How to manage lithium-induced constipation?

Management of Lithium-Induced Constipation

For lithium-induced constipation, a proactive approach with prophylactic laxatives is strongly recommended, starting with stimulant laxatives and osmotic agents like polyethylene glycol (PEG), along with lifestyle modifications. 1

Prevention Strategy

• Prophylactic laxatives should be prescribed for all patients taking lithium due to its high risk of causing constipation that can progress to serious complications 1
• Stimulant laxatives (senna, bisacodyl) should be initiated as first-line prophylactic treatment 1, 2
• Polyethylene glycol (PEG): 17g with 8 oz water twice daily is recommended as a preventive measure 1, 2
• Increase fluid intake and encourage physical activity when appropriate 2, 1
• Maintain adequate dietary fiber intake, though fiber supplements like Metamucil alone are unlikely to control medication-induced constipation 2

Treatment Algorithm for Established Constipation

First-line approach:

• Assess for cause and severity of constipation; rule out bowel obstruction 2
• Aim for one non-forced bowel movement every 1-2 days 2
• Titrate stimulant laxatives (senna, docusate, 2 tablets every morning; maximum 8-12 tablets per day) 2
• Increase laxative dose when increasing lithium dose 2

For persistent constipation:

• Add osmotic laxatives such as:
  • Polyethylene glycol (1 capful/8 oz water BID) 2
  • Magnesium hydroxide (30-60 mL daily) 2
  • Lactulose (30-60 mL daily) - CAUTION: may increase risk of lithium toxicity 3
  • Sorbitol (30 mL every 2 hours x 3 then as needed) 2

For severe or refractory cases:

• Consider adding a prokinetic agent (e.g., metoclopramide 10-20 mg PO QID) 2, 1
• Consider enemas (Fleet, saline or tap water) if oral treatments fail 2
• For severe cases, peripherally acting μ-opioid receptor antagonists like methylnaltrexone may be considered, though evidence is primarily from opioid-induced constipation 2

Important Considerations and Pitfalls

• Avoid using stool softeners alone without stimulant laxatives 1
• Exercise caution with lactulose as it may lead to dehydration and lithium toxicity 3
• Use magnesium salts cautiously in patients with renal impairment due to risk of hypermagnesemia 2
• Avoid bulk laxatives as primary therapy as they are unlikely to control medication-induced constipation and require adequate fluid intake 2
• Monitor for signs of lithium toxicity, especially in older patients or those with intercurrent illness that may affect hydration status 4
• Be vigilant about fluid balance as lithium can cause nephrogenic diabetes insipidus, which may complicate management of constipation 4

Special Considerations for Elderly Patients

• Ensure access to toilets, especially for patients with decreased mobility 2
• Optimize toileting schedule - educate patients to attempt defecation at least twice a day, usually 30 min after meals 2
• PEG (17 g/day) offers an efficacious and tolerable solution with good safety profile 2
• Avoid liquid paraffin for bed-bound patients due to risk of aspiration 2
• Monitor kidney function when using osmotic laxatives, especially in patients on diuretics 2