Can Olanzapine (olanzapine) cause constipation?

Olanzapine and Constipation

Yes, olanzapine can cause constipation as a common side effect, with constipation occurring in 9% of patients taking olanzapine compared to 3% in placebo groups. 1

Mechanism and Risk

• Olanzapine causes constipation primarily through its anticholinergic (antimuscarinic) effects, which can lead to decreased gastrointestinal motility 1
• Olanzapine has a moderate risk of causing constipation with a Report Odds Ratio (ROR) of 1.50 according to FDA Adverse Event Reporting System data 2
• Constipation is among the most common adverse effects reported with olanzapine, alongside somnolence, weight gain, dizziness, and dry mouth 3
• The anticholinergic properties of olanzapine affect multiple receptor types including muscarinic receptors (m1, m2, m3, m4), which play important roles in gastrointestinal function 4

Clinical Significance

• Constipation is specifically listed in the FDA label as one of the most common adverse reactions associated with olanzapine monotherapy, occurring in 9% of patients compared to 3% in placebo groups 1
• The FDA label specifically cautions about using olanzapine with caution in patients with constipation, paralytic ileus, or related conditions due to its anticholinergic effects 1
• While olanzapine-induced constipation is generally less severe than that seen with clozapine (which has an ROR of 1.61), it still requires monitoring and management 2, 5

Management Approach

• For patients on olanzapine experiencing constipation:

  • Increase fluid intake and encourage physical activity when appropriate 4
  • Increase dietary fiber if the patient has adequate fluid intake 4
  • Consider prophylactic laxatives for patients at high risk of constipation 4
  • For established constipation, stimulant laxatives such as bisacodyl 10-15 mg daily to three times daily can be used with a goal of one non-forced bowel movement every 1-2 days 4

• For persistent constipation:

  • Add osmotic laxatives such as polyethylene glycol (1 capful/8 oz water twice daily) 4
  • Consider adding other laxatives such as lactulose, magnesium hydroxide, or magnesium citrate if needed 4
  • In severe cases, consider adding a prokinetic agent such as metoclopramide 4

Special Considerations

• Patients with pre-existing gastrointestinal conditions may be at higher risk for developing constipation with olanzapine 1
• The anticholinergic burden may be increased when olanzapine is combined with other medications with anticholinergic properties 1
• Monitoring for constipation should be part of routine care for patients taking olanzapine, as patients may not always report this side effect 6
• In some cases, severe constipation can lead to complications such as bowel obstruction if left untreated, though this is more commonly associated with clozapine than olanzapine 6, 5

Comparison to Other Antipsychotics

• Olanzapine has a moderate risk of constipation (ROR = 1.50) compared to other atypical antipsychotics like clozapine (ROR = 1.61), quetiapine (ROR = 1.83), and paliperidone (ROR = 2.73) 2
• Risperidone appears to have the least effect on gastrointestinal function among atypical antipsychotics (ROR = 0.71) 2
• When constipation is a significant concern, considering an antipsychotic with lower anticholinergic properties may be appropriate 2, 6