constipation drugs

Question 1

Bulk Laxatives

Psyllium (Metamucil)
Methylcellulose

Answer 1

Non-soluble vegetable fibers + cellulose derivatives –> absorb water and increases fecal mass, bulk, softness, and stool frequency

Take with lots of water

AE: bloating, flatulance

Question 2

Emollients

Docusate

Answer 2

Decreases surface tension of stool, easier for water to enter, softens stool

AE: abdominal cramps

May contain sugars, monitor in diabetics

Question 3

Lubricant

Mineral oil

Answer 3

Coats stools and prevents absorption of fecal water into colon –> stool softening + easy passage

Use for constipation in patients who need to avoid straining (post-op)

AE: prevent absorption of other nutrients, water, and drugs

Question 4

Polyethylene Glycol

Answer 4

Miralax (for constipation), GoLytely (bowel prep)

Osmotic laxative - draws water into colon + stool

AE: bloating, cramping, flatulance

Question 5

Saline (“salts”)

Mg Citrate
Mg Hydroxide
Sodium phosphate

Answer 5

Osmotic laxative - draws water into colon + stool

Used for bowel prep

AE: confusion, dizziness, muscle cramps, arrhythmia, electrolyte imbalances

BLACK BOX: Na phosphate - acute phosphate nephropathy

Don’t use with heart/renal failure patients

Question 6

Sugars

Lactulose
Sorbitol

Answer 6

Osmotic laxative - draws water into colon + stool

Use: constipation + hepatic encephalopathy

AE: cramps, flatulance, diarrhea

Question 7

Stimulant Laxatives

Bisacodyl (Ducolax)
Senna

Answer 7

Stimulates myenteric plexus - directly increases colonic motility

Most effective but side effects; used in bowel prep for endoscopy/colonoscopy

AE: abdominal pain, cramping, N/V, electrolyte imbalance, decreases effects of coumadin

Can cause melanosis coli - discoloration of colon

Once stopped - rebound constipation

Question 8

Lubiprostone

Answer 8

Locally activates minor Cl- channels –> promotes intraluminal motility

Use: severe refractory constipation

AE: nausea

Expensive

Question 9

Linaclotide

Answer 9

Activates guanylate cyclase-C receptor –> increases fluid secretion into lumen

Use: IBS-C

AE: diarrhea

Question 10

Plecanatide

Answer 10

Activates guanylate cyclase-C receptor –> increases fluid secretion into lumen

Use: chronic idiopathic constipation

AE: severe dehydration (avoid in kids)