Drugs for constipation Flashcards
List SEVEN major groups of drugs used to treat constipation.
(1) Bulk-Forming Laxatives
(2) Stool Surfactant Agents
(3) Osmotic Laxatives
(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; and (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
bulk-forming laxatives MOA
- Indigestible, hydrophilic colloids (fibre) -> absorb water and form bulk, emollient gel -> distends colon (increases stool mass)
- Promotes peristalsis
bulk-forming laxatives adverse effects
- bacterial digestion of plant fibres within the colon -> lead to flatus, bloating and abdominal pain
- avoid if an obstruction is suspected
- interaction with the absorption of other drugs
stool surfactant agents examples
DOCUSATE (oral), Mineral oil(oral), glycerin
stool surfactant agents MOA
- lower surface tension -> allow water/ lipids to penetrate stool
- mineral oil: lubricate + prevent water absorption from stool
mineral oil adverse effects
- not palatable
- aspiration can cause lipid pneumonitis (aspiration pneumonia)
- long term -> impair absorption of fat soluble vitamins (A,D,E,K)
examples of (1) sugar, (2) salt, and (3) balanced osmotic laxatives.
(1) Nonabsorbable Sugars: Sorbitol, LACTULOSE
(2) Nonabsorbable Salts: Magnesium hydroxide (milk of magnesia); Magnesium citrate; Sodium phosphate
(3) Balanced: Balanced Polyethylene Glycol (PEG)
* Balanced, isotonic solution of osmotically active sugar (PEG) and various salts
osmotic laxatives MOA
- Osmotically-mediated water movement into the bowel increases stool liquidity (softer stool) and volume
- Increased volume stimulates peristalsis
- High doses can produce bowel evacuation (purgation) within 1 to 3 hours
osmotic laxatives adverse effects
- colon bacteria act on sugars - FLATUS & ABDOMINAL CRAMPS
- must maintain adequate hydration
*PEG does not produce significant cramps/ flatus
stimulant laxatives examples
(1) Natural product, Anthraquinone Derivatives:
- Aloe, Senna and Cascara (oral or per rectum)
(2) Synthetic, Diphenylmethane Derivatives
- Bisacodyl (oral or per rectum)
- Used in conjunction with PEG for colonic cleansing prior to colonoscopy
stimulant laxatives MOA
- produce migrating colonic contractions
- stimulate enteric NS
- colonic electrolyte and fluid secretion
stimulant laxatives adverse effects
- anthraquinone derivatives -> chronic use cause BROWN PIGMENTATION of colon
laxatives comparison
bulk laxatives
- soft stool in 1-3 days
stimulant laxatives
- soft stool in 6-8hr
osmotic laxatives, PEG, suppositories (bisacodyl)
- watery stool in 1-3hr
chloride channel activators examples
- LUBIPROSTONE
*50% of patients have bowel movement within 24hrs of first dose
chloride channel activators MOA
- Stimulates type 2 chloride channels (ClC-2) in the small intestine
- Increases chloride-rich fluid secretions
- stimulate motility, shorten intestinal transit time
chloride channel activators adverse effects
- return of constipation after discontinuation
- AVOID in pregnancy
- nausea due to delayed gastric emptying
lubiprostone indications (3)
- chronic idiopathic constipation
- irritable bowel syndrome with constipation
- constipation caused by opioid medications (other than diphenylheptane opioids e.g., methadone) in people with ongoing pain due to medical conditions other than cancer
opioid receptor antagonists examples
- METHYLNALTREXONE
- subcutaneous every 2 days
methylnatrexone indications
- OPIOID INDUCED constipation in patients receiving palliative care
methylnatrexone MOA
- block intestinal mu (u) opioid receptors
does methylnatrexone block CNS analgesic effects?
NO. does not cross BBB
methylnatrexone adverse effects
common:
- stomach/ abdominal pain, nausea, diarrhea, flatulence, sweating
serotonin 5-HT4 receptor agonist examples
PRUCALOPRIDE, cisapride
serotonin 5-HT4 receptor agonist MOA
- stimulate 5-HT4 receptors on nerve terminals in GI wall -> increase neurotransmitter release & smooth muscle activity
- prokinetic effect -> promote GI motility
5HT4 agonist indication
- Chronic idiopathic constipation.
- Constipation refractory to treatment with other laxatives
5HT4 receptor agonist contradindication
INTESTINAL OBSTRUCTION
5HT4 agonist adverse effects
- stomach pain, nausea, dizzy, headache, diarrhea
cisapride
- adverse CARDIOVASCULAR event due to action at hERG K+ channel
