Unprocessed wheat bran, taken with food or fruit juice, 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, and fluid intake should be increased. Continued long-term use is safe and may be regarded as a change in lifestyle.

Bulk-forming preparations such as ispaghula husk, methylcellulose and sterculia are those that 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, bulk forming preparations can be used long-term. However, 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 laxative, it is important to advise that an increase in fluid intake is necessary.

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 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.

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.

Stimulants laxatives, such as senna and sennosides, bisacodyl and sodium picosulfate, work by stimulating nerves in the colon and rectum and increasing peristalsis. They should only be considered if bulk-forming and osmotic laxatives are ineffective. They are only licensed for short-term use and generally should be used several times over a maximum of one week. It is advisable to start at the lower end of the recommended dosage range, increasing the dose if needed.

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