How to manage constipation in a 68-year-old black female with iron deficiency taking iron supplements (ferrous sulfate) daily?

Management of Constipation in a Patient Taking Iron Supplements

For a 68-year-old black female with constipation due to iron supplementation, initiate polyethylene glycol (PEG) 17g daily and consider alternate-day iron dosing to improve both constipation and iron absorption.

Understanding the Problem

Constipation is a common side effect of oral iron therapy, occurring in approximately 12% of patients taking iron supplements 1. In this case, the patient has not had a bowel movement for one week after starting daily iron supplementation, indicating significant constipation that requires prompt intervention.

Treatment Algorithm for Iron-Induced Constipation

First-Line Management:

1. Osmotic Laxative

   • Polyethylene glycol (PEG) 17g daily is the preferred first-line treatment
   • Generally produces a bowel movement within 1-3 days 2
   • Less likely to interact with iron absorption compared to stimulant laxatives

2. Stool Softener as Adjunct

   • Add docusate sodium 100mg twice daily
   • Works within 12-72 hours 3
   • Particularly important with iron supplementation to prevent complications like ileus 4

Optimize Iron Supplementation:

1. Modify Iron Dosing Schedule

   • Switch to alternate-day dosing rather than daily dosing
   • Recent evidence shows alternate-day dosing improves absorption and reduces side effects 5, 6
   • Take as a single morning dose rather than divided doses 6

2. Consider Iron Formulation

   • If using ferrous sulfate, maintain at 65mg elemental iron per dose
   • No more than 100mg elemental iron per day is recommended 1
   • Consider adding 500mg vitamin C with iron to enhance absorption 1

3. Timing of Administration

   • Take iron on an empty stomach if tolerated
   • Avoid taking with tea, coffee, or calcium (wait at least 1 hour) 1

Monitoring and Follow-up

1. Short-term Follow-up (1 week)

   • Assess bowel movement frequency and consistency
   • Evaluate for resolution of constipation
   • If no improvement, consider escalating to a stimulant laxative

2. Long-term Iron Therapy Management

   • Continue iron supplementation for 3 months after correction of anemia to replenish iron stores 1
   • Monitor hemoglobin at 3-4 weeks to assess response to iron therapy 7
   • Check iron parameters every 3 months for at least a year after correction 1

Common Pitfalls to Avoid

1. Overlooking the Underlying Cause

   • In a 68-year-old female, investigate the cause of iron deficiency
   • Consider gastrointestinal evaluation including upper and lower endoscopy 7

2. Inadequate Hydration

   • Ensure adequate fluid intake (at least 2L per day)
   • Dehydration can worsen both iron absorption and constipation

3. Continuing Daily Iron Despite Side Effects

   • Daily iron dosing increases hepcidin, which paradoxically reduces iron absorption 5
   • Alternate-day dosing may be both more effective and better tolerated

4. Focusing Only on Constipation

   • Address both the constipation and optimize iron therapy simultaneously
   • Poor adherence to iron therapy due to side effects can lead to inadequate treatment of anemia

If constipation persists despite these measures, consider switching to intravenous iron, which bypasses the gastrointestinal tract and eliminates constipation as a side effect 1.