Pharm exam 3: Drugs for GI symptoms

GI symptoms

• Nausea and vomiting

• Motion sickness

• Constipation

• Diarrhea

• Reflux and GERD (PUD and GERD Lecture)

*Drug therapy focuses on symptom relief and

prevention of complications

Antiemetics

-Prevent or control nausea and vomiting

-Act on vomiting center and chemoreceptor trigger zone (CTZ) in brain

Antidiarrheals

Decrease stool frequency and fluids

-Reduce intestinal motility and fluid secretion

Laxatives

Promote bowel evacuation

-Increase stool water content, stool bulk, or intestinal motility

Nausea and vomiting

• Protective reflex that removes harmful substances

• Common causes: medications, infection, motion sickness,

chemotherapy, surgery

• May result from stimulation of vomiting center or CTZ

Complications of vomiting

• Dehydration

• Electrolyte imbalance

• Aspiration pneumonia

• Gastrointestinal bleeding

• Weight loss and surgical wound disruption

Antiemetics

Glucocorticoids (dexamethasone)

Used for chemotherapy-induced nausea and vomiting (CINV)

Dexamethosone complications

⚬ Adrenal insufficiency, infection, osteoporosis, glucose intolerance, PUD, sodium retention, hypokalemia

Glucocorticoids contraindications

⚬ contraindicated in patients with active, untreated infection

Antiemetics

Serotonin Antagonists (ondansetron) uses

chemotherapy radiation, post-op emesis; pregnancy

Serotonin Antagonists (ondansetron) MOA

Blocks serotonin receptors in CTZ and antagonizes

serotonin receptors that travel from upper GI to CTZ

Ondansetron complications

⚬ HA, diarrhea, dizziness, prolonged QT interval

Ondansetron Contraindications

⚬ contraindicated in patients who have QT syndrome

Antiemetics

Dopamine Antagonists (metoclopramide, prochlorperazine, promethazine) uses:

chemotherapy, toxins, and post-op emesis

Dopamine Antagonists (metoclopramide, prochlorperazine, promethazine) MOA

blockade of dopamine receptors in CTZ

Dopamine antagonists complications

⚬ Extrapyramidal symptoms (EPSs), hypotension, sedation,

anticholinergic effects

Dopamine antagonist contraindications

⚬ children and older adults- increased risk of extrapyramidal manifestations

Antiemetics

Cannabinoids (dronabinol)

used in CINV and increase appetite in patients who have AIDS

Dronabinol complications

⚬ Hypotension, tachycardia, potential dissociation

Antiemetics

Anticholinergics (scopolamine)

Used for motion sickness

-interferes with nerve impulses from vestibular apparatus

in inner ear to vomiting center in brain

Antiemetics

Antihistamines (dimenhydrinate)

Used in motion sickness

-blocks muscarinic and histaminergic receptors that

connect inner ear and VC

Promethazine (antihistamines) contraindications

⚬ respiratory depression can be severe in children

Anticholinergics and Antihistamine complications

⚬ Sedation, anticholinergic effects

Dopamine antagonists, antihistamines, and anticholinergics

contraindications

⚬ caution with urinary retention or obstruction, asthma, narrow angle glaucoma

Antiemetics

Benzodiazepine (lorazepam)

Used for CINV

-depresses nerve function at multiple CNS sites

Lorazepam complications

⚬ Sedation and paradoxical effects

Lorazepam contraindications

⚬ contraindicated with CNS depression, angle-closure glaucoma, severe hypotension

Antiemetics interactions

• Avoid sedatives, opioids, alcohol (increased CNS depression)

• Hypotensive effects of antiemetics increased with

antihypertensives

• Anticholinergic effects intensified with other

anticholingerics

Antiemetics nursing admin

• Assessment can identify underlying cause and verify if

appropriate drug is used

• CINV- administer prior to chemotherapy (combination

of 3 antiemetics more effective)

• Monitor fluid status and vital signs

• Assess for dehydration

• Provide oral care after vomiting

Constipation

• Hard, dry stool that is difficult to pass

• Common causes: low fiber intake, dehydration,

medications, inactivity

Goals of laxative therapy

• Soften stool

• Increase stool volume

• Stimulate intestinal motility

• Promote bowel evacuation

Bulk-forming laxatives (psyllium)

decrease diarrhea in patients who have diverticulosis and IBS

Psyllium MOA

soften fecal mass and increase bulk

Surfactant laxatives (docusate sodium)

softening of fecal impaction

Docusate sodium MOA

Lower surface tension of stool to allow penetration

of water

Stimulant laxatives (bisacodyl, senna)

bowel prep; constipation caused by high-dose opioid use

Bisacodyl, senna MOA

stimulate intestinal peristalsis and increase volume

of water and electrolytes in intestines

Osmotic laxatives (magnesium hydroxide, lactulose)

