Senna is a laxative that works by irritating the bowel to stimulate bowel movement. As a laxative, it treats constipation but too much laxative can cause diarrhea. A benign but high-yield side effect is melanosis coli, which describes a black-brown discoloration of the colon.

Key Points

  • Senna
    • Mechanism
      • Stimulant laxative
        • Enteric nerve stimulation → colonic contraction
        • Works by irritating sensory nerve endings, which stimulates colonic motility and reduces colonic absorption
    • Clinical Use
      • Laxative for constipation
    • Adverse Effects
      • Diarrhea
      • Melanosis Coli
        • Harmless black coloration of colon, that may be observed on colonoscopy