Gastrointestinal/Laxatives

Laxatives

also: senna · macrogol · lactulose · ispaghula · docusate · constipation

Overview

Laxatives by class — choosing depends on the cause (opioid constipation, faecal impaction, hepatic encephalopathy).

Mechanism

Bulk-forming (ispaghula) ↑stool mass; osmotic (macrogol, lactulose) draw water into the lumen; stimulant (senna, bisacodyl) ↑peristalsis; softeners (docusate) wet the stool.

Indications

Constipation
Faecal impaction
Bowel preparation
Hepatic encephalopathy (lactulose)

The agents

Bulk-forming (ispaghula husk)fibre

Need adequate fluid; avoid in obstruction/impaction.

Osmotic (macrogol, lactulose)draws water

Macrogol first-line (incl. children, impaction); lactulose also for hepatic encephalopathy.

Stimulant (senna, bisacodyl)↑peristalsis

Good for opioid-induced constipation (with a softener); avoid in obstruction.

Stool softener (docusate)softener

Naloxegol / methylnaltrexoneperipheral opioid-receptor antagonist

Opioid-induced constipation refractory to standard laxatives — blocks gut µ-receptors without reversing analgesia.

Adverse effects

Cramping, bloating, diarrhoeacommon

Electrolyte disturbance (overuse)common

Cautions & contraindications

Stimulant/bulk laxatives in intestinal obstructionall

Perforation risk.

Interactions

Monitoring & kinetics

Bowel habit; fluids

Oral / rectal. Opioid constipation: a stimulant + softener (osmotic alone often insufficient).

Source: NICE CKS — Constipation · BNF — Laxatives