Drug Action: How Bulk-forming Laxatives Work

Bulk-forming agents are often used as laxatives and are used mainly to treat constipation, when faeces are hard and painful to pass. Bulk-forming agents act on the intestine, causing faecal matter to retain water as it moves through the intestine. This makes faeces softer and easier to pass.

Before drug

Faecal matter does not retain much water as it passes slowly through the intestine, resulting in dry, hard faeces that are difficult to pass.

After drug

The bulk-forming agent mixes with faecal matter, causing it to retain water as it passes through the intestine. This produces faeces that are soft and bulky.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

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