Can constipation cause headaches and how can they be treated?

Constipation and Headaches: The Connection and Treatment

Yes, constipation can cause headaches, and treating the constipation with polyethylene glycol (PEG) is the most effective first-line approach to relieve both conditions.

The Connection Between Constipation and Headaches

Research has demonstrated a significant relationship between constipation and headaches, particularly in certain types of headaches:

• Studies show that 25% of patients with primary headache also have constipation 1
• Resolution of constipation improves headache symptoms in many patients 2, 1, 3
• The association is particularly strong with tension-type headaches 1
• There is a 4.2 times higher prevalence of headache among constipated individuals compared to those without constipation 4

Mechanism of Constipation-Related Headaches

Several potential mechanisms may explain this connection:

• Shared pathophysiology between constipation and headache disorders
• Increased intra-abdominal pressure during straining may affect cerebral blood flow
• Common neurotransmitter disturbances (particularly serotonin)
• Emotional stress, depression, and anxiety affecting both conditions
• Toxin buildup from prolonged stool retention potentially affecting neural function

Treatment Algorithm for Constipation-Related Headaches

First-Line Treatment:

1. Polyethylene glycol (PEG) 17-34g daily with adequate water intake
   • Strong recommendation with moderate quality evidence 5, 6
   • Superior efficacy compared to other treatments 7
   • Common side effects: abdominal distension, loose stool, flatulence 6

If Inadequate Response After 1-2 Weeks:

1. Add a stimulant laxative:
   • Bisacodyl 10-15mg daily (strong recommendation) 5, 6
   • OR Senna 2-3 tablets twice daily (conditional recommendation) 5, 6
   • Goal: one non-forced bowel movement every 1-2 days 5

For Persistent Constipation:

1. Add an osmotic agent:
   • Lactulose 15-30ml twice daily 5, 6
   • OR Magnesium salts (avoid in renal insufficiency) 5, 6

For Refractory Cases:

1. Consider prescription medications:
   • Linaclotide (strong recommendation) - may cause headache as side effect 5
   • Plecanatide (strong recommendation) 5
   • Prucalopride (strong recommendation) - note that headache is a common side effect 5
   • For opioid-induced constipation: methylnaltrexone 0.15mg/kg subcutaneously every other day 5

Lifestyle Modifications (Concurrent with Medication)

• Increase fluid intake within patient limits 5
• Increase physical activity as tolerated 5
• Optimize toileting habits (attempt defecation twice daily, 30 minutes after meals) 6
• Avoid medications that may cause constipation when possible (antacids, anticholinergics, antidepressants, antispasmodics, phenothiazines, haloperidol) 5

Important Considerations and Pitfalls

• Avoid relying solely on stool softeners without stimulant laxatives 6
• Avoid bulk-forming laxatives like psyllium for medication-induced constipation 6
• Monitor for red flags requiring immediate attention: severe abdominal pain, no bowel movement for >3 days, vomiting, signs of bowel obstruction 6
• Be aware that some constipation treatments (particularly prucalopride) may themselves cause headache as a side effect 5
• Consider the possibility of medication overuse headache if the patient is taking frequent analgesics for headache pain

Evidence for Treatment Efficacy

A randomized clinical trial showed that treatment of constipation with lactulose significantly reduced both the severity of disability and pain in patients with migraine compared to standard migraine treatment alone 2. This suggests that addressing constipation should be part of the comprehensive management of patients presenting with headaches.

Another study demonstrated that PEG laxative was superior to tegaserod for treating chronic constipation, with PEG patients experiencing significantly greater improvement in constipation symptoms 7. Notably, tegaserod patients experienced a significantly higher incidence of headaches, further supporting the connection between gastrointestinal function and headache symptoms.