Cathartics

Cathartics are substances that accelerate defecation and promote a relatively rapid and thorough evacuation of the bowels. The term derives from the Greek katharsis, meaning cleansing or purging. In medical usage, cathartics refer to agents that produce a stronger laxative effect than ordinary laxatives and are often associated with cramping and rapid stool passage. Historically, purgatives were described as the strongest form of bowel-cleansing agents.

Cathartics are generally categorized by their mechanism. Osmotic cathartics draw water into the intestinal lumen and include agents such as polyethylene glycol, lactulose, magnesium hydroxide, magnesium sulfate, and sodium phosphate. Stimulant or irritant cathartics increase intestinal motility and secretion and include senna, bisacodyl, and castor oil. Saline cathartics, which involve soluble salts that osmotically draw water into the colon, overlap with osmotic and laxative categories and have included magnesium citrate and similar preparations. Emollient laxatives such as docusate are typically not considered cathartics, as they soften stool rather than produce an evacuation.

Uses of cathartics include bowel cleansing prior to medical procedures such as colonoscopy and, in some cases, urgent relief of severe constipation. Their use is generally supervised by a clinician due to the potential for rapid fluid and electrolyte shifts. Adverse effects can include abdominal cramping, dehydration, and electrolyte disturbances; risks are heightened in individuals with kidney disease, congestive heart failure, GI obstruction, or inflammatory bowel disease.