Lower GI pharm

Question 1

Drugs with constipation as a side effect

Answer 1

Ca channel blockers (verapamil), opioid analgesics, antimuscarinics, drugs with antimuscarinic side effects (TCADs, antipsychotics, 1st gen antihistamines, parkinsonian agents), Al and Ca-containing antacids, chemotherapeutic vinca alkaloids

Question 2

Primary use of laxatives

Answer 2

treatment of acute constipation

Question 3

Treatment of most simple constipation

Answer 3

high fiber diet, exercise (abs), adequate fluid intake

Question 4

First line for constipation

Answer 4

fiber/bulk-forming laxatives like psyllium (Metamucil)

Question 5

Psyllium mechanism of action

Answer 5

facilitate passage and stimulates peristalsis via absorption of water and subsequent bulk expansion

Question 6

Psyllium interactions

Answer 6

digoxin and salicylates

Question 7

preferred adjunct to fiber in treatment of constipation

Answer 7

saline (osmotically active agents) cathartics

Question 8

Mechanism of saline cathartics

Answer 8

nonabsorbable ions –> osmotic retention of water in intestine –> increased peristalsis

Question 9

Milk of Magnesia contraindications

Answer 9

renal dysfunction (can lead to increased Mg retention

Question 10

Use of phosphate enemas

Answer 10

fecal impaction

Question 11

Miralax use

Answer 11

difficult to treat constipation

prolonged use –> electrolyte depletion

Question 12

Lactulose mechanism

Answer 12

nondigestable sugar dissacharide –> metabolized by colonic bacteria to low molecular weight acid –> osmotic diarhea, increased colonic peristalsis

Question 13

Lactulose use

Answer 13

acute constipation in elderly patients

Question 14

Bisacodyl (Dulcolax) mechanism

Answer 14

activation of prostaglandin-cAMP and NO-cGMP pathways –> induced low-grade inflammation in bowel –> accumulation of water and electrolytes –> stimulation of peristalsis

Question 15

Bisacodyl ADRs

Answer 15

electrolyte/fluid deficiencies, severe cramping

most widely abused laxative

Question 16

Docusate mechanism

Answer 16

it is a surfactant –> stool softener (facilitates admixture of aqueous and fatty substances)

Question 17

Docusate use

Answer 17

prevention of constipation in combination with stimulant laxative (Bisacodyl) when initiating opioid analgesic therapy

Question 18

Glycerin suppositories use

Answer 18

initiate defecation reflex in neonates/peds

Question 19

Peripherally acting opioid antagonists

Answer 19

Methylnaltrexone, naloxegol

used for patients taking opioids for non-cancer pain that have failed laxative therapy

Question 20

Drugs associated with diarrhea

Answer 20

misoprostol, antibiotics (esp broad spec), muscarinic agonists, SSRIs, colchicine, NSAIDs, digoxin

Question 21

Management of sudden onset of diarrhea

Answer 21

usually self-limiting

Question 22

opioid antidiarrheals

Answer 22

diphenoxylate, loperimide

Question 23

Loperimide use

Answer 23

traveler’s diarrhea, cholera

should be discontinued if no improvement in 48h

Question 24

Polycarbophil (Mitrolan) mechanism

Answer 24

marked capacity to bind free fecal water

Question 25

Polycarbophil use

Answer 25

diarrhea (binds water) and constipation (prevents fecal dessication)

Question 26

bismuth subsalicylate (Pepto Bismol, Kaopectate) use

Answer 26

mild/moderate diarrhea (promotes formed stool)

Question 27

bismuth subsalicylate contraindications

Answer 27

Children under 12 (risk of Reye's syndrome)

Question 28

Probiotics mechanism

Answer 28

suppress growth of pathogenic organisms, restoring normal flora

Question 29

IBS pathophysiology

Answer 29

idiopathic, chronic, relapsing abd discomfort and altered GI motility

Question 30

Treatment of IBS

Answer 30

low dose TCADs for abd pain/discomfort antidiarrheals/fiber/laxatives for improving bowel function Agents specific for IBS: 5-HT3 antagonists (Alosetron), 5-HT4 agonists (Tegaserod)

Question 31

Alosetron mechanism

Answer 31

blocks 5-HT3 receptors on sensory/motor neurons --> reduced pain and inhibits colonic motility

Question 32

Alosetron use

Answer 32

Only in severe IBS in women with diarrhea as the prominent symptom, unresponsive to conventional therapy

Question 33

Alosetron ADRs

Answer 33

constipation, ischemic colitis (1/3000)

Question 34

Tegaserod mechanism

Answer 34

5-HT4 agonist --> release of neurotransmitters for peristaltic reflex --> gastric emptying and intestinal motility

Question 35

Tegaserod contraindications

Answer 35

renal or hepatic dysfunction

Question 36

Tegaserod use

Answer 36

women under 55 with IBS and predominant constipation; chronic idiopathic constipation that is unresponsive to other treatments

Question 37

Tegaserod ADRs

Answer 37

linked with heart attacks, strokes, unstable angina