Application of ISDN Cream for Anal Fissures
Apply isosorbide dinitrate (ISDN) cream at a dose of 2.5 mg digitally to the anal canal three times daily for at least 4-8 weeks, which achieves healing in approximately 83-93% of chronic anal fissures. 1, 2
Application Technique and Dosing
- Use digital application of 2.5 mg ISDN three times daily, as this dose provides superior reduction in maximum anal resting pressure compared to lower doses of 1.25 mg 1
- Apply the cream directly to the anal canal using a finger, ensuring contact with the internal anal sphincter 1, 3
- Continue application every 3 hours during waking hours (excluding nighttime), though three times daily dosing is the standard regimen 1, 3
Treatment Duration and Expected Outcomes
- Expect symptom relief within 6-7 days on average, though complete fissure healing requires longer treatment 1
- Continue treatment for a minimum of 4 weeks, with most fissures healing within 3 weeks of starting therapy 1
- If the fissure has not healed after 4 weeks, extend treatment up to 8-12 weeks before considering surgical options 2, 3
- Primary healing rates range from 83-93%, with complete healing achieved in most patients by 12 weeks 1, 2, 3
Essential Adjunctive Measures
- Prescribe fiber supplementation of 25-30g daily to soften stools and minimize anal trauma during defecation 4, 5
- Ensure adequate fluid intake to prevent constipation 4, 5
- Recommend warm sitz baths to promote sphincter relaxation 4, 5
- Consider adding topical lidocaine 5% for additional pain control during the initial treatment phase 5
Common Side Effects and Management
- Headache occurs in approximately 7-27% of patients and is typically mild and transient, resolving shortly after treatment initiation 2, 3
- All patients may experience some degree of headache, but this should not necessitate treatment discontinuation in most cases 3
- The headache side effect, combined with frequent application requirements, can lead to reduced compliance 6
Recurrence Management
- If recurrence occurs after initial healing (approximately 13-15% of cases), repeat the same ISDN regimen, which successfully treats 54% of recurrent fissures 2
- For patients who fail to respond after 4-8 weeks of treatment or experience multiple recurrences, refer for lateral internal sphincterotomy 1, 2
Critical Clinical Considerations
- ISDN works by donating nitric oxide, which mediates vasodilation and internal anal sphincter relaxation, increasing anodermal blood flow to the ischemic ulcer 1, 7
- This mechanism addresses the underlying pathophysiology of internal anal sphincter hypertonia and decreased perfusion 1, 7
- ISDN represents an effective alternative to surgical sphincterotomy, avoiding the 8-30% risk of permanent incontinence associated with surgical intervention 2, 7
Alternative Consideration
- Diltiazem 2% ointment applied twice daily may be preferred over ISDN due to similar efficacy (48-75% healing rates), lower application frequency, absence of systemic side effects like headache, and lower overall treatment costs 5, 6
- Compounded 0.3% nifedipine with 1.5% lidocaine applied three times daily achieves even higher healing rates of 95% after 6 weeks 4, 5
When to Abandon Medical Therapy
- Refer for lateral internal sphincterotomy after documented failure of 6-8 weeks of conservative medical management, as surgery remains the gold standard with >95% healing rates for chronic fissures 5
- Ensure atypical fissure locations (lateral or multiple fissures) are evaluated for underlying conditions like IBD, cancer, or infection before proceeding with standard treatment 5