Pharmacology Chapter 47 Drugs for GI Tract Disorders

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Vomiting Center

Located in the medulla, and causes vomiting. Some sensory impulses, such as odor, smell, taste, and gastric mucosal irritation, are transmitted directly here to cause vomiting.


Chemoreceptor Trigger Zone (CTZ)

Located near the medulla. Receives most of the impulses from drugs, toxins, and the vestibular center in the ear and transmits them to the vomiting center. Dopamine also stimulates this which in turn stimulates the vomiting center.


What are some nonpharmacological methods of decreasing nausea and vomiting?

  • weak tea
  • flat soda
  • gelatin
  • gatorade
  • pedialyte
  • crackers
  • dry toast

Nonprescription Antiemetics

medications given to prevent motion sickness but have a minimal effect on controlling severe vomiting resulting from anticancer agents, radiation, and toxins. Should be taken 30 minutes before travel


Nonprescription Antiemetics:

Name the drugs

These drugs inhibit vestibular stimulation in the middle ear. These drugs can be purchased OTC to prevent nausea, vomiting, and dizziness (Vertigo) caused by motion sickness.

  • dimenhydrinate (Dramamine)
  • cyclizine hydrochloride (Marezine)
  • meclizine hydrochloride (Antivert)
  • diphenhydramine hydrochloride (Benadryl)

Nonprescription Antiemetics:

Side Effects

Similar to those of anticholinergics:

  • drowsiness
  • dryness of the mouth
  • constipation

Antiemetics are no longer recommended for use in pregnant women due to the effects on the fetus. If it is severe, what antiemetic may be administered?

trimethobenzamide (Tigan)


Prescription Antiemetics:

Name the 8 groups

  1. antihistamines
  2. anticholinergics
  3. dopamine antagonists
  4. benzodiazepines
  5. serotonin antagonists
  6. glucocorticoids
  7. cannabinoids
  8. miscellaneous

Prescription Antiemetics:


Act primarily on the vomiting center; also by decreasing stimulation of the CTZ and vestibular pathways.

Side Effects: dry mouth, blurred vision caused by pupillary dilation, tachycardia (with anticholinergic use) and constipation

Contraindicated: GLAUCOMA


Prescription Antiemetics:

Dopamine Antagonists

These agents suppress emesis by blocking dopamine2 receptors in the CTZ.

Common side effects: EPS (because it blocks dopamine 2 receptors) and hypotension.

3 categories:

  1. phenothiazines
  2. butyrophenones
  3. benzodiazepines

Prescription Antiemetics:

Dopamine Antagonists: Phenothiazines

These agents suppress emesis by blocking dopamine2 receptors in the CTZ.

When used in patients with cancer, these drugs are commonly given the night before treatment, the day of treatment, and for 24 hours after. When prescribed for vomiting, the drug dose is usually smaller than when used for psychiatric disorders.

Example Drugs:

  • chlorpromazine (Thorazine)
  • prochlorperazine (Copazine)
  • promethazine (Phenergan)

Prescription Antiemetics:

Dopamine Antagonists: Butyrophenones

These agents suppress emesis by blocking dopamine2 receptors in the CTZ.

Example Drugs:

  • haloperidol (Haldol)
  • droperidol (Inapsine)

Prescription Antiemetics:

Dopamine Antagonists: Benzodiazepines

These agents suppress emesis by blocking dopamine2 receptors in the CTZ.

Example Drugs:

  • lorazepam (Ativan) drug of choice*
  • diazepam (Valium)

Lorazepam effectively provides emesis control, sedation, anxiety reduction, and amnesia when used in combo with glucocorticoid and serotonine 5-HT3 receptor antagonists.


Prescription Antiemetics:

Serotonin Receptor Antagonists

Suppress nausea and vomiting by blocking the serotonin receptors (5-HTc) in the CTZ and the afferent vagal nerve terminals in the upper GI tract. Can be administered PO or IV.

Common side effects: headache, diarrhea, dizziness and fatigue

The drugs (the most effective of all antiemetics in suppressing nausea and vomiting caused by cancer chemo-induced emesis):

  • ondansetron (Zofran)
  • granisetron (Kytril)
  • dolasetron (Anzemet)
  • palonosetron (Aloxi)

These drugs are also effective before and after surgery to prevent nausea and vomiting


Prescription Antiemetics:

Glucocorticoids (Corticosteroids)

Effective in suppressing emesis associated with cancer chemo. Administered IV and for a short while, so side effects are minimized.


  • dexamethasone (Decadron)
  • methylprednisolone (SoluMedrol)

Prescription Antiemetics:


Active ingredients in marijuana. Used to alleviate nausea and vomiting resulting from cancer treatment. Can also be used as an appetite stimulant for pts with AIDS. Contraindicated for pts with psych disorders.

