What is the dose and concentration of nitroglycerin (glyceryl trinitrate) paste for treating anal fissures?

Nitroglycerin Paste for Anal Fissures: Dosage and Concentration

The recommended concentration for nitroglycerin paste in treating anal fissures is 0.4%, applied twice daily with a dose of 375 mg of ointment (delivering 1.5 mg of nitroglycerin per application or 3 mg daily). 1

Treatment Algorithm for Anal Fissures

First-Line Treatment: Conservative Management

• Non-operative management is strongly recommended as first-line treatment for acute anal fissures 2
• Core components:
  • Dietary modifications: increased fiber and water intake
  • Sitz baths
  • Topical analgesics (lidocaine) for pain control

Second-Line Treatment: Chemical Sphincterotomy

When conservative measures fail, chemical sphincterotomy with nitroglycerin paste is indicated:

1. Dosing specifications:

   • Concentration: 0.4% nitroglycerin ointment 1
   • Amount per application: 375 mg of ointment
   • Application frequency: Twice daily
   • Total daily dose: 3 mg of nitroglycerin
   • Duration: Minimum 6 weeks, with pain relief typically occurring after 14 days 2

2. Application method:

   • Intra-anal application is superior to perianal application
   • Controlled intra-anal dosing produces greater reduction in sphincteric pressure and fewer headaches 3

Mechanism of Action and Efficacy

Nitroglycerin (glyceryl trinitrate) works as a nitric oxide donor that:

• Reduces the increased anal canal pressure caused by hypertonic internal anal sphincter
• Improves anodermal blood flow
• Promotes healing of the fissure 1

Efficacy rates vary:

• Early studies showed 70-80% healing rates
• More recent studies show lower healing rates (25-50%) 2
• Complete healing may occur within 2-4 weeks in many patients 4, 5

Side Effects and Monitoring

The most common side effect is headache:

• Occurs in most recipients 1
• Severe in 20-25% of patients
• Transient in nature
• Can be minimized with proper intra-anal application technique 3

Other potential side effects:

• Local burning sensation 5
• Hypotension (less common than with perianal application) 2

Important Considerations and Caveats

1. Patient selection:

   • Best for acute anal fissures or early chronic fissures
   • Surgical options (lateral internal sphincterotomy) should be considered for:
     • Patients with severe disabling pain requiring rapid relief
     • Fissures not responding to 4-8 weeks of nitroglycerin therapy 5, 2

2. Application technique matters:

   • Controlled intra-anal dosing is superior to perianal application
   • Proper application reduces headache incidence (10% vs 83%) 3

3. Alternative medical treatments:

   • Calcium channel blockers (diltiazem or nifedipine) may be more effective than nitroglycerin with fewer side effects 2
   • Consider these alternatives if nitroglycerin causes intolerable headaches

4. Treatment duration:

   • Minimum 6 weeks of therapy is suggested
   • Pain relief typically occurs after 14 days
   • Complete healing may take 4-8 weeks 2

Nitroglycerin paste remains an important non-surgical option for anal fissures, offering a balance between efficacy and avoiding the potential continence disturbances associated with surgical sphincterotomy.