Laxatives & Purgatives

Introduction & terminology

• Laxatives — drugs that promote evacuation of the bowels — an umbrella term whose synonyms (aperients, purgatives, cathartics, evacuants) are used interchangeably but carry a graded distinction.
• Laxative vs purgative — a laxative/aperient gives milder action with soft but formed stool (laxation); a purgative/cathartic gives stronger, more fluid/forceful evacuation (catharsis). The distinction is dose-dependent — many drugs are a laxative in low dose and a purgative in higher dose.
• Physiological basis — laxation = evacuation of formed faecal material from the rectum; catharsis = evacuation of unformed, watery material from the entire colon. Most clinical agents promote laxation.
• Clinical relevance — constipation is a symptom, not a disease — worldwide adult prevalence ≈ 15 %, 2.4× more common in women, rising with age; the topic also anchors GI water-flux pharmacology contrasted with antidiarrhoeals.