Page 34 - phytotherapy_ EBOOK_2025

1. Regulation of colonic motility – stimulating peristaltic movements while inhibiting local
segmental contractions, thereby speeding colonic transit and reducing fluid reabsorption.

2. Alteration of fluid and electrolyte balance – enhancing mucus production and active
chloride secretion, which leads to an increase in water content within the intestinal lumen.

Clinical pharmacology
The laxative effect of senna typically begins within 8–10 hours after administration;
therefore, it is generally recommended to be taken at bedtime. Sennosides, the active
constituents, enhance the natural colonic response to physiological stimuli such as food
intake and physical activity, without disturbing normal bowel function.
In patients with severe irritable bowel syndrome, sennosides effectively relieve
constipation. When used at therapeutic doses, they preserve normal defecation patterns
while softening the stool significantly. Sennosides also increase colonic motility and
transit rate, leading to higher fecal bulk and an increase in bacterial dry mass. Because
of their specific action on the colon, sennosides are minimally absorbed in the upper
gastrointestinal tract.
Toxicity
The primary symptoms of senna overdose include abdominal cramping and severe
diarrhea, which can lead to significant fluid and electrolyte depletion. Management is
supportive, emphasizing adequate fluid replacement. Electrolyte levels, particularly
potassium, should be carefully monitored, with special attention to children and elderly
patients, who are more susceptible to complications.
Contraindications
As with other stimulant laxatives, the use of this drug is contraindicated in individuals
with ileus, intestinal obstruction or stenosis, intestinal atony, unexplained abdominal
symptoms, inflammatory bowel diseases, appendicitis, or abdominal pain of unknown
origin. It should also be avoided in cases of severe dehydration accompanied by water
and electrolyte imbalance, as well as in chronic constipation. Senna leaves are not
recommended for use in children under 10 years of age.
Warnings
Stimulant laxatives should be avoided in the presence of abdominal pain, nausea, or
vomiting, as these symptoms may indicate an underlying disorder. Rectal bleeding or
absence of bowel movement following laxative use may signal a serious medical
condition that requires prompt evaluation.
Chronic misuse of stimulant laxatives, leading to persistent diarrhea and fluid-
electrolyte depletion, can cause dependence, necessitating progressively higher doses.
Prolonged use may also result in electrolyte imbalances such as hypokalaemia, atonic

33