  • dronabinol (Marinol)

Miscellaneous Antiemetics

These drugs suppress impulses to the CTZ.


  • diphenidol (Vontrol)
  • trimethobenzamide (Tigan)

Side Effects: drowsiness, anticholinergic symptoms


Anticholinergic symptoms include?

  1. dry mouth
  2. blurred vision
  3. urine retention
  4. constipation
  5. increased heart rate

Metotoclopramide (Reglan)

Suppresses emesis by blocking the dopamine receptors in the CTZ. Used in treatment of postop emesis, cancer chemo, and radiation. The occurrence of EPS is more prevalent in children than in adults.

High doses can cause sedation and diarrhea

Do not give to pts with GI obstruction, hemorrhage or perforation



Drugs given to induce vomiting.

Ipecac is considered appropriate in isolated cases for the pt who is alert and if administered within 60 minutes of poisoning. Instruct pt to by the ipecac syrup not the fluid extract. Should be taken with a glass of water - no milk or carbonated beverages.


When should vomiting NOT be induced?

If caustic substances such as ammonia, bleach, lye, toilet cleaners or battery acid.

Don't induce vomiting if gas, kerosene, paint thinner or lighter fluid have been ingested.


For pts with diarrhea, the loss of what places the patient at risk for metabolic acidosis?



Nonpharmacological treatments for diarrhea?

  • clear liquids
  • oral solutions (Gatorade, pedialyte)

Avoid milk products and foods rich in fat.


Traveler's Diarrhea

Also called acute diarrhea; usually caused by E. coli. Loperamide (Imodium) may be used to slow peristalsis and decrease the frequency of defication, but it can also slow the exit of the organism from the GI tract. Can be reduced by drinking bottled water, washing fruit, and eating cooked veggies...cook meat until well done.



They decrease hypermotility, but the cause of the diarrhea needs to be corrected as well.

Classified as:

  1. opiates and opiate related agents
  2. somatostatin analogue
  3. adsorbents
  4. misc antidiarrheals


Opiates and opiate related agents

They work by decreasing intestinal motility, therby decreasing peristalsis. Often combined with other antidiarrheal agents. Constipation is a common side effect. Can cause CNS depression when taken with alcohol, sedatives, or tranquilizers.


  • diphenoxylate with atropine (Lomotil)
  • Difenoxin (Motofen)

Both drugs are combined with atropine to DECREASE AB CRAMPING, INTESTINAL MOTILITY, and HYPERSECRETION.



Opiates and opiate related agents:

diphenoxylate (Lomotil) prototype drug p. 684

Contraindications: severe hepatic or renal disease, glaucoma

AVOID: alcohol, antihistamines, MAOIs, sedative hypnotics

Mode of action: decreasing intestinal motility

Side Effects: drowsiness, dilated pupils, urine retention

frequently prescribed for traveler's diarrhea




Act by coating the wall of the GI tract and adsorbing bacteria and toxins that cause diarrhea.


  • kaolin
  • pectin

Some info from the nsg process:


  1. Contraindicated if pt had liver disease, narcotic dependence, ulcerative colitis, or glaucoma
  2. For the pt with severe diarrhea, monitor bowel sounds, cardiac rhythm, electrolytes and vital signs.

What are some nonpharmacological measures for constipation?

  • Increase fiber
  • Increase fluid intake
  • Increase exercise

Laxatives and Cathartics

Used to eliminate fecal matter. Laxatives promote a soft stool and cathartic result in a soft to watery stool with some cramping.

Purgatives are harsh cathartics that cause watery stool with ab cramping.

4 types of laxatives:

  • osmotics (saline)
  • stimulants (contact or irritants)
  • bulk forming
  • emollients (stool softeners)

Osmotic (Saline) Laxatives

Serum electrolytes should be monitored to avoid electrolyte imbalance. Do NOT give to pts in HEART FAILURE. Good renal function is needed.

osmotic (saline) laxatives:

  • sodium salts
  • magnesium salts
  • Lactulose (not absorbed and draws water into the intestines to form soft stool. Decreases serum ammonia level and is useful in liver diseases like cirrhosis.)

High doses of salt saline laxatives are used for bowel prep for diagnostic and surgical procedures.

polyethylene glycol (PEG) is another laxative for bowel prep.


Osmotic (Saline) Laxatives:

Side Effects

Hypermagnesmia (drowsiness, weakness, paralysis, complete heart block, hypotension, flush and respiratory depression)

Excess use: flatulence, diarrhea, ab cramps, nausea vomiting


Stimulant (Contact) Laxatives:

Increase peristalsis by irritating sensory NERVE ENDINGS in the intestinal mucosa.


