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Palliative cancer care - constipation - Management
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Important aspects of prescribing information relevant to primary healthcare are covered in this section specifically for the drugs recommended in this CKS topic. For further information on contraindications, cautions, drug interactions, and adverse effects, see the electronic Medicines Compendium (eMC) (http://emc.medicines.org.uk), or the British National Formulary (BNF) (www.bnf.org).

What doses of laxatives may be needed in palliative care?

Table 1. Laxative doses that may be needed to manage constipation in palliative care.
Laxative
Licensed dose (adults)
Dose that may be needed in palliative care (off licence)
Bisacodyl
(tablets)
5–10 mg at night
20 mg three times a day
Bisacodyl
(suppositories)
10 mg daily
20 mg daily
Co-danthramer Strong
(dantron/poloxamer 37.5/500 mg capsules or 75/1000 mg suspension)
1–2 capsules (or 5 mL only) at night
3 capsules three times a day (or 10 mL twice a day)
Co-danthrusate
(dantron/docusate 50/60 mg capsules or suspension)
1–3 capsules (or 5–15 mL) at night
3 capsules twice a day (or 15 mL twice a day)
Docusate
(capsules or solution)
500 mg per day
200 mg three times a day
Lactulose
(syrup)
15 mL twice a day, adjusted according to patient's needs.
Use maximum licensed dose
Macrogol 3350 + electrolytes
(Movicol® sachets)
For constipation: 1–3 sachets per day.
For high faecal loading/impaction: 8 sachets dissolved in 1 Litre of water and drunk within 6 hours. Limit to 2 sachets (250 mL/hour) in heart failure.
Use maximum licensed dose
Macrogol 4000
(Idrolax® sachets)
1–2 sachets per day
Use maximum licensed dose
Senna
(tablets or syrup)
15 mg at night or 15 mg twice a day
15–22.5 mg (2–3 tablets) three times a day
Sodium picosulfate
(capsules or syrup)
5–10 mg at night
30 mg per day
Data from: [Regnard et al, 2004; BNF 54, 2007; Twycross and Wilcock, 2007]
Basis for recommendation
  • There is consensus between experts that the dose of laxatives should be titrated upwards until constipation is effectively controlled. This means that much higher doses and more frequent dosing than those specified on the product licence are often required to manage constipation (particularly opioid-induced constipation) effectively [Fallon and O'Neill, 1997; Twycross and Wilcock, 2007].

How do different types of laxatives work?

  • Bulk-forming laxatives (ispaghula husk, methylcellulose, and sterculia) act by retaining fluid within the stool and increasing faecal mass, leading to stimulation of peristalsis. They also have stool-softening properties.
  • Osmotic laxatives (e.g. lactulose, macrogols, phosphate enemas, and sodium citrate enemas) act by increasing the amount of fluid in the large bowel, by retaining fluid in the bowel, and by drawing fluid from the body into the bowel. Fluid accumulation in the lower bowel produces distension, leading to stimulation of peristalsis. Lactulose and macrogols also have stool-softening properties.
  • Stimulant laxatives cause peristalsis by stimulating colonic nerves (senna) or colonic and rectal nerves (bisacodyl, sodium picosulfate).
    • Senna is hydrolyzed to the active metabolite by bacterial enzymes in the large bowel.
    • Bisacodyl and sodium picosulfate are hydrolyzed to the same active metabolite. However, bisacodyl is hydrolyzed by intestinal enzymes, whilst sodium picosulfate relies on colonic bacteria.
  • Surface-wetting agents (docusate and poloxamer [an active ingredient of co-danthramer]) reduce the surface tension of the stool, allowing water to penetrate and soften it. Docusate also has a relatively weak stimulant effect.
  • Glycerol suppositories act as a lubricant, and have a weak stimulant action (probably due to an irritant effect).
  • Arachis oil enemas lubricate and soften faeces, thereby promoting a bowel movement. Bulk laxatives, osmotic laxatives, and docusate also have softening properties.

[Micromedex, 2007; Twycross and Wilcock, 2007]

What are the advantages and disadvantages of different laxatives?

