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. |
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