of opium preparations.
• Codeine is an example. Opiates are
frequently combined with other
antidiarrheal agents.
• Opium antidiarrheals can cause CNS
depression when taken with alcohol,
sedatives, or tranquilizers. The
duration of action of opiates is
approximately 2 hours.
• Diphenoxylate with atropine is an
opiate that has less potential for
causing drug dependence than other
opiates such as codeine.
• Difenoxin is an active metabolite of
diphenoxylate, but it is more potent
than diphenoxylate.
• Both drugs are combined with
atropine to decrease abdominal
cramping, intestinal motility, and
hypersecretion.
OPIATES AND OPIATE-RELATED AGENTS

15. OPIOIDS

16. Laxatives
Gastrointestinal Drugs

17. Absorption
 When a person takes two drugs at the same
time, the rate of absorption of one or both
drugs can change.
 A drug can block, decrease, or increase the
absorption of another drug. It can do this in
one of three ways: (1) by increasing or
decreasing gastric emptying time, (2) by
changing the gastric pH, or (3) by forming drug
complexes.
 Drugs that increase the speed of gastric
emptying, such as laxatives, may cause an
increase in gastric and intestinal motility and a
decrease in drug absorption.
 Most drugs are absorbed primarily in the small
intestine; exceptions include barbiturates,
salicylates, and theophylline, which undergo
gastric absorption.

18. Gastrointestinal Disorder:
Constipation
● The accumulation of hard fecal material in the large intestine, is a
relatively common complaint and a major for older adults.
● Insufficient water intake and poor dietary habits are contributing
factors.
● Other causes include (1) fecal impaction, (2) bowel obstruction. (3)
chronic laxative use, (4) neurological disorders (paraplegia), (5)
ignoring the urge to defecate, (6) lack of exercise, and (7) select
drugs such as anticholinergics, narcotics, and certain antacids.

19. Passage of drug in gastrointestinal tract

20. Gastrointestinal system
● The gastrointestinal (GI) system, or GI tract,
comprises the alimentary canal and the digestive
tract, and begins at the oral cavity and ends at
the anus. Major structures of the GI system are
(1) the oral cavity (mouth, tongue, and pharynx),
(2) the esophagus, (3) the stomach, (4) the small
intestine (duodenum, jejunum, and ileum), (5)
the large intestine (cecum, colon, and rectum),
and (6) the anus. The accessory organs and glands
that contribute to the digestive process are (1)
the salivary glands, (2) the pancreas, (3) the
gallbladder, and (4) the liver.

21. Laxatives
Laxatives and cathartics are used to eliminate fecal matter. Laxatives
promote a soft stool, cathartics result in a soft to watery stool with
some cramping, and frequently dosage determines whether a drug
acts as a laxative or cathartic. Because these terms are often used
interchangeably. Purgatives are harsh cathartics that cause a watery
stool with abdominal cramping. There are four types of laxatives: (1)
osmotics (saline), (2) stimulants (contact or irritants), (3) bulk-
forming, and (4) emollients (stool softeners).
Laxatives should be avoided if there is any question that the patient
may have intestinal obstruction; if abdominal pain is severe; or if
symptoms of appendicitis, ulcerative colitis, or diverticulitis are
present. Most laxatives stimulate peristalsis. Laxative abuse from
chronic use is a common problem, especially in older adults

22. Anti-Ulcer Drugs
Gastrointestinal Drugs

23. The 7 Groups of Antiulcer Agents
1. Tranquilizers
2. Anticholinergics
3. Antacids
4. H2 Blockers
5. PPIs
6. Pepsin inhibitor Sucralfate
7. Prostaglandin E1 analogue misoprostol

24. Tranquilizers
- Have minimal effects in preventing and treating ulcers
- They reduce vagal stimulation and decrease anxiety
Side effects: edema, ataxia, confusion, and agranulocytosis

25. Anticholinergics
- These drugs relieve pain by decreasing GI motility and secretion. They act by
inhibiting acetylcholine and blocking histamine and HC1
- Anticholinergics delay gastric emptying time, because of this they are used more
oftenly for duodenal ulcers than for gastric ulcers.
How to use: Taken 30 minutes to 1 hour before meals, at least 2 hours after evening
meal for the bedtime dose .
Side effects: Dry mouth, decreased secretions, headache, blurred vision, dizziness,
asthenia, palpitations, erectile dysfunction, drowsiness, constipation, urinary retention

26. Antacids
- Promote ulcer healing by neutralizing HC1 and reducing pepsin activity
- There are two types: systemic effect & nonsystemic effect
Sodium bicarbonate is a systemically absorbed antacid because of its many side effects
it is used to treat peptic ulcers.
Nonsystemic effect antacids are composed of alkaline salts such as aluminum and
magnesium. When these two are combined neutralizes gastric acid without causing
severe diarrhea or constipation.

27. Histamine2 Blockers
-Histamine2 blockers prevent acid reflux in the esophagus . These drugs block the H2
receptors of the parietal cells in the stomach thus reducing gastric acid secretion and
concentration.
- The first H2 blockers were cimetidine (1975). Cimetidine has a short life and duration
of action. It blocks about 70% of acid secretion for 4 hours. 50%-80% of the drug is
excreted unchanged in the urine.
-Famotidine and nizatidine has a longer duration of action. They not only block gastric
acid secretions but they also promote healing of the ulcer.
Side effects: headache, agitation, dizziness, nausea, vomiting, constipation, diarrhea,
skin rash, vitamin b12 deficiency, erectile dysfunction, and blood dyscrasias

28. Proton Pump Inhibitors (PPIs)
- PPIs suppress gastric acid secretion by inhibiting the
hydrogen/potassium ATPase enzyme system located in the parietal
cells. They inhibit gastric acid secretion up to 90% more than H2
blockers.
- PPIs can enhance the action of digoxin, oral, anticoagulants, certain
benzodiazepines, and phenytoin because they interfere with liver
metabolism

29. Pepsin Inhibitors
- Sucralfate, a pepsin inhibitor, functions as as a “mucosal protective drug”. It
combines with protein to form a viscous substance that covers the uclerand
protects it from acid and pepsin.
- This drug does not neutralize acid or decrease acid secretion
Dosage: usually four times a day before meals and at bedtime. If it’ s for pain they
should be given either 30 minutes before or after the administered sucralfate
- Sucralfate promotes healing by adhering to the ulcer surface. Sucralfate decreases
the absorption of tetracylcine, phenytoin, fat-soluble vitamins

30. Prostaglandin Analogue Antiulcer Drug
- Misoprostol is a drug used to prevent and treat peptic ulcers. It appears to
suppress gastric acid secretion and to increase cytoprotective mucus in the GI
tract.
Side effects: headache, abdominal pain, nausea, vomiting, flatulence, diarrhea, and
constipation