Low dose: episiotomy or hemorrhoids

High dose: bowel prep poison ingestion

magnesium hydroxide, lactulose MOA

draw water into intestine to increase mass of stool,

stretching musculature

Laxative complications

• GI irritation

• Rectal burning sensation

• Toxic magnesium levels

• Sodium absorption and fluid retention

• Dehydration

• Obstruction

Laxative contraindications

• fecal impaction, bowel obstruction, acute surgical abdomen to prevent perforation

• Nausea, cramping, abdominal pain

Laxatives nursing admin

• Obtain complete history of laxative use

• Take bulk-forming and surfactant laxatives with 8 oz water

• Administer bisacodyl at bedtime for results in 6-12 hours

(suppositories effective within an hour)

Laxative pt education

• Chronic use can lead to fluid and electrolyte imbalances (use occasionally, not routinely)

• Increase high-fiber foods in daily diet and increase amounts of fluid

• Maintain regular exercise regimen

Diarrhea

• Results from increased intestinal motility or decreased

fluid absorption

• Causes include infection, medications, food

intolerance

• Major concern: dehydration and electrolyte imbalance

Antidiarrheals

Prototype: diphenoxylate plus atropine MOA

⚬ Activate opioid receptors in GI tract to decrease

intestinal motility and increase absorption of fluid

and sodium in intestine

Diphenoxylate plus atropine uses

⚬ Minimize manifestations of diarrhea

⚬ Specific antidiarrheals can be used to treat underlying

cause

Diphenoxylate plus atropine contraindications

• Recommended doses: does not affect the CNS system

• High doses: can experience typical opioid effects

⚬ Unpleasant effects of atropine discourages patients taking higher doses than prescribed

• Increased risk of megacolon in patients who have inflammatory bowel disorders

• Contraindication- severe electrolyte imbalance or dehydration

Diphenoxylate plus atropine nursing admin

• Assess possible causes

• Administer initial dose, monitor response, administer further doses as needed (max dose 8 tabs/ day)

• Monitor for dehydration

Diphenoxylate plus atropine pt education

⚬ if experiencing diarrhea, drink small amounts of clear liquids or commercial oral electrolyte solution (avoid plain water)

⚬ Avoid caffeine, fried food, dairy

Prokinetic Agents

Prototype: metoclopramide MOA

• controls N/V by blocking dopamine and serotonin receptors in CTZ (reduces stimulus to empty bowels)

• augments action of acetylcholine (causes increase in upper GI motility, increasing peristalsis)

Metoclopramide uses

• IV- post-op and CINV

• PO- diabetic gastroparesis and management of GERD

Metoclopramide complications

• Tardive dyskinesia

• Extrapyramidal symptoms (EPS)

• Sedation

• Diarrhea

Metoclopramide contraindications

• Contraindicated in patients who have GI perforation, GI

bleeding, bowel instruction, and hemorrhage

• Contraindicated in patients who have seizure disorder

• Use cautiously in children and older adults (increased risk of EPS)

Metoclopramide interactions

• alcohol and CNS depressants increase risk of seizures and

sedation

• opioids and anticholinergics decrease effects of metoclopramide

Metoclopramide nursing admin

• Monitor for CNS depression and EPSs

• Can be given PO or IV

Drugs for IBS

IBS-D (alosetron)

Approved only for female patients who have severe IBS-D that is resistant to conventional management

Complication: constipation

Drugs for IBS

IBS-C (lubiprostone)

IBS with constipation in females; chronic constipation

Complication: diarrhea and nausea

Drugs for inflammatory bowel disease

Prototype: sulfasalazine MOA

decreases inflammation by inhibiting prostaglandin synthesis

Sulfasalazine uses

management of Crohn's disease; relief of mild to moderate

acute episodes of ulcerative colitis

Sulfasalazine complications

blood disorders, nausea, fever, rash

Sulfasalazine nursing admin

• Administer with foods or after meals

• Ensure at least 1200-1500 mL of daily fluid intake