Constipation

Question 1

What is constipation?

Answer 1

Definition: Difficult or infrequent passage of stool, often with straining or feeling of incomplete evacuation. Chronic if symptoms last ≥3 months.

Question 2

What drug classes are used to treat constipation, with examples?

Answer 2

1. Bulk-Forming Agents: Psyllium, methylcellulose, polycarbophil.
2. Osmotic Laxatives:
   · PEG 3350 (first-line, A recommendation)
   · Lactulose, sorbitol
   · Magnesium salts (hydroxide, citrate) – avoid in renal impairment.
3. Stimulant Laxatives:
   · Bisacodyl, senna (short-term/intermittent use).
4. Stool Softeners: Docusate (limited evidence).
5. Secretagogues:
   · Lubiprostone (chloride channel activator)
   · Linaclotide (guanylate cyclase-C agonist) – for chronic idiopathic constipation & IBS-C.
6. Opioid Antagonists (for OIC):
   · Methylnaltrexone, naloxegol, alvimopan (peripheral µ-receptor blockers).

Question 3

what are its primary and secondary causes of constipation?

Answer 3

· Primary (Idiopathic) Causes:
· Normal transit (functional)
· Slow transit
· Pelvic floor dysfunction/disordered defecation
· Secondary Causes:
· Drugs: Opioids, anticholinergics, calcium channel blockers, NSAIDs, iron, antacids (Al/Ca).
· Medical Conditions: IBS, hypothyroidism, diabetes, neurological disorders, colorectal disorders.
· Lifestyle: Low fiber, inadequate fluids, inactivity, ignoring urge.

Question 4

What are the pathophysiologic mechanisms of constipation?

Answer 4

· Normal Transit Constipation: Most common; normal motility but hard stools, bloating, difficulty evacuating.
· Slow Transit Constipation: Delayed colonic transit → infrequent stools.
· Pelvic Floor Dysfunction: Impaired coordination of pelvic muscles/anal sphincter → difficulty expelling stool.
· Secondary Mechanisms:
· Opioids → spastic nonpropulsive contractions, ↑ anal tone.
· Anticholinergics → reduced gut motility.
· Low fiber/fluid → reduced stool bulk & dryness.

Question 5

What are the goals of treating constipation?

Answer 5

· Short-term: Relieve acute symptoms, restore normal bowel function.
· Long-term: Prevent recurrence, reduce laxative dependence, improve quality of life.
· Correct underlying causes where possible (e.g., adjust medications, treat hypothyroidism).
· Educate on diet, lifestyle, and appropriate laxative use.

Question 6

What non-drug strategies are recommended for constipation?

Answer 6

· Dietary Fiber: 20–25 g/day via fruits, vegetables, whole grains, bran.
· Fluid Intake: ≥1.5–2 L/day (unless contraindicated).
· Physical Activity: Regular exercise to stimulate motility.
· Bowel Training: Respond to urges, establish regular routine.
· Biofeedback: For pelvic floor dysfunction (success rate 65–80%).
· Avoid constipating medications if possible.

Question 7

What should be monitored in patients being treated for constipation?

Answer 7

· Bowel movement frequency & consistency (Bristol Stool Scale).
· Symptoms: Straining, pain, bloating, completeness of evacuation.
· Medication adherence & laxative overuse/misuse.
· Adverse effects:
· Bulk agents → bloating, flatulence, obstruction if inadequate fluids.
· Osmotics → electrolytes (Mg²⁺, Na⁺), diarrhea.
· Stimulants → cramping, dependency, melanosis coli.
· Secretagogues → nausea (lubiprostone), diarrhea (linaclotide).
· Underlying condition control (e.g., thyroid function, glycemic control).

Question 8

How is constipation diagnosed?

Answer 8

Diagnosis:
· Rome III Criteria (≥2 for ≥25% of stools):
1. Straining
2. Lumpy/hard stools
3. Sensation of incomplete evacuation
4. Sensation of anorectal obstruction
5. Manual maneuvers to facilitate
6. <3 bowel movements/week.
· History: Onset, duration, diet, meds, laxative use, red flags (weight loss, bleeding, anemia, family history of CRC).
· Physical: Abdominal exam, digital rectal exam (tone, impaction).
· Tests: Thyroid function, electrolytes, colonoscopy if red flags.

Question 9

what are the key clinical features of constipation?

Answer 9

Clinical Presentation:
· Infrequent stools (<3/week), hard/lumpy stool, straining, bloating, abdominal discomfort, incomplete evacuation, may require manual disimpaction.

Question 10

What is the stepwise pharmacological approach to treating constipation?

Answer 10

General Approach: Start with lifestyle changes, then escalate as needed.

1. First-Line:
   · Bulk-forming agents: Psyllium, methylcellulose, polycarbophil.
   · Osmotic laxatives: PEG 3350 (17 g/day) – preferred first-line (Grade A evidence).
2. Second-Line (if inadequate response):
   · Other Osmotics: Lactulose or sorbitol 15–30 mL daily.
   · Stimulant laxatives (short-term): Bisacodyl 5–15 mg orally or senna.
3. Third-Line/Alternatives (chronic/severe cases):
   · Secretagogues: Lubiprostone (24 mcg BID) or Linaclotide (145 mcg daily) for chronic idiopathic constipation/IBS-C.
   · Opioid-induced constipation (OIC): Methylnaltrexone SC, naloxegol oral, alvimopan (post-op).
   · Peripheral μ-antagonists: For OIC without reversing central analgesia.
4. Rescue/Intermittent Use:
   · Suppositories/enemas: Glycerin or bisacodyl suppositories.
   · Saline laxatives: Magnesium citrate – avoid in renal/CHE.