  • bisacodyl (Dulcolax)
  • senna (Senokot)
  • castor oil (Purgative)

Stimulant (Contact) Laxatives:

bisacodyl (Dulcolax)

prototype drug p. 687

Mos frequently used and abused laxative and it can be purchased OTC. Used to empty the bowel before diagnostic tests.

Contraindicated: bowel obstruction, appendicitis

side effects/adverse reactions: dependence, hypokalemia, tetany

Potassium and calcium imbalances


Bulk Forming Laxatives

Natural fibrous substances that promote large soft stools by absorbing water into the intestine, increasing fecal bulk and peristalsis. These agents are nonabsorbable.

This group doesn't cause dependence and may be used by patients with diverticulosis, IBS, iliostomy and colostomy.

  • polycarbophil (FiberCon)
  • polyethylene glycol (MiraLax)
  • methylcellulose (Citrucel)
  • psyllium (Metamucil)

Emollients (Stool Softeners)

Work by lowering surface tension and promoting water accumulation in the intestine and stool.

Used to prevent constipation; these drugs decrease straining during defecation. Mineral oil absorbs essential fat soluable vitamins ADEK.


  • docusate calcium (Surfak)
  • docusate sodium (Colace)
  • docusate sodium with senna (Peri-Colace)

A patient is prescribed lorazepam (Ativan) and a glucocorticoid during chemotherapy treatments. What is the nurse’s best action?

  1. Call the health care provider and question the order.
  2. Only administer the Ativan if the patient seems anxious.
  3. Administer the two medications at least 12 hours apart.
  4. Administer the medications and assess the patient for relief.


Drug combination therapy is commonly used to manage chemotherapy-induced nausea and vomiting. Both lorazepam (Ativan) and the glucocorticoids have been found to be effective medications to assist in preventing and managing chemotherapy-induced nausea and vomiting.


Which statement by the patient indicates that further teaching is needed about antiemetic medication?

  1. “I will not drive while I am taking these medications because they may cause drowsiness.”
  2. “I may take Tylenol to treat the headache caused by ondansetron (Zofran).”
  3. “I will apply the scopolamine patches to rotating sites on my upper arms.”
  4. “I should take my prescribed antiemetic before receiving my chemotherapy dose and continue afterwards.”


Transdermal scopolamine patches should be applied to non-irritated areas behind the ear, not on the arms. It is appropriate for the patient to refrain from driving while utilizing antiemetics, to use Tylenol to treat headaches caused by ondansetron (Zofran), and to take antiemetics preventatively prior to and after chemotherapy.


The nurse is administering loperamide (Imodium) to a patient with diarrhea. What assessment is essential for the nurse to perform?

  1. Vascular assessment
  2. Gastric assessment
  3. Hourly blood pressure measurements
  4. Intake and output every shift


Adverse effects associated with loperamide (Imodium) include central nervous system symptoms such as fatigue and dizziness, epigastric pain, abdominal cramps, nausea, dry mouth, vomiting, and anorexia. The nurse should be auscultating bowel sounds on the patient to verify that they are present in each quadrant. There is no evidence to support vascular assessment or hourly blood pressure measurements. Although intake and output is important because the patient is experiencing diarrhea, it does not have the priority that gastric assessment does.


Which outcome assessment is essential to monitor for in the patient taking diphenoxylate with atropine (Lomotil)?

  1. Increase in bowel sounds
  2. Increase in number of bowel movements
  3. Decrease in gastric motility
  4. Decrease in urination


Diphenoxylate with atropine (Lomotil) acts on the smooth muscle of the intestinal tract to inhibit gastrointestinal motility and excessive propulsion of the gastrointestinal tract (peristalsis). A decrease in the gastric motility results in a decrease in the number of bowel movements. Bowel movements should not increase; bowel sounds should not increase, and there should be no change in urination.


What will the nurse teach the patient about the reason for administering multiple medications for relief of nausea and vomiting?

  1. Combination therapy decreases the risk of constipation.
  2. Combination therapy is more cost-effective.
  3. Combination therapy blocks different vomiting pathways.
  4. Combination therapy decreases side effects due to lower doses of each drug.


Combining antiemetic agents from various categories allows the blocking of the vomiting center and chemoreceptor trigger zone through different pathways, thus enhancing the antiemetic effect.


In developing a plan of care for a patient receiving an antihistamine antiemetic agent, which nursing diagnosis is of highest priority?

  1. Knowledge deficit regarding medication administration
  2. Fluid volume deficit related to nausea and vomiting
  3. Risk for injury related to side effects of medication
  4. Alteration in comfort related to nausea and vomiting


Although all of the options are appropriate nursing diagnoses, fluid volume deficit is the highest priority because it has the highest associated mortality rate.


