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Pharmacology > GI Drugs Part 2 > Flashcards

GI Drugs Part 2 Flashcards

1
Q

What is constipation?

A

• Defined as a stool frequency of less than three per week.
• In the absence of an underlying medical condition, lifestyle modifications such as increasing dietary fiber
and physical activity are the first line strategy.
• Patients may become dependent on over-the-counter laxative use for bowel evacuation, or may abuse them in weight loss attempts.

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2
Q

What are three Bulk-forming Laxatives? Overview and contraindications?

A

• Methylcellulose
• Psyllium
• Bran
• Nondigestible colloids which absorb water to form a
bulky, soft jelly that distends the colon to promote
peristalsis.
• Relatively contraindicated in immobile patients and
patients on long term opioid therapy as intestinal
obstruction may result.

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3
Q

Cathartics (stimulant laxatives) action and three examples?

A

• Directly stimulate the enteric nervous system to
increase intestinal motility.
• Castor oil is broken down into ricinoleic acid in the
small intestine.
• Contraindicated in pregnancy as this intermediary may
cause uterine contractions.
• Bisacodyl acts at the level of the colon.
• Minimal systemic absorption, thus is safe for both acute and long term use.
• Senna
Occurs naturally in the plant of the same name.
Chronic use may lead to melanosis coli, which is a
harmless brown pigmentation of the colonic
mucosa that is unrelated to colon cancer risk.

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4
Q

Name 2 stool softeners and moa?

A

• Docusate
• Glycerin
• Surfactants which allow water to penetrate and
thereby soften formed stool in the bowel.

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5
Q

What is a lubricant laxative and moa?

A

• Mineral oil
• Coats fecal material preventing water reabsorption.
• Should not be given with docusate as the mineral
oil will be absorbed into the stool thereby negating
its laxative effect.

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6
Q

What are 3 osmotic laxatives, moa, ae, and contraindication?

A

• Lactulose
• Magnesium salts such as magnesium hydroxide,
magnesium sulfate.
• Nonabsorbable sugars or salts which exert an osmotic
pull to retain water in the intestinal lumen.
• Lactulose is metabolized by colonic bacteria and can
lead to severe flatus with cramping.
• Magnesium salts should not be used for prolonged
periods in persons with renal insufficiency as they may
cause hypermagnesemia.

Polyethylene glycol (PEG)
• Water soluble polymer
• Low toxicity and negligible systemic absorption.
• Generates high osmotic pressures in the gut lumen.
• Commonly used for complete bowel preparation
before gastrointestinal endoscopic procedures.
• Does not produce significant flatus or cramping.
May be preferred for management of chronic
constipation in selected patients.

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7
Q

Lubiprostone moa, indications, ae, and contraindications?

A

• Stimulates the type 2 chloride channels of the
small intestine.
• Increases the secretion of chloride à intestinal motility.
• Indications:
• Chronic constipation including irritable bowel syndrome with predominant constipation.
• Most common adverse effect - diarrhea.
• Contraindicated in children.

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8
Q

Selective Mu-Opioid Receptor Antagonists 2 examples, overview, and action.

A

• Alvimopan
• Methylnaltrexone
• Both acute and chronic use of opioid analgesics causes
constipation due to decreased intestinal mobility.
• This adverse effect is not subject to tolerance.
• Selective mu-opioid receptor antagonists do not cross the blood-brain barrier and thus do not negate the
analgesic effect of opioids.
• Act at the level of the gut to maintain normal motility.

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9
Q

Name 2 opioid agonists and overview?

A

• Loperamide
• Diphenoxylate
• Analogs of the opioid meperidine which activates
presynaptic mu-opioid receptors in the enteric
nervous system to inhibit ACh release and decrease
gut peristalsis.

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10
Q

Characteristics of Loperamide and dioxyphenolate? Contraindications?

A

• Loperamide - low potential for addiction as it has
no analgesic/euphoric properties.
• Dioxyphenolate - higher doses can have CNS
effects and, with prolonged use, lead to opioid
dependence.
• Both drugs are contraindicated in children and patients with severe colitis

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11
Q

Somatostatin Analogs example, indications?

A

• Somatostatin is a key endogenous regulatory
peptide of enteric function.
• Octreotide is a synthetic octapeptide with thirty
times the serum half-life of somatostatin.

• Indications:
• Secretory diarrhea due to neuroendocrine tumors
such as carcinoid and VIPoma.
• Diarrhea caused by vagotomy, dumping syndrome,
short bowel syndrome and AIDS.

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12
Q

Somatostatin AE?

A
  • Adverse effects:
  • Decreased pancreatic exocrine function.
  • Resultant steatorrhea can lead to deficiency of fat-soluble vitamins.
  • Inhibition of gallbladder contractility leads to the formation of biliary sludge which may precipitate to gallstones.
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13
Q

Overview of Bismuth compounds?

