Causes of constipation in adults

Causes of constipation range from common dietary or lifestyle factors, to mechanical obstruction associated with pelvic floor dysfunction. Common factors that can contribute to constipation include:

  • medications (see Examples of drugs that commonly cause constipation for a list of drugs that commonly cause constipation)
  • inadequate dietary fibre
  • dehydration
  • inappropriate bowel habits (eg ignoring the urge to defecate)
  • inadequate physical activity (eg from decreased mobility)
  • change in environment (eg holiday, entry into residential aged-care facility)
  • painful anorectal disorders (eg haemorrhoids, anal fissures)
  • loss of muscle power caused by other medical conditions (eg chronic obstructive pulmonary disease).
Figure 1. Examples of drugs that commonly cause constipation
  • opioids
  • drugs with anticholinergic effects (eg oxybutynin, trihexyphenidyl [benzhexol], tricyclic antidepressants, clozapine, olanzapine, risperidone, quetiapine)
  • 5-HT3–receptor antagonists (eg ondansetron)
  • aluminium- and calcium-containing antacids
  • oral calcium supplements
  • oral iron supplements
  • verapamil
  • glucagon-like peptide-1 analogues (eg liraglutide, semaglutide).

Most of the factors contributing to constipation can be magnified or compounded in older patients, especially residents of aged-care facilities where factors such as lack of privacy and difficult access to toilet facilities are common. In older patients, prolonged constipation can lead to faecal impaction, causing urinary or faecal overflow incontinence. Constipation is common in patients with dementia or depression, and these patients may present with behavioural changes.