What instruction is most important for the nurse to teach a patient who is taking an anticholinergic agent to treat nausea and vomiting?

  1. “Assess your stools for dark streaks.”
  2. “Do not take more than two doses of this medication.”
  3. “Brush your teeth and gargle to help with dryness in your mouth.”
  4. “Check your heart rate and call the health care provider if it gets below 50 beats/min.”


Anticholinergic agents block the parasympathetic nervous system, which causes the body to “rest and digest.” Blocking of these effects leads to constipation, urinary retention, and decreased secretions (dry mouth).


Which nursing intervention is a priority before administering magnesium hydroxide to a patient?

  1. Obtain a history of constipation and causes.
  2. Record baseline vital signs.
  3. Assess renal function.
  4. Advise the patient to take the medication with a glass of water.


Adequate renal function is needed to excrete excess magnesium. This intervention is essential to predict how the patient will handle the therapy. The other interventions are important, but assessing renal function is the priority.


Which assessment is most important for the patient who is taking stimulant laxatives?

  1. Monitor bowel elimination daily.
  2. Monitor intake and output.
  3. Monitor signs and symptoms of fluid and electrolyte imbalance.
  4. Monitor heart rate and blood pressure every 4 hours.


Fluid and electrolyte imbalance is a serious complication of the therapy. The patient needs to be monitored for potential problems.


A patient is prescribed scopolamine. What information should the nurse include on the teaching plan for this patient? (Select all that apply.)

  1. “Do not take this medication if you are dizzy.”
  2. “Do not use laxatives while on this medication.”
  3. “Do not use this medication for longer than a day.”
  4. “After 3 days, switch patch to alternate ear.”
  5. “Apply patch 4 hours before effect is desired.”
  6. “Drowsiness is a concern while on this medication.”

4 5 6

This medication is used for motion sickness and has anticholinergic side effects, including dizziness, drowsiness, dry mouth, and constipation. The patient can use it for longer than 3 days, but must switch ears. It should be applied 4 hours before the effect is needed.


Ondansetron (Zofran) has been ordered for the patient undergoing cancer chemotherapy to control the severe nausea and vomiting. What side effects should the nurse observe for?

A.Headache, dizziness, and fatigue

B.Anorexia and hair loss

C.Abdominal cramping and irritability

D.Psychosis and middle ear disturbances

Answer: A

Rationale: Side effects of ondansetron (Zofran) include headache, dizziness, and fatigue.


Bisacodyl (Dulcolax) has been ordered for a patient who is constipated. The nurse realizes that Dulcolax

A.increases peristalsis to produce a bowel movement. incompatible with alcohol consumption.

C.should be avoided during pregnancy as it is teratogenic.

D.may lead to paralytic ileus.

Answer: A

Rationale: Dulcolax increases peristalsis by direct effect on intestinal smooth muscle. Alcohol and pregnancy are not affected by Dulcolax. Dulcolax does not cause paralytic ileus.


A patient is ordered a phenothiazine antiemetic for treatment of nausea and vomiting associated with chemotherapy. The drug will be most effective if administered requested by the patient.

B.1 hour after chemotherapy administration.

C.the night before treatment, the day of treatment, and for 24 hours after treatment.

D.the day of treatment.

Answer: C

Rationale: When used in patients with cancer, phenothiazine antiemetics are commonly given the night before treatment, the day of treatment, and for 24 hours after treatment.


A toddler ingests a small amount of household cleaning fluid. What is the safest advice for the nurse to provide the caregiver?

A.Give the child fluids and proceed to the emergency department.

B.Call the poison control center and follow directions.

C.Administer syrup of ipecac and monitor for vomiting.

D.Have the toddler eat bread to absorb the substance.

Answer: B

Rationale: It is safest to call the poison control center and follow directions. Fluids should not be ingested because the caustic substance may spread, causing more tissue damage. Ipecac syrup should not be administered routinely in the management of poisoned individuals.


A patient is ordered bisacodyl (Dulcolax). Before administering the drug, it is most important for the nurse to assess the patient for what?



C.Allergy to penicillin


Answer: D

Rationale: Contraindications to use of bisacodyl (Dulcolax) include hypersensitivity, fecal impaction, intestinal/biliary obstruction, GI bleeding, appendicitis, abdominal pain, nausea, vomiting, rectal fissures.


Lactulose is ordered for a patient with liver disease. What would indicate the medication is exerting a positive therapeutic effect on the patient?

A.Decreased ascites

B.Decreased ammonia level

C.Decreased jaundice

D.Decreased blood pressure

Answer: B

Rationale: Lactulose, another saline laxative that is not absorbed, draws water into the intestines to form a soft stool. It decreases the serum ammonia level and is useful in liver diseases, such as cirrhosis.

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