Table 1.

Features of laxatives used in older adults

Bulk forming
  • Psyllium

  • Inulin

  • Guar gum

  • Calcium polycarbophil

  • 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

  • PEG 3350 without electrolytes

  • Lactulose

  • Glycerin suppositories

  • 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

    • -Lactulose by-products (1 tbsp has < 1.6 g galactose and < 1.2 g lactose) are not absorbed; however, encourage patients with diabetes to report any signs or symptoms of hyperglycemia

  • 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

  • Bisacodyl

  • Sennosides

  • 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

Unique mechanism of action
  • Prucalopride

  • Linaclotide

  • 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

  • PEG—polyethylene glycol.

  • Data from Kosar and Schuster.42