constipation and diarrhea

Question 1

bulk forming laxatives

Answer 1

methylcellulose, calcium poycarbophil, psyllium
MOA: facilitate holding water inside the colon to stimulate peristalsis (12-72 hours)
1st line constipation tx
AE: gas, cramps, esophageal obstruction, intestinal obstruction, allergic rxn
separate from other drugs by 2 hours
note: take with lots of water!

Question 2

emollient laxatives/stool softeners

Answer 2

docusate
surfactants that allow fat and water to mix (24-72 hours)
used to prevent constipation- not tx it
useful in pregnant and cardiac patients
often combined with stiumulant for tx of constipation

Question 3

lubricant laxatives

Answer 3

mineral oil
lubricates intestines and prevent water absorption (6-8 hrs)
AE: aspiration pneumonitis, anal leakage,
DI: malabsorption of vitamins and other meds- dont take with stool softener
note: patient needs to sit up to take meds to avoid lung aspiration

Question 4

saline laxatives

Answer 4

magnesium citrate, sodium phosphate
draw water into intestinal lumen via osmotic pressure (30-180 mins)
used before surgeries until poop is clear!
AE: can accumulate in renal dysfxn, dehydration from diarrhea, increased sodium absorption

Question 5

stimulant laxatives

Answer 5

senna, bisacodyl, castor oil
increases peristalsis (6-12 hours)
prevents opiate induced constipation- used with stool softener
used if bulk-forming agents fail
AE: cramps, senna causes urine discoloration, castor oil could induce labor
Interactions: drugs that increase pH can cause irritation
Note: dont use in pregnancy or for longer than 7 days- dont crush tabs

Question 6

hyperosmotic laxatives

Answer 6

PEG
draw water into the intestinal lumen via osmotic pressure (1-3 days)
used in children and infants to treat constipation
-can be used rectally (glycerin supp- 30min)

Question 7

stimulant rectal laxatives

Answer 7

bsacodyl suppositories
increases peristalis (15-60 mins)
AE: cramping
don’t take more than 7 days

Question 8

carbon dioxide releasing suppositories

Answer 8

sodium bicarb and potassium bitartrate
CO2 gas is formed expelling feces (5-30 mins)
last line
AE: pain when gas is expanding

Question 9

saline rectal laxatives

Answer 9

sodium phosphate
draw water into intestinal lumen via osmotic pressure (30 min)
used when most therapies fail
phosphate can accumulate

Question 10

enemas

Answer 10

water, saline, mineral oil, soap-suds
severe constipation that has failed other tx
AE: rectal damage

Question 11

loperamide

Answer 11

stimulates mu opioid receptors in intestines, slows motility, and decreases secretions (few hours onset)
1st line, but dont use in kiddies < 6
dont use in infectious or IBD
AE: dizzy and drowsy, toxic megacolon

Question 12

bismuth subsalicylate

Answer 12

forms bismuth oxychloride and salicylic acid in stomach-bismuth absorbent and antimicrobial- SA is antisecretory
not for use in PG or kids < 12, or ASA allergy
used in diarrhea and traveler’s (but not 1st line)
AE: tinnitus, black stools
interactions: warfarin, valproic acid

Question 13

diphenoxylate/atropine

Answer 13

stimulates mu opiod receptros in intestine, slowing motility, and decreasing secretions (few hours)
dont use in kids <2 or IBD
1st line for diarrhea symptoms
AE: dizzy, drowsy, euphoria, paralytic ileus, toxic megacolon

Question 14

octreotide

Answer 14

somatostatin analogue- # insuline, glucagon, vasoactive peptides, serotonin, motilin (few hours)
tx diarrhea associated with carcinoid tumors and vasoactive intestinal peptide tumors- also used to tx acromegaly and esophageal varices
AE: cholelithiasis, DM, hypothyroidism, cardiac dysfxn, malnutrition