Bulk forming
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Psyllium -
Inulin -
Guar gum -
Calcium polycarbophil
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Can be used for the prevention and treatment of constipation -
Onset of action: 12–72 h -
Available in multiple dosage forms (powders, wafers, chewable tablets, capsules) -
Might not aid constipation due to slow transit, pelvic floor dysfunction, or medication -
Must be taken with ≥ 250 mL water or juice to prevent fecal impaction and esophageal obstruction -
Avoid in patients with cognitive impairment, fluid restrictions, dehydration, dysphagia, or esophageal strictures, or in those who are bedridden -
Suggested to space by 2 h from all other medications
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Osmotic
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PEG 3350 and lactulose can be used for the prevention and treatment of constipation; glycerin suppositories can be used for the treatment of constipation -
Onset of action: PEG 3350 48–96 h; lactulose 24–48 h; glycerin 15–60 min -
Neither PEG 3350 nor lactulose is absorbed and both lack electrolytes; therefore, these are good options for patients with renal impairment, cardiac dysfunction, or diabetes
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Dose-dependent nausea, abdominal bloating, cramping, diarrhea, and flatulence can occur with both PEG 3350 and lactulose; however, PEG 3350 has a higher incidence of diarrhea in elderly patients but a lower incidence of flatulence -
Some find lactulose too sweet, but the taste can be masked by diluting it in water, fruit juice, milk, or desserts -
PEG 3350 is a tasteless, odourless powder that is dissolved in 250 mL of water, juice, coffee, or tea -
Lactulose is less expensive at starting doses (15 mL every night costs $13/mo) compared with PEG 3350 ($24/mo) -
Glycerin is less effective if stool is dry and hard
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Stimulant
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Can be used for the prevention and treatment of constipation -
Onset of action: 6–12 h -
Might provide benefit in neurogenic or slow-transit constipation -
Tolerance can occur with slow-transit constipation but it is rare -
Senna might discolour urine or feces yellow-brown or red-violet -
Side effects include abdominal pain and cramping
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Unique mechanism of action
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Have only been studied for the treatment of refractory constipation -
Onset of action: prucalopride 2–3 h; not reported for linaclotide (bowel movements reached maximal peak within first wk of use) -
Have only been evaluated against placebo so the exact role of these new agents is unknown -
Requires a prescription and might not be covered by provincial drug formularies (cost about $80/mo to $240/mo) -
Side effects include diarrhea, abdominal pain, and nausea
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