Constipation
Stepwise laxative management, opioid-induced constipation, and NICE guidance
Constipation is one of the most common gastrointestinal complaints in primary care, characterised by infrequent, difficult, or incomplete defecation. Management follows a stepwise approach from bulk-forming laxatives through osmotic agents to stimulants, with specialist options available for refractory or opioid-induced constipation.
Causes and Assessment
Constipation may be primary (idiopathic or functional) or secondary to drugs, diet, or systemic disease. Common drug causes include opioids, tricyclic antidepressants, anticholinergics, calcium channel blockers, and iron supplements. Systemic causes include hypothyroidism, hypercalcaemia, Parkinson's disease, and diabetes. Assessment includes history, digital rectal examination, and basic bloods (TSH, calcium). Alarm features — rectal bleeding, weight loss, new onset over 50, family history of colorectal cancer — require urgent investigation.
Pharmacological Management — Stepwise Approach
First-line treatment is a bulk-forming laxative: ispaghula husk (Fybogel) 1 sachet twice daily with adequate fluid. If ineffective after 2–3 days, an osmotic laxative is added: macrogol (Movicol) 1–3 sachets daily is preferred, or lactulose 15 mL twice daily (though lactulose causes more flatulence). Stimulant laxatives — senna 7.5–15 mg at night or bisacodyl 5–10 mg — are added if osmotic agents are insufficient. For faecal impaction, high-dose macrogol (8 sachets/day for up to 3 days) is recommended. Specialist options include prucalopride 2 mg once daily (NICE TA211) for chronic constipation unresponsive to two or more laxatives.
Opioid-Induced Constipation
Opioid-induced constipation (OIC) is caused by peripheral mu-opioid receptor activation in the gut. All patients starting regular opioids should receive a prophylactic stimulant laxative (senna or bisacodyl) — not a bulk-forming agent. If standard laxatives fail, peripherally acting mu-opioid receptor antagonists are available: naloxegol 25 mg once daily (NICE TA345) or methylnaltrexone subcutaneous injection — both reverse gut effects without reversing analgesia. Naldemedine 200 mcg daily is an alternative.