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Chapter 46

DRUGS FORGASTROINTESTINAL TRACT

DISORDERS

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Drugs for theGastrointestinal Tract

Gastrointestinal disordersVomitingToxic substance ingestion

DiarrheaConstipation

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Vomiting

Cerebral centers affecting vomiting

The chemoreceptor trigger zone and vomiting center.

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Antiemetics

Nonpharmacologic measuresWeak teaGatorade

CrackersToast

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Antiemetics (contd)

Nonprescription antiemeticsAntihistamines

Dimenhydrinate (Dramamine) Diphenhydramine (Benadryl) Side effects (similar to anticholinergics)

Drowsiness, dry mouth, constipationBismuth subsalicylate (Pepto-Bismol)

ActionActs directly on gastric mucosa to suppress vomiting

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Antiemetics (contd)

Prescriptive antihistaminesHydroxyzine (Vistaril)Promethazine (Phenergan)

Acts on VC, decreases stimulation of CTZAnticholinergicScopolamine (Transderm-Scop)Acts on VC, decreases stimulation of CTZ

Dopamine antagonistsPhenothiazines Promethazine (Phenergan)

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Antiemetics (contd)

Promethazine (Phenergan)Action

Inhibit CTZ, blocks H1 receptor sitesSide effects

Drowsiness, dry mouth, blurred vision, tachycardia,constipation, urinary retention, photosensitivity, EPS(tardive dyskinesia, acute dystonia, akathisia)

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Antiemetics (contd)

Dopamine antagonistsButyrophenones

Haloperidol (Haldol), Droperidol (Inapsine)

Action

Blocks dopamine (D2) receptors in CTZ Side effects

EPS, hypotensionMetoclopramide (Reglan)

Action Blocks D2 receptors in CTZ Side effects

Sedation, diarrhea, EPS

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Antiemetics (contd)

BenzodiazepinesLorazepam (Ativan)

UseCancer chemotherapy

Used in combination with a glucocorticoid andserotonin 5-HT3 receptor antagonist

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Antiemetics (contd)

Serotonin receptor antagonistOndansetron (Zofran)

ActionBlocks serotonin receptors in CTZ and afferent vagalnerve terminals in UGI

UseCancer chemotherapy

Side effectsHeadache, diarrhea, dizziness, fatigue

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Antiemetics (contd)

GlucocorticoidsDexamethasone (Decadron)Methylprednisolone (Solu-Medrol)

Use: cancer chemotherapyCannabinoids

Dronabinol (Marinol) Side effects

Drowsiness, dizziness, dry mouth, impaired thinking,euphoria, mood changes, headaches, confusion,depersonalization, nightmares, incoordination,memory lapse, anxiety

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Antiemetics (contd)

Miscellaneous Diphenidol (Vontrol)Trimethobenzamide (Tigan)

ActionSuppress impulses to CTZ Side effects

Drowsiness, dry mouth, tachycardia, urine retention,constipation, diarrhea, blurred vision, hypotension,EPS

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Antiemetics (contd)

Nursing interventionsProvide mouth careMonitor vital signs, bowel sounds

Monitor for dehydrationWarn not to consume alcohol when taking anantiemeticWarn pregnant females to avoid antiemeticsAvoid driving motor vehicles

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Emetics

Ipecac ( OTC)Action

Stimulates CTZ & acts directly on gastric mucosa

Use Induces vomiting after toxic substanceCaution

Avoid vomiting if substance is caustic or petroleum If vomiting contraindicated, activated charcoal is

given

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Emetics (contd)

Ipecac Administration

Use ipecac syrup, not ipecac fluid extract

Take with a glass of water or fluid, not with milk orcarbonated beverage Vomiting occurs in 15 to 30 minutes If vomiting does not occur, give activated charcoal Gastric lavage may be needed if vomiting does not

occur

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Diarrhea

Causes Spicy or spoiled foodsBacteria (Escherichia coli), virus, toxins

Drug reactionsFecal impaction, laxative abuseMalabsorption disorders, bowel tumor,inflammatory bowel diseaseStress, anxiety

