Page 154 - phytochemistry I - PharmD Clinical

Mechanism of action of the laxative effect:

Anthraquinone glycosides are absorbed first in the small intestine
and hydrolysed in the colon by enzymes to give pharmacologically
active free aglycones.
The released anthraquinones irritate and stimulate the colon. They
exert their action by increasing the tone of the smooth muscle in the
wall of the colon and stimulate the secretion of water and
electrolytes into the large intestine (bulk laxatives).
This enhances the peristaltic movement leading to purgative effect.
They usually exert their action 8-12 hours after administration.
They usually cause spasm and gripping effect and administered
with carminative to counter act undesirable effects.

Precautions:

• Aloe latex should be avoided in children younger than 12 years and
used with caution for children older than 12 years. In addition,
anthraquinone glycoside may be secreted into breast milk; therefore
aloe and aloin should be avoided during lactation.

• Irritant/stimulant laxatives such as senna and cascara should be
used only for the treatment of acute constipation unable to be
treated with fiber.

• They are not recommended for long-term use. They both have a
high potential for dependence and abdominal discomfort side
effects.

• The use of senna in young children and infants has been associated
with severe diaper rash and blisters.

Side effects of chronic use of anthracene glycosides:

• Cathartic colon is a condition characterized by dilatation,
hypomotility and shortening of the right colon.

• Melanosis coli is a condition characterized by brown-black mucosal
pigment that has a polyhedral appearance.

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