Unit 9 Ch. 35: Pharmacotherapy of Bowel Disorders + GI Alterations

Constipation

infrequent passage of hard, small stools, commonly caused by slow motility thru large intestine

Laxatives

drugs given to promote emptying of large intestine by stimulating peristalsis, lubricating the fecal mass, or adding more bulk to the colon contents

Cathartic

stronger and more complete bowel emptying

- drug of choice preceding diagnostic procedures of the colon

Laxative pharmacotherapy with operations

- postoperatively, to prevent straining or bearing down

- pre-operatively, to cleanse the bowel prior to procedures of the colon or GU tract

Reasons for prophylaxis of constipation

- MI or rectal pathology to prevent straining

- other drugs known to cause constipation

- bedridden or unable to exercise

- older adults with weak abdominal or perineal muscles

Reasons for treatment of constipation

- relieve simple, chronic constipation

- accelerate removal of toxic substances after OD or poisoning

- accelerate removal of dead parasites after anti-helminthic drug therapy

- cleanse the bowel prior to procedures of the colon or GU tract

Bulk-forming agents

absorb water, thus adding size to the fecal mass

- prophylactic to prevent constipation

- must be taken with lots of water

Stool softeners (surfactants)

reduce surface tension by causing more water and fat to be absorbed into the stool

- used for recent surgery, sudden lifestyle changes, MI (avoid straining)

- withhold if diarrhea occurs

- contraindicated in sodium restriction, renal impairment

Stimulants

irritate the bowel to increase peristalsis; may cause cramping and diarrhea, rapid and potent

- risk of bowel rupture if obstruction present

- used as bowel prep

- risk of dehydration

Osmotic laxatives

not absorbed in the intestine, pull water into the GI tract and fecal mass to create a more watery stool; ex. saline

- risk of dehydration

- potent, fast, bowel prep

Mineral oil, docusate

miscellaneous stool softeners; acts within the intestine by lubricating the stool and colon mucosa, encourages movement of water and fats into bowel

- can interfere with absorption of fat-soluble vitamins

Nursing implications - laxatives

- assess abdomen for distention and bowel sounds, assess bowel patterns

- assess for esophageal obstruction, intestinal obstruction, fecal impaction, abdominal pain (risk for bowel perforation)

- lots of water

Psyllium mucilloid (Metamucil)

Prototype bulk-forming laxative; insoluble fibre, indigestible, not absorbed from GI tract

- when taken with water, swells and increases size of fecal mass, stimulation the defecation reflex

- may cause obstruction if not taken with enough water

Diarrhea

increase in the fluidity of feces that occurs when the colon fails to reabsorb enough water

- can cause significant loss of body fluids and may lead to acid-base or electrolyte disorders

Common causes of diarrhea

- infection

- drugs

- inflammation

- foods

- malabsorption

Infections causing diarrhea

most commonly viral and bacterial, ex. E. coli, Salmonella, Shigella, Staphylococcus, etc

- treated with antibiotics or antiparasitics

Drugs causing diarrhea

- antibiotics kill normal intestinal flora, allowing opportunistic pathogens to grow

- laxatives, digoxin, NSAIDs, etc

- treated by discontinuing the drug, lowering the dose, or substituting

Inflammation causing diarrhea

ulcerative colitis, Crohn's disease, IBS, inflame the bowel mucosa

- treated with anti-inflammatory drugs

Foods causing diarrhea

dairy products, capsaicin (hot pepper), chronic alcohol ingestion

Malabsorption causing diarrhea

diseases of small intestine and pancreas can cause insufficient absorption of foods and fluids

Crohn's disease

ulceration in distal portion of small intestine

- discontinuous lesions

Ulcerative colitis

erosions in the large intestine

- continuous lesions

Inflammatory bowel disease

inflammation of the colon and small intestine, Crohn's + ulcerative colitis; alternating remission and exacerbation

treated with anti-inflammatory meds of immunosuppressants

Irritable bowel syndrome (IBS)-M

alternates between constipation and diarrhea; pharmacotherapy difficult, may worsen symptoms > symptomatic treatment

- altered GI motility, increased peristalsis, increased pain sensitivity of GI tract

IBS-C

constipation predominant IBS

IBS-D

diarrhea predominant IBS

Opioids

most effective for symptomatic treatment of diarrhea; slows peristalsis in colon, allows for more absorption of fluids and electrolytes, slight risk of dependence

- most common codeine and diphenoxylate

Nursing implications - antidiarrheals

- assess hydration status, serum K+, potassium, Mg2+, bicarbonate

- assess for blood in stool

- assess hepatic and renal function

- should not be used when constipation should be avoided, or with dehydration, electrolyte imbalances, liver and renal disorders, glaucoma