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Antidiarrheals

Purpose Decrease hypermotility

CautionShould not be used for more than 2 days or iffever is present

Types Opiates and opiate-related agentsSomatostatin analogAdsorbents

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Antidiarrheals (contd)

Opiates and opiate-related agentsParegoric (camporated opium tincture)Diphenoxylate with atropine (Lomotil)

Loperamide (Imodium) Opiates decrease GI motility Opiates may cause respiratory depression

Especially children and elderly May cause physical dependence Atropine contraindicated in glaucoma

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Antidiarrheals (contd)

Somatostatin analogOctreotide (Sandostatin)

Use: for severe diarrhea from cancer

AdsorbentsBismuth salts (Pepto-Bismol)Kaolin-pectin (Kaopectate)

Action: coats GI tract, absorbs bacteria or toxinsCombination agents

Parepectolin (paregoric, Kaolin-pectin)

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Antidiarrheals (contd)

Nursing interventionsMonitor BP, RReport more than 10-15 mmHg decrease inBPMonitor frequency of bowel movements andbowel soundsAssess for evidence of dehydrationMonitor electrolytesAvoid fried foods, milk, and sedativesIf diarrhea persists after 48 hrs, notify MD

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Constipation

CausesBowel obstruction, fecal impactionChronic laxative use, ignoring urge to defecateNeurologic disordersSide effect of drugsLack of exercise, fiber, water

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Constipation (contd)

LaxativesLaxatives: promote soft stoolCathartics: soft to watery stool with crampingPurgatives: watery stool with cramping

Types of laxativesOsmotic (saline)Stimulant (irritants)Bulk-formingEmollient (stool softeners)

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Osmotic (Saline) Laxatives

Polyethylene glycol (GoLYTELY)Lactulose (Chronulac)Action

Hyperosmolar salts pull water into colon,increase water in feces to increase bulk, whichstimulates peristalsis

Side effects

Fluid and electrolyte imbalances, hypotension,weakness

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Stimulant (Irritant) Laxatives

Phenolphthalein (Ex-Lax, Correctol)Bisacodyl (Dulcolax)Action

Increase peristalsis by irritating sensory nerveendings in intestinal mucosaResults : orally 6-12 hrs, supp 15-60 minSide effects

Abdominal cramps, weakness, reddish brownurine, diarrhea

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Bulk-Forming Laxatives

Psyllium hydrophilic mucilloid(Metamucil)Calcium polycarbophil (Fiber-Con)

Action Absorb water into intestines, increase bulk andperistalsis

Results 8-12 hrs

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Bulk-Forming Laxatives

AdministrationMix in glass of water or juice, stir, drinkimmediately, follow with 1 glass water

Side effectsAbdominal crampsExcess laxative

Nausea,vomiting, gas, diarrhea

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Emollients (Stool Softeners)

Docusate (Colace)Action

Lowers surface tension

Promotes water accumulation in intestineEmulsifies and lubricates feces for easierpassage

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Emollients (Stool Softeners)(contd)

UsePrevents constipationReduces straining post surgery or myocardialinfarction

Side effectsAbdominal cramping, nausea, vomiting,diarrhea

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Laxatives

ContraindicationsUndiagnosed abdominal painInflammatory disorders of the GI tract

Appendicitis, diverticulitis, ulcerative colitisSpastic colonBowel obstructionPregnancy

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Case Study

A client who is taking chemotherapy forcancer of the right kidney is extremelynauseated and vomiting.

Critical ThinkingWhich types of antiemetic are appropriatefor cancer chemotherapy?

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Practice Question #1

Ondansetron (Zofran) has been ordered forthe client who is taking cancerchemotherapy to control the severe nausea

and vomiting. What side effects arepossible?A. Headache, dizziness, and fatigueB. Constipation, anxiety, and fever

C. Abdominal cramping and irritabilityD. Psychosis and middle ear disturbances

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Practice Question #1 (contd)

Answer: A. Rationale: Side effects ofondansetron (Zofran) include headache,dizziness, and fatigue. Constipation, anxiety,

fever, abdominal cramping, irritability,psychosis, and middle ear disturbances arenot side effects/adverse effects ofondansetron.