A

• Bismuth subsalicylate (e.g. Pepto-Bismol)
• Controls traveler’s diarrhea by decreasing fluid
secretion in the enteric tract.
• This effect is due to both its coating action and the
salicylate component.

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14
Q

What is Irritable Bowel Syndrome?

A

• Functional disorder of chronic abdominal pain
associated with altered bowel habits in the absence
of an organic gastrointestinal disease.
• Classified according to predominance of diarrhea or
constipation.
• Patients treated according to symptomatic subtype.

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15
Q

First line strategy for IBS?

A

• First line strategy does not involve medication.
• Patients may keep a food diary and try sequential:
1. Exclusion of gas-producing foods.
2. Low fermentable oligo-, di-, and
monosaccharides and polyols (FODMAPs).
3. Lactose and/or gluten omission.

• Moderate to severe symptoms of irritable bowel
syndrome (IBS) that impair quality of life qualify for
pharmacologic intervention.
• Constipation predominant IBS - chloride channel
activator laxative lubiprostone.

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16
Q

Diarrhea predominant IBS pharmacological intervention?

A
  1. Opioid agonists such as loperamide.
  2. The 5-HT3 antagonist alosetron - inhibits afferent 5- HT3 receptors to reduce noxious visceral sensations
    such as bloating, nausea and pain.
  3. Anticholinergics such as hyoscyamine, dicyclomine,
    glycopyrrolate and methscopolamine – antispasmodic effect on the G.I. tract.
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17
Q

Role of Anticholinergics in IBS?

A

• Small or large bowel spasm has not been found to be an important cause of IBS symptoms.
• Also, cholinergic blockade results in many
unpleasant side effects.
• The use of anti-cholinergics is now limited to shortterm relief of acute diarrhea predominant
episodes.

18
Q

What is Inflammatory Bowel Disease?

A

Ulcerative colitis and Crohn’s disease together
comprise the clinical entity of Inflammatory
Bowel Disease (IBD).
The selection of pharmaceutic treatments for
IBD is guided by:
1.Symptom severity and responsiveness
2.Anatomic distribution of disease
3.Drug toxicity

19
Q

Name 3 aminosalicylates?

A
  • Sulfasalazine
  • Balsalazide
  • Mesalamine
20
Q

aminosalicylates use and active group?

A

• Used for long term maintenance of IBD remission.
• Active group is 5-aminosalicylic acid (5-ASA).
• Exact mechanism of action of 5-ASA remains
unknown.

21
Q

Aminosalicylates MoA Theories?

A

• Modulation of both the cyclooxygenase and lipoxygenase pathways.
• Inhibition of the activity of nuclear factor-κB (NF-κB), an
important transcription factor for proinflammatory
cytokines.
• Inhibition of cellular immunity mechanisms.
• Scavenges reactive oxygen metabolites.

Gross reduction of inflammatory
mediators with resultant control of IBD
processes.

22
Q

Factors that determine clinical efficacy for Aminosalicylates and PK?

A

• The clinical efficacy of 5-ASA depends on achieving
high concentrations at the target sites.
• Suppository or enema forms are useful in patients
with isolated sigmoid colon or rectal disease.

PK:
• Orally administered 5-ASA would be almost
completed absorbed in the jejunum.
• No therapeutic effect in the more distal ileum,
colon and rectum would be obtained.

23
Q

Sulfasalazine overview?

A

Sulfasalazine consists of 5-ASA linked to sulfapyridine by an azo bond.
• The sulfapyridine group functions to reduce
absorption of this formulation in the jejunum after
oral ingestion, resulting in higher drug availability
in the distal small intestine and colon.

24
Q

Sulfasalazine MOA?

A
  1. The majority of the given dose passes into the colon, where sulfasalazine is reduced by coliform bacterial enzyme, azoreductase, to sulfapyridine and 5-ASA.
  2. 5-ASA is able to act
    therapeutically in the colon and may even “backwash” into the terminal ileum to act there.
25
Q

AE of sulfasalazine?

A

• Up to 40% of patients are unable to tolerate
sulfasalazine.
• Adverse effects are dose related and commonly include nausea, GI upset, headaches, arthralgias, myalgias, bone marrow suppression and hypersensitivity reactions.
• Most of these side effects are attributed to systemic
absorption of the sulfapyridine group.

26
Q

Overview of Balsalazide?

A

• Balsalazide consists of one 5-ASA linked to an inert,
unabsorbed carrier molecule.
• Similarly, this formulation will deliver maximal
amounts of 5-ASA to the colon.
• The inert carrier molecule causes no adverse
effects. Balsalazide is generally well tolerated.

27
Q

Overview of Mesalamine?

A

• Mesalamine - physically packaged 5-ASA in
timed-release or pH sensitive microgranules
that release the active drug into the desired
specific portion of the gut actively affected by
IBD.
• Balsalazide is generally well tolerated.