- drowsiness

Diphenoxylate with atropine (Lomotil)

prototype opioid antidiarrheal; slows peristalsis, allowing time for water reabsorption and formation of more solid stools

- atropine to discourage overuse

- no analgesic properties

Vomiting

defence mechanism to rid body of toxic substances

- primarily controlled by vomiting centre in medulla

- can cause metabolic alkalosis, vascular collapse

Vomiting centre

in medulla, receives sensory signals from digestive tract, inner ear, and cerebral cortex; directly sense presence of toxic substances in blood

Dehydration from vomiting

large amounts of fluid lost > water in the plasma moves from the blood to other body tissues; contents lost from stomach are strongly acidic > metabolic alkalosis

Antiemetics

Treat nausea and vomiting

Pharmacotherapy of motion sickness

anticholinergics or antihistamines

Pharmacotherapy of antineoplastic nausea + vomiting

phenothiazines, glucocorticoids, serotonin receptor blockers, neurokinin receptor antagonists

Emetics

drugs that stimulate the vomiting reflex; for ingestion of poisons and oral drug ODs

- for emergency, only when client is alert (aspiration risk)

Nursing implications - antiemetics

- assess for sedation and vomiting > NG tube

- contraindicated in hypersensitivities, bone marrow depression, coma, unknown cause of vomiting

- drowsiness, orthostatic hypotension

Prochlorperazine

prototype phenothiazine antiemetic; prescribed for severe nausea and vomiting

- blocks dopamine receptors, inhibiting signals to vomiting centre

- anticholinergic effects (dry mouth, sedation, etc)

- extrapyramidal symptoms

Ondansetron (Zofran)

prototype antiemetic; blocks serotonin receptors in GI tract and chemoreceptor trigger zone in brain to prevent nausea and vomiting caused by antineoplastic therapy

IBD pharmacotherapy

1. 5-ASA agents

2. oral corticosteroids (topical anti-inflammatory effect)

3. immunosuppresants (extend time between relapses)

or biologic therapies (expensive, risk of infections)

Sulfasalazine (Salazopyrin)

prototype 5-ASA, anti-inflammatory, sulphonamide; treats ulcerative colitis, metabolized to two active metabolites by colon bacteria = anti-inflammatory properties

IBS treatment

- dietary management

- symptomatic therapy

- drugs that regulate intestinal motility

- lifestyle changes (stress)

Pancreatitis

results when amylase and lipase remain in the pancreas rather than being released into duodenum > enzymes escape into surrounding tissue = inflammation

Acute pancreatitis

- middle-aged adults; gallstones in women, alcoholism in men

- symptoms sudden after fatty meal or alcohol; continuous, severe pain in epigastric area that radiates to back

Pharmacotherapy of acute pancreatitis

- meperidine (pain)

- H2 blockers, PPIs (reduce/neutralize gastric secretions)

- carbonic anhydrase inhibitors, antispasmodics (decrease secretion of pancreatic enzymes)

- IV fluids, parenteral nutrition

Steatorrhea

the passing of bulky, foul-smelling, fatty stools; occurs late in course of chronic pancreatitis

Chronic pancreatitis

commonly associated with alcohol

- chronic epigastric or LUQ pain, anorexia, nausea, vomiting, weight loss, steatorrhea

Pharmacotherapy of chronic pancreatitis

- may require insulin

- antiemetics

- pancreatic enzyme supplements

Alcohol causing chronic pancreatitis

thought to promote formation of insoluble proteins that occlude pancreatic duct > pancreatic juice prevented from flowing into duodenum > remains in pancreas, damages cells, causes inflammation

Nursing implications - pancreatic enzyme replacement therapy

- assess pain, breathing patterns, symmetry of chest wall, movement of chest (risk for atelectasis and ineffective breathing patterns)

- monitor for hypoventilation, hypocapnia

- monitor nutritional and hydration status

- contraindicated in allergies to pork protein or enzymes

Pancrelipase

prototype pancreatic enzyme supplement; contains lipase, protease, and amylase of porcine origin

- breakdown and conversion of lipids, starches, and proteins

- replacement therapy for insufficient pancreatic exocrine secretions

Micro-organisms of the bowel

- metabolize bile salts, estrogens, androgens, lipids, carbs, nitrogenous substances, meds

- protect against infection

- breakdown proteins not digested or absorbed = ammonia

- synthesize vit. K and some B

- produce flatus

Hypoactive bowel activity

less than 6 sounds per minute

Hyperactive bowel activity

greater than 32 sounds per minute

PEG

osmotic laxative; stir and dissolve in 4-8 oz of beverage > BM in 1-3 days

Lactulose

osmotic laxative; not digested or absorbed

when digested by colonic bacteria, draws water into colon and produces laxative effect; reduces ammonium levels by trapping in the bowel

