Topical Muscle Relaxant and Local Anesthetic for Painful Defecation in Constipation
For a 17-year-old with constipation and painful defecation, apply topical 0.3% nifedipine combined with 1.5% lidocaine ointment every 12 hours for two weeks, which achieves 92% resolution of pain compared to 45.8% with lidocaine alone. 1
Recommended Topical Treatment
The combination ointment works by relaxing internal anal sphincter hypertonicity (nifedipine) while providing immediate pain relief (lidocaine), addressing both the underlying muscle spasm and the symptom of pain. 1
- Apply the 0.3% nifedipine/1.5% lidocaine ointment directly to the anal area every 12 hours for a full two-week course 1
- No systemic side effects have been observed with topical nifedipine application, making it safe for a 17-year-old patient 1
- This formulation is superior to topical nitrates (like nitroglycerin), which show good results but cause headaches in up to 50% of patients 1
Alternative Local Anesthetic Options
If the combination ointment is unavailable, you can use:
- Lidocaine 1.5-2% ointment or cream alone for symptomatic pain relief, though this addresses only the pain and not the underlying sphincter spasm 1, 2
- Lidocaine provides temporary relief of minor pain and can be applied as needed 2
- For severe pain, lidocaine 5% patches can be applied for up to 12-24 hours for gradual pain relief 3
Critical Concurrent Treatment for the Underlying Constipation
You must simultaneously address the constipation itself, as painful defecation creates a vicious cycle of spasm-pain-spasm that perpetuates both problems. 4
Immediate interventions:
- Start polyethylene glycol (PEG) 17g daily as the primary osmotic laxative to soften stool and reduce straining 1, 5
- Add bisacodyl 10-15mg, administered 30 minutes after a meal to synergize with the gastrocolic reflex 1, 5
- Increase water intake substantially to support the PEG's effectiveness 5
- Increase dietary fiber to 25-30 grams daily (can use psyllium husk 5-6 teaspoonfuls with 600mL water daily) 1
If fecal impaction is present:
- Perform digital rectal examination immediately to rule out impaction, as the sensation of incomplete evacuation suggests this complication 5
- Use glycerin suppositories as first-line treatment for impaction 5
- Manual disimpaction may be necessary if suppositories fail 5
What NOT to Use
- Avoid topical corticosteroids beyond 7 days maximum, as prolonged use causes thinning of perianal and anal mucosa, increasing injury risk 1, 3
- Do not use docusate (stool softeners) routinely, as they have not shown additional benefit when used with other laxatives 5, 6
- Avoid increasing fiber if fluid intake is inadequate, as this may worsen symptoms 5
When to Escalate Care
If symptoms persist after 4 weeks of optimal medical treatment (topical therapy + laxatives), the patient requires anorectal testing to evaluate for a defecatory disorder. 5
- Anorectal manometry can identify pelvic floor dyssynergia (paradoxical contraction during defecation) 5
- Biofeedback therapy is the treatment of choice for defecatory disorders, with improvement in over 70% of patients 1, 5, 7, 8
- Biofeedback teaches relaxation of pelvic floor muscles during straining and improves coordination 1, 5
Common Pitfall to Avoid
Never assume the pain is solely from hemorrhoids or anal fissure without proper examination—up to 20% of constipated patients have concurrent anal fissures, and the treatment approach differs. 3 The combination of constipation with painful defecation in a young patient most commonly represents anal fissure secondary to hard stool passage, which is why the nifedipine/lidocaine combination is so effective—it addresses the sphincter hypertonia that perpetuates fissure formation. 1