Unprocessed wheat bran

When taken with food or fruit juice, this is an effective bulk forming preparation and can be helpful for many people. Oat bran can also be used. Finely ground bran can be given as bran bread or biscuits, but these are less effective than unprocessed bran. Bran should be introduced gradually to reduce symptoms of flatulence and bloating. Fluid intake should be increased. Continued long-term use is safe and may be regarded as a lifestyle change.

Bulk-forming preparations

Preparations such as ispaghula husk, methylcellulose and sterculia most closely copy the normal physiological mechanisms involved in bowel evacuation and are considered by many to be the laxatives of choice. They may be better tolerated than bran and are especially useful where patients have difficulty in increasing their intake of dietary fibre using fruit, vegetables and bran.

They work by swelling in the gut and increasing faecal mass so that peristalsis is stimulated. The laxative effect can take several days to develop. If tolerated and effective they can be used long-term but several cautions are required:

• The sodium content of some of these bulk laxatives (as sodium bicarbonate) should be considered in those requiring a restricted sodium intake (for example, in hypertension) 
• When recommending the use of a bulk-forming laxative, advise that an increase in fluid intake is necessary. In the form of granules or powder, the preparation should be mixed with a full glass of liquid (e.g. diluted fruit juice or water) before taking and ideally followed by a further glass of liquid. Fruit juice can mask the bland taste of these preparations 
• Intestinal obstruction is a rare complication resulting from inadequate fluid intake in patients taking bulk laxatives (and sometimes with unprocessed bran), particularly those whose gut is not functioning properly as a result of stimulant laxative abuse 
• Added bran and bulk-forming laxatives are usually considered unsuitable for opioid induced constipation as the problem relates to decreased gut motility. They may cause discomfort by distending or obstructing the bowel.

Osmotic laxatives

Macrogol and lactulose work by maintaining or increasing the volume of fluid in the bowel. They take several days to work. Lactulose is a liquid medicine; macrogol is available as sachets of powder that are dissolved in water before use. Lactitol is chemically related to lactulose and is also available as sachets. The contents of the sachet are sprinkled on food or taken with liquid. Lactulose and lactitol can cause flatulence, cramps and abdominal discomfort. Patients may want to tailor the dose to meet their needs and minimise side-effects. They can be used in the longer-term but bran or bulk-forming laxatives should usually be considered first-line for long-term use.

Epsom salts (magnesium sulphate)

Epsom salts is a traditional remedy that is no longer recommended but may still be requested by some older customers. It is an osmotic laxative that acts by drawing water into the gut and its action can be rapid. A dose usually produces a bowel movement within a few hours. Repeated use can lead to dehydration.

Glycerine suppositories

Glycerine suppositories have both osmotic and irritant effects and usually act within one hour. They are licensed for occasional use only and should not be regarded as a standard therapy. They may cause rectal discomfort. Moistening the suppository before use will make insertion easier. Some people find them undignified and unpleasant to use.

Stimulant laxatives

Stimulant laxatives such as senna and sennosides, bisacodyl and sodium picosulfate work by stimulating nerves in the colon and rectum, and increasing peristalsis. They are activated in the large bowel by the action of bacterial enzymes. They should only be considered if other laxatives (bulk-forming and osmotic) are ineffective. They are licensed exclusively for short-term use and generally should be used several times over a maximum period of one week. All stimulant laxatives can produce griping/cramping pains. The intensity of the laxative effect is related to the dose taken. It is advisable to start at the lower end of the recommended dosage range, increasing the dose if needed. They work within six to 12 hours when taken orally and are usually given at bedtime. Bisacodyl tablets are enteric coated and should be swallowed whole because the drug is irritant to the stomach. If bisacodyl is given as a suppository, the effect usually occurs within 15 minutes to one hour of insertion.

Docusate sodium

Docusate sodium has both stimulant and stool-softening effects and acts within several days. It can be prescribed for longer-term use and is started at a high dose and reduced according to the response.