Bulk forming laxatives are very good as first line agents for constipation. Bulk forming laxatives must not be used if there is bowel obstruction or if faecal matter is impacted. It is very important to drink plenty of water with these medicines. Results may be delayed up to 48 hours.
Bulk forming laxatives with bowel stimulants should generally be used only in the short-term and then changed to a standard bulk forming laxative if advised by your doctor.
Bulk forming laxatives include Granocol (with caution in diabetes), Metamucil (with caution in diabetes), Mucilax (sugar-free is available), Normafibe (with caution in diabetes), and Normacol Plus. Granocol and Normacol Plus contain the bowel stimulant frangula and should not be used during pregnancy, unless under medical supervision.
Osmotic laxatives such as lactulose (Actilax, Duphalac and Lac-Dol) must be taken regularly for full effect, and should be used cautiously in the elderly if there are likely to be electrolyte imbalances. Action may be delayed up to 48 hours.
Stimulant laxatives such as bisacodyl (Durolax) and senna (Senokot, Coloxyl with Senna and Sennesoft) may be required when constipation is severe and a rapid effect is required. They should not be used regularly unless under medical supervision.
The onset of action is about 8 hours. After complete evacuation of the bowel by a stimulant laxative, it may take 2 to 3 days for faecal matter to collect in the bowel again, and so taking a stimulant laxative every night is not usually necessary.
Stimulant laxatives should not be used during pregnancy.
Psyllium husks and herbal laxatives may also help in the relief of constipation.
Last Reviewed: 11 July 2001