Constipation

Question 1

classification of drugs for constipation/laxatives/purgatives

Answer 1

laxative - expel formed stool
purgatives - expel watery stool

bulk laxatives
stimulant/irritative laxatives
osmotic laxatives
stool softeners
chloride secretors
miscellaneous

Question 2

bulk laxatives / dietary fibres/ prebiotics

Answer 2

DOC for constipation (idiopathic/ pregnancy/ irritable bowel syndrome)

Psyllium (Metamucil)
Bran
Husk
Methyl cellulose
Ispaghula (Isabgol)

SE: increase bacterial growth (this prebiotics) which could lead to flatulence and increased ammonia which is absorbed into the blood

CI: paracytic ileus or megacolon

Question 3

Stimulant or irritant laxatives

Answer 3

Bisacodyl
Senna
Cascara
Prucalopride (stimulates 5HT4)
Castor oil
Phenopthalein

use: constipation resistant to bulk laxative (idiopathic and IBS)
paracytic ileus
bowel evacuation before surgery or abdominal x-ray

CI: pregnancy (could lead to abortion)
spastic colony (abdominal pain)

SE: melanosis coli caused by Senna (contains black anthrol pigment)

Question 4

Osmotic laxatives

Answer 4

saline purgatives (sodium phosphate)
non digestable sugars (mannitol,urea)
magnesium salts
poly ethylene glycol (DOC)
lactulose

DOC for whole bowel irrigation for colonoscopy/ before GIT surgery

Question 5

Lactulose

Answer 5

reduces ammonia absorption from colony
use : laxative of choice in liver failure (hepatic encephalopathy)

Question 6

hepatic encephalopathy

Answer 6

mild: lactulose (increase ammonia absorption)
severe: kill colonic bacteria
Rifaximin (overall DOC), Neomycin

Question 7

Stool softener

Answer 7

Doccusate (DOSS)
Paraffin wax
Mineral oil - SE: could lead to aspiration pneumonia and foreign body granuloma

use: pregnancy, hernia patient,after abdominal surgery

Question 8

Chloride secretors

Answer 8

Lubiprostone - PGE1 analogue - increase chlorine secretion
Linaclotide, Plecanatide - stimulates soluble guanylyl cyclase, stimulates CFTR - increase chlorine secretion

use: constipation in IBS

Question 9

Sodium secretor

Answer 9

Tenapanor - inhibitor of Na+ H+ antiporter

new drug for constipation in IBS

Question 10

laxative of choice in pregnancy

Answer 10

bulk laxatives > Doccusate

Question 11

laxative of choice in liver disease

Answer 11

Lactulose

Question 12

Miscellaneous laxatives and purgatives

Answer 12

Neostigmine - postoperative paracytic ileus

Erythromycin, Clarithromycin - stimulates motilin receptor - SE: hypertrophic pyloric stenosis

opioid induced constipation - Alvimopan