Saline laxatives

causes movement of water and electrolytes into bowel; produces BM in 3-6 hrs

- ex. magnesium sulphate, magnesium phosphate

Bisacodyl, Senna

stimulant laxatives; stimulate the nerves of the intestines, increasing peristalsis

- retain suppository for 15-20 mins, BM in 15 mins

Bowel protocol level 1

fruitlax (except diabetics and renal pts); if no BM in 24 hrs, move to level II

Bowel protocol level II

sennosides 12-24 mg PO HS; if no BM for further 24-48 hrs, move to level III

Bowel protocol level III

- sennosides 24-36 mg PO HS

- bisacodyl 10 mg SUPP and glycerin SUPP in AM

if suppositories ineffective, give sodium phosphate (fleet) enema; if still ineffective administer mineral oil enema

Bowel protocol level IV

if still no BM, notify physician

Types of anti-diarrheals

adsorbents, antimotility, and probiotics

Adsorbents

anti-diarrheals that coat the walls of the GI tract and bind the causative bacteria or toxin for elimination

- ex. Bismuth subsalicylate, activated charcoal, aluminum hydroxide

Bismuth subsalicylate

adsorbent antidiarrheal; decreases the flow of fluids and electrolytes into the bowel, reducing inflammation within the intestine

- contains salicylate

- can cause darkened tongue

- shake well before use, swallow tabs whole

Anti-motility agents

slow peristalsis; anticholinergics and opiate-like meds

Anticholinergics

anti-motility agents that work on the smooth muscle of the GI tract to inhibit propulsion and decrease gastric acid secretion

- ex. atropine, hyoscyamine

- do not use if suspecting a bowel obstruction

Anticholinergics adverse effects

- CNS effects (headache, dizziness, anxiety, drowsiness)

- urinary retention

- sexual dysfunction

- dry mouth

Opiate-like agents

anti-motility agents; stimulate the release of ACh and prostaglandins, which reduces peristalsis and decreases transit time

- decreases flow of fluid and electrolytes into the bowel, inhibits peristalsis

- ex. loperamide, codeine, opium tincture

Opiate-like agents cautions

- don't give to child < 2 yrs

- risk for dysrhythmias with high dose

- contraindicated in E. coli, UC, PMC

Probiotics

help replenish normal bacterial flora in GI tract; often used with antibiotics to prevent diarrhea

- gas, bloating side effect

Octreotide and telotristat

used for management of diarrhea associated with chemo and metastatic carcinoid tumours

- reduce production of serotonin > reduced motility and inflammation

Dopamine antagonists/prokinetics

antiemetics; domperidone, haloperidol, metoclopramide

- act on dopamine receptors

- CNS effects; anxiety to hallucinations

Antihistamine (H1 receptor blockers)

antiemetics; cyclizine, dimenhydrinate (Gravol), diphenhydramine (Benadryl)

Serotonin antagonists

antiemetics; dolasetron, granisetron, ondansetron (Zofran)

- reduce chemo and radiation-induced vomiting

- used post-operatively

- caution in CAD

Antimuscarinic (anticholinergic blockers)

antiemetics; scopolamine

Phenothiazines (antidopaminergics)

antiemetics; chlorpromazine, prochlorperazine, promethazine

Benzodiazepine

adjunctive antiemetics; clonazepam, diazepam, lorazepam

Other antiemetics

aprepitant, corticosteroids, dexamethasone, tetrahydrocannabinol

Anticholinergics, antihistamines, phenothiazines

antiemetics with anticholinergic actions; may cause dysrhythmias, require ECG monitoring

- contraindicated in glaucoma, prostatic hyperplasia, pyloric or bladder neck obstruction, biliary obstruction

- dry mouth, hypotension, sedation, rashes, constipation

Dexamethasone

steroid antiemetic; chemo-induced emesis

- alone or with ondansetron

Aprepitant

antiemetic used for chemo-induced nausea and vomiting, and prevention of post-operative nausea and vomiting

IBD 1st line drugs

5-ASA; inhibit prostaglandins

IBD 2nd line drugs

corticosteroids; inhibit prostaglandin synthesis and inhibit some functions of phagocytes and lymphocytes

IBD 3rd line drugs

- immunosuppressant drugs (azathioprine, methotrexate)

- biologic therapy (-zumab)

Blasalazide

used for UC; creates local anti-inflammatory effect

Mesalamine, osalazine, sulfalazine (5-ASA)

used for UC; inhibit prostaglandin synthesis

Drugs for D-IBS

alosetron, dicyclomide (anticholinergic), eluxadoline (opioid agonist)

Drugs for C-IBS

linaclotide, lubiprostone

Rifaximin

antibiotic for traveller's diarrhea and D-IBS