What is the recommended treatment for constipation in an 18-year-old?

Treatment of Constipation in an 18-Year-Old

For an 18-year-old with constipation, the recommended first-line treatment is a trial of fiber supplementation, particularly psyllium, along with increased fluid intake, followed by polyethylene glycol (PEG) if fiber is insufficient. 1

Initial Approach

Lifestyle Modifications

• Increase fluid intake, especially for those with low fluid consumption, as those in the lowest quartile of fluid intake are more likely to be constipated 1
• Increase dietary fiber through unrefined breads, cereals, fruits, and vegetables 2
• Encourage physical activity when appropriate 1

First-Line Pharmacological Treatment

• Fiber supplementation:
  • Psyllium is recommended as the fiber supplement with the best supporting evidence 1
  • Dosage: 1 packet in 8 oz of liquid up to 3 times daily 3
  • New users should start with 1 dose per day and gradually increase to avoid bloating 3
  • Each dose should be taken with at least 8 ounces (full glass) of water 3

Second-Line Treatment

Osmotic Laxatives

• If fiber supplementation is insufficient, add polyethylene glycol (PEG) 1
• PEG dosing:
  • 17g dissolved in 4-8 ounces of beverage once daily 4
  • Ensure powder is fully dissolved before drinking 4
  • PEG has been shown to increase complete spontaneous bowel movements by 2.90 per week compared to placebo 1

Other Laxative Options

• Stimulant laxatives:
  • Bisacodyl 10-15 mg daily to three times daily with a goal of one non-forced bowel movement every 1-2 days 1
• Additional osmotic options:
  • Lactulose: 30-60 mL twice to four times daily 1, 5
  • Magnesium hydroxide: 30-60 mL daily to twice daily 1
  • Magnesium citrate: 8 oz daily 1

Treatment Algorithm

1. Assess for underlying causes:

   • Rule out medication-induced constipation (discontinue non-essential constipating medications) 1
   • Check for metabolic causes (hypercalcemia, hypokalemia, hypothyroidism, diabetes mellitus) 1

2. Initial treatment:

   • Start with fiber supplementation (preferably psyllium) and increased fluid intake 1, 6
   • Water supplementation (1.5-2.0 liters/day) significantly enhances the effect of high-fiber diet 6

3. If inadequate response to fiber:

   • Add PEG 17g daily 1
   • PEG can be used in combination with fiber for enhanced effect 1

4. For persistent constipation:

   • Add stimulant laxatives like bisacodyl 1
   • Consider other osmotic laxatives (lactulose, magnesium preparations) 1

Important Considerations

• Contrary to common belief, increasing fluid intake alone is not effective unless there is evidence of dehydration 7
• Not all dietary fibers are equally effective for constipation:
  • Water-insoluble fibers (cellulose, hemicellulose) are most effective for laxation 2
  • Water-soluble fibers (pectin, gums) have little effect on stool weight 2
• Side effects of fiber supplementation include flatulence 1
• Side effects of PEG include abdominal distension, loose stool, flatulence, and nausea 1
• Response to PEG has been shown to be durable over 6 months 1
• Stimulant laxatives at recommended doses are not harmful to the colon, contrary to popular belief 7

When to Consider Further Evaluation

• If constipation is refractory to available laxatives, evaluation for defecatory disorders and slow-transit constipation should be considered 8
• Persistent constipation despite adequate treatment may warrant referral to a gastroenterologist 8