Stimulant laxatives

Stimulant laxatives

Stimulant laxatives, also known as irritant cathartics, include:

• bisacodyl
• castor oil
• senna.

Pharmacokinetics

Stimulant laxatives are minimally absorbed and are metabolized in the liver. The metabolites are excreted in urine and stool.

Pharmacodynamics

Stimulant laxatives promote peristalsis and produce a bowel movement by irritating the intestinal mucosa or stimulating nerve endings of the intestinal smooth muscle.

No job is too small

Castor oil also increases peristalsis in the small intestine.

Pharmacotherapeutics

Stimulant laxatives are the preferred drugs for emptying the bowel before general surgery, sigmoidoscopic or proctoscopic procedures, and radiologic procedures such as barium studies of the GI tract.

They’re also used to treat constipation caused by prolonged bed rest, neurologic dysfunction of the colon, and constipating drugs such as opioids.

Drug interactions

No significant drug interactions occur with the stimulant laxatives. However, because these laxatives produce increased intestinal motility, they reduce the absorption of other oral drugs administered at the same time, especially sustained-release forms. 

Warning!

Adverse reactions to stimulant laxatives

Adverse reactions to stimulant laxatives include:

• weakness
• nausea
• abdominal cramps
• mild inflammation of the rectum and anus
• urine discoloration (with senna).