28
Q

Name 3 glucocorticoids and the action of glucocorticoids?

A

• Prednisone
• Prednisolone
• Budesonide
• Used to induce remission of acute exacerbations of IBD.
• Not indicated for maintaining remission.
• Immunosuppressive and anti-inflammatory effects via :
• interaction with intracellular glucocorticoid response
elements.
• inhibition of phospholipase A2 and cyclooxygenase.
• inhibition of nuclear factor-κB.

29
Q

Glucocorticoids pk and ae?

A

• Prednisone and prednisolone have an intermediate duration of action which allows for once daily dosing.
• Glucocorticoids of choice for oral therapy in IBD.
• Hydrocortisone is administered via enema for sigmoid and
rectal IBD flares.
• IBD patients treated with these drugs are subject to steroid adverse effects including adrenal suppression, hyperglycemia, immunosuppression and osteoporosis.

30
Q

Overview of Budesonide?

A

• Budesonide – used for topical effects on the
luminal surface of inflamed bowel.
• Following enteric absorption, undergoes rapid first- pass metabolism thus has low systemic
bioavailability.
• The benefit of using budesonide is the significantly decreased rate of systemic adverse effects as compared to prednisolone.

31
Q

Name 2 immunosuppressants? Overview of action?

A

• Mercaptopurine (6-MP)
• Azathioprine
• Immunosuppressive purine metabolites.
• Indicated for induction and maintenance of IBD
remission.
• Steroid sparing effect.
• Dose related toxicities - nausea, vomiting, hepatotoxicity and bone marrow depression.

32
Q

Immunosuppressive Purine

Metabolites moa, ae and use guidelines?

A

ol markedly reduces xanthine oxidase activity.
• Xanthine oxidase breaks down 6-MP.
• Co-administration of allopurinol with 6-MP can
precipitate life threatening leucopenia.
• Allopurinol is to be used with caution in patients
taking 6-MP or azathioprine.

33
Q

Methotrexate moa, dosage?

A

• Methotrexate
• Inhibits dihydrofolate reductase, an enzyme
important in the production of thymidine and
purines.
• Given at relatively low doses which do not have
antiproliferative effects.
• Reduces the inflammatory actions of Interleukin-1.

34
Q

Methotrexate AE?

A

• Adverse effects - bone marrow depression,
megaloblastic anemia and mucositis.
• The risk of these adverse effects is reduced by
folate supplementation.
• Folate supplementation does not reduce the antiinflammatory
actions of the drug.

35
Q

Anti-TNF-α Drugs?

A
  • Infliximab
  • Adalimumab

• Bind and inactivate human Tumor Necrosis Factor
(TNF).
• Indicated in acute and chronic treatment of IBD.
• Infliximab - for moderate to severe colitis which is
not responsive to mesalamine or corticosteroids.

36
Q

TNF is a key mediator of?

A

• Release of proinflammatory cytokines.
• Stimulation of hepatic acute phase reactants.
• Upregulation of endothelial adhesion molecules
promoting leukocyte migration.

37
Q

Anti-TNF-α Drugs – Adverse Effects?

A

• Suppression of Th1 activity ->
• Severe infections including invasive fungal disease.
• Reactivation of latent tuberculosis.
• Antibodies may develop against these biologics ->
• Elimination of clinical response to therapy.
• Acute or delayed infusion reactions.
• Increased risks of lymphoma, acute hepatic failure and congestive heart failure have also been
reported.

38
Q

Overview of Anti-integrins?

A

• Natalizumab
• Humanized monoclonal antibody targeting several
integrins on circulating inflammatory cells.
• Disruption of leukocyte vascular wall adhesion and
subsequent tissue migration.
• Indicated in moderate to severe, unresponsive
Crohn’s disease.

39
Q

Anti-integrins AE?

A 
• Infusion reactions
• Opportunistic infections
• Reactivation of the human polyomavirus (JC virus)
resulting in progressive multifocal
leukoencephalopathy.
40
Q

Define Exocrine Pancreatic insufficiency, causes, and clinical features?

A

When secretion of pancreatic enzymes
falls below 10% of normal, fat and protein
digestion is impaired.

CAUSED BY
• Cystic fibrosis
• Chronic pancreatitis
• Pancreatic resection
CLINICAL FEATURES
• Steatorrhea
• ADEK vitamin malabsorption syndromes
• Weight loss
41
Q

Pancreatic enzyme Supplementation overview and AE?

A

• Pancrelipase – combination of amylase, lipase, and proteases which are rapidly degraded by gastric acids.
• Enteric-coated formulations should be used or non- coated forms given with acid suppression therapy.
• Given by mouth with each meal.
• Adverse effects - diarrhea, abdominal pain.
Rarely; hyperuricosuria, renal stones and colonic
strictures.

Pharmacology (49 decks)

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