Anti-constipation Flashcards
What are the drug classes for anti-constipation?
BOSSCO-5: Bulk-forming, osmotics, softener, stimulant, Cl channel activator, Opioid antagonist, 5-HT4 receptor agonist
Bulk-forming agents
Plant: psyllium, methylcellulose; synthetic: polycarbophil
MoA of bulk-forming agents
Hydrophillic colloid that absorbs water into lumen –> forms bulk/increase stool mass
SE of bulk-forming agents
Digestion of plant fibres leads to gas production and results in flatus, distension
Interferes with absorption of other drugs
Surfactant/softener
Docusate, mineral oil
MoA of surfactant
Decrease surface tension and increases H2O penetration into stools and make them softer
Also, mineral oil lubricates and prevents excessive H2O absorption from stool
SE of surfactants
Mineral oil: unpleasant taste, lipid pneumonitis with aspiration, impaired absorption of fat-soluble vitamins ADEK
Osmotic laxatives
Nonabsorbable sugars/salts (lactulose, sodium phosphate), balanced polyethylene glycol (PEG)
MoA of osmotics
Osmotically-mediated water movement into bowel to increase stool liquidity & volume
How fast do osmotic laxatives take to work
Highly effective — 1-3h
SE of Osmotics
Lactulose can cause flatus, abdominal cramps when digested by gut bacteria
Sodium phosphate can cause electrolyte abnormalities (hyperPO4,Na//hypoCa,K) that could cause arrhythmias, acute renal failure
Balanced PEG avoids electrolyte shifts, does not cause flatus
Precautions of osmotics
Due to electrolyte abnormalities caused by sodium phosphate, avoid in Px who have CVD, renal impairment, elderly
Stimulants
Anthraquinone derivatives: aloe
Diphenyl der.: Bisacodyl**
MoA of stimulant
Produce migrating colonic contraction by ENS stimulation, fluid secretion
What is bisacodyl usually combined with?
Bisacodyl + balanced PEG for colonic prep
SE of stimulants
Anthraquinone can cause brown discolouration of colon
Bisacodyl is safe for use
Cl channel activator
Lubiprostone
MoA of ClCA
Stimulates type 2 Cl- channels and increase Cl-rich secretion –> stimulates motility, decrease transit time
Contraindication of ClCA
Contraindicated in pregnancy
SE of ClCA
Return of constipation after discontinuation, delayed gastric emptying
Opioid antagonists
Methylnaltrexone (for opioid-induced constipation), alvimopan (post-op ileus)
MoA of opioid antagonist
Blocks intestinal MOR –> ensures normal GI motility
Additionally, these don’t cross BBB –> analgesic effect of opioids not affected
SE of opioid antagonist
Risk of CV toxicity with alvimopan use — only use short-term
5-HT4 agonist
Prucalopride, cisapride
MoA of 5-HT4 agonist
Stimulate 5-HT4 receptor on submucosal intrinsic primary afferent neurons (IPAN) terminals –> enhance release of NT —> stimulate enteric neurons to promote peristaltic reflex & colonic mass movement
SE of 5-HT4 agonist
Prucalopride: high affinity agonist — low risk of significant CVS effect
Cisapride: partial agonist —risk of adverse CV events
