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Source: Powell PH and Fleming VH. Diarrhea, Constipation, and Irritable Bowel Syndrome. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=7978775. Accessed April 29, 2012.

  • Functional constipation is bowel disorder characterized by difficult, infrequent, or seemingly incomplete defecation that does not meet criteria for irritable bowel syndrome (IBS).1

  • Constipation may be primary (occurs without underlying identifiable cause) or secondary (result of constipating drugs, lifestyle factors, or medical disorders).

  • Constipation is not a disease but symptom of underlying disease or problem.
  • Drugs that inhibit neurologic or muscular function of gastrointestinal (GI) tract, particularly colon, may result in constipation (Table 1).
    • All opiate derivatives associated with constipation to varying degrees.
    • Orally administered opiates appear to have greater inhibitory effect than parenterally administered agents.

Table 1. Drugs Causing Constipation

  • Prevalence in North America ranges from 12-19%.
  • More common in women and the elderly.

  • Increase dietary fiber
  • Initiate agents to soften stool when opiates are started.
  • Increase activity level.

  • Lack of activity
  • Lower socioeconomic status
  • Depression

Signs and Symptoms

  • Infrequent bowel movements
  • Stools that are hard, small, or dry
  • Difficulty or pain on defecation
  • Feeling of abdominal discomfort
  • Incomplete evacuation

Means of Confirmation and Diagnosis

  • History and physical examination to clarify what patient means by constipation. Ask specifically about alarm signs and symptoms:
    • Hematochezia
    • Melena
    • Family history of colon cancer
    • Family history of inflammatory bowel disease
    • Anemia
    • Weight loss
    • Anorexia
    • Nausea
    • Vomiting
    • Persistent constipation refractory to treatment
    • New onset or worsening constipation in elderly patients without evidence of primary cause
  • Rectal examination should be performed for presence of anatomical abnormalities, stricture, rectal mass, or fecal impaction.
  • Identify underlying secondary causes or conditions.

Laboratory Tests

  • No routine lab tests recommended.
  • Thyroid function studies, electrolytes, and blood glucose to determine presence of metabolic or endocrine disorders.
  • If alarm signs and symptoms present or when structural disease a possibility, select appropriate diagnostic studies:
    • Proctoscopy
    • Sigmoidoscopy
    • Colonoscopy
    • Barium enema

  • Relieve symptoms and restore normal bowel function.
  • Prevention of further episodes through alteration of lifestyle, particularly diet

  • General measures believed to be beneficial in managing constipation:
    • Dietary modification to increase amount of fiber consumed daily
    • Exercise
    • ...

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