  • The final choice of laxative will often depend on individual preference, and what has previously been tried.
Table 1. Advantages and disadvantages of different laxatives.
Laxative
Time to effect
Advantages
Disadvantages
Bulk forming laxatives
Ispaghula
(also known as psyllium)
2–3 days
Useful as a first-line choice in adults when it is difficult to get enough fibre in the diet.
Better tolerated than bran.
Must not be taken immediately before bed.
Adequate fluid intake is important, to prevent intestinal obstruction. This may be difficult for the frail or children.
Sterculia
Methylcellulose
2–3 days
As above.
As above.
Tablets swell in the mouth on contact with water, which may be disconcerting.
Wheat or oat bran
—
Can be added to food or fruit juice.
Can be given as bran bread or biscuits, but these are less effective than unprocessed bran.
May be unpalatable.
Often poorly tolerated (causes flatulence and bloating) unless increased slowly and can be difficult to take enough to be effective on its own.
Adequate fluid intake is important.
Osmotic laxatives
Lactulose
2–3 days
Palatable — although some find it sickly sweet.
Adequate fluid intake recommended.
Macrogols
(polyethylene glycol)
2–3 days
Licensed for use in faecal impaction.
Idrolax® does not contain electrolytes.
Movicol-Half® contains half the dose and electrolytes of Movicol®.
Some people find it difficult to drink the prescribed volume of macrogol.
Surface-wetting laxatives
Docusate sodium
1–2 days
Also has weak stimulant activity at higher doses.
May be a useful alternative for people who find it hard to increase their fluid intake.
—
Stimulant laxatives
Senna
8–12 hours
Rapid effect.
Licensed only for short-term use.
Syrup is unpalatable.
Sodium picosulfate
6–12 hours
Rapid effect.
Syrup is palatable.
Licensed only for short-term use.
Bisacodyl
6–12 hours
Rapid effect.
No syrup available.
Licensed only for short-term use.
Dantron
(terminal care only)
6–12 hours
Rapid effect.
Available only combined with a softener:
Co-danthramer (dantron with poloxamer).
Co-danthrusate (dantron with docusate).
Restricted to use in terminal care.
Concerns about possible carcinogenicity (from high-dose studies in rats).
People should be warned that it discolours urine red (occasionally blue or green).
Prolonged contact with the skin (e.g. faecal or urinary incontinence) can cause a dantron burn — an erythematous rash with a sharply demarcated border.
Rectal laxatives
All rectal laxatives
—
Easy to use if administered correctly.
Timing of effect may be more predictable than with oral laxatives.
Some people find them undignified and unpleasant to use.
All unlicensed for the treatment of faecal loading/impaction except Relaxit® micro-enema and Arachis oil retention enema.
Glycerol suppositories
(lubricating and weak stimulant)
15–30 minutes
Rapid effect.
Can be used for hard or soft stools.
Licensed for occasional use only.
Bisacodyl suppositories
(stimulant)
15–30 minutes
Rapid effect.
Use for soft stools.
Avoid if large, hard stools, as no softening effect.
Sodium phosphate and sodium bicarbonate suppositories (Carbalax®)
(effervescent)
30 minutes
Rapid effect.
People should be advised that these suppositories work by an effervescent action.
Docusate sodium enema
(softener and weak stimulant)
15–30 minutes
Rapid effect.
Can be used for hard or soft stools.
Correct administration important to prevent damage to rectal mucosa.
Sodium citrate enema (osmotic)
5–15 minutes
Rapid effect.
Smaller volume (5 mL) than a phosphate enema (130 mL).
Useful to remove hard, impacted stools.
Licensed for occasional use only.
Correct administration important to prevent damage to rectal mucosa.
Phosphate enema
(osmotic)
5 minutes
Rapid effect.
Useful to remove hard, impacted stools.
Licensed for occasional use only.
Correct administration important to prevent damage to rectal mucosa.
Arachis oil enema
(softener)
Retention enema — used overnight.
Useful for hard, impacted stools.
Licensed for occasional use only.
Should not be used in people with peanut allergy.
Not recommended
Liquid paraffin
(softener)
2–3 days
—
Adverse effects include anal seepage and irritation, malabsorption of fat-soluble vitamins, and (rarely) lipoid pneumonia.
Magnesium salts
(osmotic)
1–6 hours
Rapid effect
Not routinely recommended because their purgative action can be undesirably strong.
Data from the Electronic Medicines Compendium www.emc.medicines.org.uk.
Data from: [Sykes, 2004; Micromedex, 2007; Twycross and Wilcock, 2007]

How can I prevent or manage the adverse effects of laxatives?

  • Most adverse effects can be avoided or reduced by increasing the dose of oral laxatives gradually. Advise people to start at the lowest dose and, if necessary, increase it every few days until one or two soft, formed stools are produced each day. Common adverse effects include:
    • Bulk laxatives: flatulence and bloating.
    • Lactulose: flatulence, cramps, and bloating.
    • Macrogols: bloating, nausea.
    • Stimulant laxatives: abdominal cramps, diarrhoea.
  • Advise people taking bulk laxatives that an adequate fluid intake is important (to prevent intestinal obstruction) and that they should not be taken immediately before going to bed.
  • Advise people taking lactulose or macrogols that an adequate fluid intake is important because the drugs can be dehydrating.
  • The timing of stimulant laxatives can be particularly important for children and the frail or elderly, so that they provoke a single stool each day, at a time when the individual has adequate time to reach the toilet [Clayden et al, 2005]. Usually stimulant laxatives are given at bedtime, to produce a bowel movement the next morning. However, it may take a little experimentation to find the best time for an individual, especially if they naturally tend to defecate later in the day.
  • Avoid excessive doses of laxatives. This leads to diarrhoea and, if prolonged, electrolyte disturbances such as hypokalaemia. Excessive doses of bulk-forming laxatives, or inadequate fluid intake with bulk-forming laxatives, cause intestinal obstruction rather than diarrhoea.
  • If intestinal obstruction is suspected, do not use laxatives.
  • There have been concerns in the past that prolonged use of stimulant laxatives (off-licence use) might reduce colonic function or lead to tolerance. However, there is no convincing evidence that this is the case [Wald, 2006].

How can I prevent the adverse effects of rectal laxatives?

  • Suppositories must be placed alongside the bowel wall so that body heat causes them to dissolve and distribute around the rectum [Kyle, 2007].
  • Suppositories should be moistened before use to aid insertion.
  • Correct administration of enemas is important. Incorrect administration can injure the bowel wall, and occasionally even cause necrosis. After initial insertion of the enema nozzle, angle it towards the back before advancing further. Do not force insertion or administration [Bowers, 2006].
  • There have also been reports of hyperphosphataemia in people with chronic renal impairment following administration of phosphate enemas [Bowers, 2006].

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