constipation Flashcards
what are the 7 classes of drugs used to treat constipation
physical:
(1) Bulk-Forming Laxatives
(2) Stool Surfactant Agents
(3) Osmotic Laxatives
physiological:
(4) Stimulant Laxatives
(5) Chloride Channel Activators
(6) Opioid Receptor Antagonists
(7) Serotonin 5-HT4-Receptor Agonists
Name examples of bulk-forming laxatives that are (1) natural plant products/fibres
(2) Semi-synthetic plant fibres
(3) Synthetic fibres
Examples of bulk-forming laxatives that are:
(1) Natural plant products/fibres: Psyllium, Sterculia, Agar, Bran
(2) Semi-synthetic plant fibres: Methylcellulose
(3) Synthetic fibres: Polycarbophil
what is the MOA of bulk forming agents
absorbs water to form bulk, emollient gel distends colon to increase stool mass - promoting peristalsis
what are the side effects associated with bulk forming agents
to administer with plenty of water
do not use within 2h of other drugs
what are examples of stool softeners?
enema - glycerin + nacl
oral - mineral oil
what is the MOA of stool softeners?
lowers surface tension, oil lubricates and slows down water absorption from stool
what are the adverse effects associated with mineral oil use?
not palatable - mix w fruit juice
aspiration - aspiration pneumonia
long term use can impair vitamin absorption (a,d,e,k)
List examples of (1) Nonabsorbable sugar, (2) Nonabsorbable salt, and (3) balanced osmotic laxatives.
Examples of osmotic laxatives:
(1) Sugars: Sorbitol, lactulose
(2) Salts: Magnesium hydroxide (milk of magnesia); Magnesium citrate; Sodium phosphate
(3) Balanced: Balanced Polyethylene Glycol (PEG), macrogol
what is the MOA of osmotic laxatives?
water movmment increases stool liquidity and volume - stimulating peristalsis
High doses can produce bowel evacuation (purgation) within 1 to 3 hours
What is the most impt advice for a patient when prescribed an osmotic laxative?
maintain adequate hydration by increasing oral fluid intake
what are the adverse effects associated with osmotic laxatives?
abdo cramps and flatus
serious: cardiac arrhythmias or acute renal failure
sodium phosphate can cause hyperphosphataemia, hypernatraemia, hypocalcemia, hypokalaemia
who should avoid osmotic laxatives?
should be avoided in elderly, patient on diuretics or have renal insufficiency or cardiac disease
what are examples of stimulant laxatives?
Anthraquinone Derivatives: senna, cascara (oral/rectal)
Diphenylmethane Derivatives: bisacodyl (tablet/rectal)
what is the MOA of stimulant laxatives?
migrating colonic contractions
what are some adverse effects associated with stimulant laxatives?
patients who are bed bound may require long term use
use of senna - brown pigmentation of stool
name an example of a chloride channel activator
lubiprostone
what are the adverse effects associated with lubiprostone
may return to constipation once discontinued
nausea
who should avoid using lubiprostone
pregnant women
name an example of an opioid receptor antagonist
methylnaltrexone bromide
when should opioid receptor antagonists be used?
only for opioid-induced constipation
what are the side effects of opioid receptor antagonists?
abdo pain
nausea
diarrhoea
sweating
rare: GI perforation
name an example of 5 HT4 receptor agonist
prucalopride
when should prucalopride not be used?
in the event of intestinal obstruction
what are adverse side effects associated with prucalopride?
abdo pain
nausea/diarrhoea
dizziness
