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g per day), taking advantage of the meal‐related increase in colonic motor activity, and avoiding postponing defecation. Given the strong association of constipation in older people with medication use, medications should be eliminated or adjusted, substituting less‐constipating alternatives where possible. Medications used in the treatment of constipation are listed in Table 20.4.

Table 20.4 Medications used in the treatment of constipation.

Agent	Daily dose
Bulking agents
Bran (wheat or oat)	4–10 g
Psyllium	3–6 g
Calcium polycarbophil	2–4 g
Hydrolysed guar gum	3–6 g
Methylcellulose	2–4 g
Osmotic
Polyethylene glycol (PEG)	17–34 g
Lactulose	10–40 g
Magnesium salts	Generally avoided in elders
Sorbitol 70% solution	15–60 ml
Stimulant
Senna	15 mg
Bisacodyl	5–10 mg
Sodium picosulfate	5–10 mg
Other
Lubiprostone	8–24 μg b.i.d.
Linaclotide	290 μg
Prucalopride	1–2 mg
Methylnaltrexone	Weight‐based dosing
Probiotics	Bifidobacterium infantis 1 capsule, yoghurt 8–16 oz daily

      Pharmacological management

      Bulking agents

      Bulking agents commonly used include wheat or oat bran, psyllium (ispaghula), calcium polycarbophil, carboxymethylcellulose, and partially hydrolysed guar gum. A recent systematic review showed fibre supplementation to be beneficial in mild to moderate chronic constipation and in IBS.⁴³ Whilst taking fibre supplements, ensure that patients are drinking an adequate amount of water to avoid hard and bulky stools. In patients with faecal impaction, those who are bedbound, or with minimal fluid intake, fibre supplements should be avoided.⁴³ Side effects of fibre supplements include bloating and increased flatulence.

      Stool softeners

      Stool softeners such as dioctyl sodium sulfosuccinate and dioctyl calcium sulfosuccinate (docusate sodium) are reported to soften the stool, easing defecation. Despite the widespread use of these agents, there are no randomized controlled trials showing efficacy.⁴⁴ One study comparing dioctyl sodium sulfosuccinate with placebo showed no improvement in stool frequency or consistency.⁴⁵ Another study comparing dioctyl sodium sulfosuccinate with psyllium found psyllium to be superior.⁴⁶ The therapeutic use of stool softeners appears limited for the treatment of chronic constipation.

      Osmotic laxatives

Osmotic laxatives improve stool form and bowel movement frequency by increasing the amount of water retained in the lumen of the gut. Polyethylene glycol (PEG) (e.g. macrogol) and lactulose have therapeutic value in the treatment of constipation.⁴⁷ Other osmotic laxatives include sorbitol, magnesium salts, and saline salts. PEG, lactulose, and sorbitol have the greatest safety margins. Use of saline or magnesium salts comes with a risk for significant electrolyte disturbance, especially in older people. Elders with normal renal function may become hypermagnesemic with chronic use, especially at higher doses.⁴⁸ Magnesium salts should not be used in renal disease; and saline salts should be avoided in chronic renal failure, end‐stage liver disease, and heart failure. PEG appears to be the best tolerated overall in elders. Lactulose and sorbitol undergo bacterial metabolism in the gut, leading to increased symptoms of bloating, abdominal cramping, and flatulence in some patients and limiting their tolerability. A meta‐analysis of randomised controlled trials found osmotic laxatives to be superior to placebo in functional constipation.⁴⁹ Compared with placebo, PEG improves stool consistency and stool frequency. In comparative trials, PEG was superior to lactulose, showing improved efficacy and fewer side effects.⁵⁰ Trials also showed that PEG was non‐inferior to prucalopride (a prosecretory medication discussed below).⁵¹

      Stimulant laxatives

      Stimulant laxatives are widely used when osmotic laxatives have not had the desired effect. The adverse effects of stimulant laxatives in the treatment of constipation remain one of the most steadfast medical myths.⁸ Stimulant laxatives have been reported to damage the colon and cause laxative dependence. This perception may relate to the occurrence of melanosis coli, a dark‐brownish discoloration of the colon that occurs with long‐term use. The presence of melanosis coli has no functional significance. Prior studies reporting damage to the colonic enteric nerves and smooth muscle were anecdotal and uncontrolled. Many of these patients likely had pre‐existing abnormalities of the colon. When used at recommended doses, stimulant laxatives are unlikely to harm the colon.

      Stimulant laxatives result in abdominal discomfort and electrolyte imbalance in some patients.⁵² The most commonly available stimulant laxatives include senna, bisacodyl, and sodium picosulfate. Compared with placebo, bisacodyl 10 mg daily for 3 days increased stool frequency, improved stool form, and reduced straining in adults with constipation.⁵³ A comparison of bisacodyl with sodium picosulfate (uncontrolled) showed improvement with both in about three‐quarters of subjects.⁵⁴

      Secretagogues (prosecretory agents)

      Prosecretory agents can be used as second‐line treatment after standard laxative therapy. Currently, they include linaclotide, plecanatide, and lubiprostone. Lubiprostone selectively activates chloride C‐2 channels to increase intestinal fluid secretion. Lubiprostone does not affect colonic motility or sensation in humans. Patients reported more spontaneous bowel movements with lubiprostone than placebo (six versus four per week, p = 0.001), with the majority of patients experiencing a bowel movement within the first 24 hours.⁵⁵ The main side effect seen with lubiprostone was nausea. This effect is mitigated when the medication is taken with a meal and appears to be less problematic in elders.

      Linaclotide and plecanatide increase cyclic guanosine monophosphate, stimulating chloride and bicarbonate secretion. This increases salt and water secretion into the intestinal lumen and attenuates visceral afferent pain signalling, leading to improved stool consistency and frequency. Linaclotide is available

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