What treatment options are available for headaches associated with constipation and the need to have a bowel movement?

Treatment of Headaches Associated with Constipation

Treat the underlying constipation aggressively with a stepwise laxative regimen, as resolution of constipation consistently improves or eliminates these headaches, particularly in patients with tension-type headache patterns.

Evidence for the Connection

The relationship between constipation and headache is well-established, with studies demonstrating that 25% of children and adolescents presenting with primary headache also have constipation, and all showed improvement in both conditions when constipation was treated 1. This association is particularly strong in tension-type headaches 1, 2. A randomized controlled trial showed that treating constipation with lactulose as an adjunct to standard migraine therapy significantly reduced both disability scores and pain severity compared to migraine treatment alone 3.

Initial Assessment

Before initiating treatment, you must:

• Rule out fecal impaction through physical examination, especially if overflow diarrhea is present 4, 5, 6
• Assess for bowel obstruction clinically 4, 5
• Check for metabolic causes: hypercalcemia, hypokalemia, hypothyroidism, and diabetes mellitus 4, 5, 6
• Discontinue any non-essential constipating medications (anticholinergics, antacids, opioids if applicable) 4, 5

Stepwise Treatment Algorithm

Step 1: Lifestyle Modifications + First-Line Laxative

• Start a stimulant laxative immediately: senna or bisacodyl 10-15 mg, 2-3 times daily 4, 6
• Goal: one non-forced bowel movement every 1-2 days (not necessarily daily) 4, 6, 7
• Increase fluid intake and physical activity when appropriate 4, 5, 6
• Add dietary fiber ONLY if patient has adequate fluid intake (at least 2 liters daily) 6, 7

Critical Pitfall: Do NOT add stool softeners like docusate to senna—evidence shows no additional benefit 4, 6. Fiber supplements alone are ineffective for medication-induced constipation 6.

Step 2: Add Osmotic Laxative (if constipation persists after 3-7 days)

Choose one of the following:

• Polyethylene glycol (PEG) 17g once daily in 8 ounces of liquid (preferred first-line osmotic agent with strongest evidence) 4, 6, 7
• Lactulose (particularly relevant given the RCT showing headache improvement) 4, 6, 3
• Magnesium hydroxide or magnesium citrate 4, 6
• Rectal bisacodyl suppository once daily 4, 6

For acute relief if several days without bowel movement: Glycerin suppository works through local irritation and drawing water into the rectum 5.

Step 3: Add Prokinetic Agent (if gastroparesis suspected)

• Metoclopramide 10-20 mg, 2-3 times daily 4, 6
• This is particularly relevant if the patient has nausea, early satiety, or is on medications that slow gastric emptying 6

Critical Pitfall: Do NOT use metoclopramide if complete bowel obstruction is present—only use in partial obstruction 4.

Step 4: Consider Newer Secretagogues (for refractory cases)

If standard laxatives fail after appropriate trial:

• Linaclotide (guanylate cyclase-C agonist)—most efficacious for IBS with constipation, though diarrhea is common 4, 6
• Lubiprostone (chloride channel activator)—less likely to cause diarrhea but nausea is frequent 4, 6
• Plecanatide (another guanylate cyclase-C agonist) 4, 6

Monitoring and Follow-Up

• Reassess after 7 days if no improvement—this may indicate serious pathology requiring further evaluation 8
• Monitor for rectal bleeding or failure to have bowel movement, which may indicate serious conditions 8
• Track both constipation resolution AND headache improvement together 1, 3

Special Considerations

The mechanism linking constipation and headache likely involves: central sensitization, parasympathetic referred pain, serotonin pathways, autonomic nervous system dysfunction, or shared pathophysiology 9, 1. This explains why treating the constipation resolves the headache rather than requiring separate headache-specific therapy.

If incomplete evacuation sensation persists despite regular bowel movements: Consider defecatory disorders (present in 59% of constipated patients) and proceed to anorectal manometry and balloon expulsion testing 7. Pelvic floor biofeedback therapy improves symptoms in >70% of patients with dyssynergic defecation 7.