From the Guidelines
Nitroglycerin ointment for anal fissures is typically prescribed as a 0.2% or 0.4% concentration, with the standard dosing being a pea-sized amount (approximately 1 cm or 375 mg of ointment) applied to the anal canal every 12 hours for 6-8 weeks. To apply, use a finger cot or glove and gently insert the ointment just inside the anal canal. Start with the lower concentration if available, as this may reduce side effects while maintaining efficacy. The most common side effect is headache, which occurs in up to 50% of patients and typically diminishes with continued use. Taking acetaminophen 30 minutes before application can help prevent headaches. Nitroglycerin works by relaxing the internal anal sphincter, increasing blood flow to the area, and reducing pain and spasm, which promotes healing of the fissure. Patients should be advised to avoid standing up quickly after application to minimize lightheadedness and to wash hands thoroughly after use. If symptoms persist after 8 weeks of treatment, reassessment is recommended, as suggested by the American Gastroenterological Association medical position statement 1. However, the most recent guidelines from 2021 suggest the integration of topical anesthetics and common pain killers for pain control in patients with acute anal fissure, but do not provide specific recommendations for nitroglycerin dosing 1. Given the lack of recent, high-quality evidence on nitroglycerin dosing, the previous recommendations remain the most widely accepted approach. Key points to consider when prescribing nitroglycerin ointment for anal fissures include:
- Starting with a lower concentration to minimize side effects
- Applying the ointment every 12 hours for 6-8 weeks
- Advising patients to avoid standing up quickly after application and to wash hands thoroughly after use
- Monitoring for headaches and other side effects, and adjusting the treatment plan as needed.
From the Research
Nitroglycerin Topical Dosing for Fissure
- The use of nitroglycerin ointment for the treatment of chronic anal fissure has been studied in several clinical trials 2, 3.
- A study published in The New England Journal of Medicine in 1999 compared the effectiveness of botulinum toxin injections and topical nitroglycerin ointment for the treatment of chronic anal fissure, and found that 60% of patients in the nitroglycerin group had healed fissures after two months, compared to 96% in the botulinum toxin group 2.
- Another study published in the Australian Journal of General Practice in 2024 reviewed the current treatment options for anal fissures, including topical nitrates, and noted that they can be used as a conservative treatment option for acute and chronic fissures 3.
- However, there is limited information available on the specific dosing of nitroglycerin ointment for fissure treatment, with one study using a 0.2 percent nitroglycerin ointment applied twice daily for six weeks 2.
Comparison with Other Treatments
- Nitroglycerin ointment has been compared to other treatment options, including botulinum toxin injections and lateral internal sphincterotomy, in several studies 2, 4, 5, 6.
- A study published in Updates in Surgery in 2013 compared the effectiveness of conservative treatment with nifedipine ointment and lateral internal sphincterotomy for chronic anal fissure, and found that 68.9% of patients in the nifedipine group had healed fissures after eight weeks, compared to 88.2% in the sphincterotomy group 4.
- Another study published in BMC Gastroenterology in 2004 compared the effectiveness of botulinum toxin injections and lateral internal sphincterotomy for chronic anal fissure, and found that both treatments were effective in reducing anal sphincter pressures and promoting fissure healing 5.
Adverse Effects
- The use of nitroglycerin ointment for fissure treatment has been associated with adverse effects, including headaches 2.
- A study published in The New England Journal of Medicine in 1999 found that five patients in the nitroglycerin group experienced transient, moderate-to-severe headaches during treatment 2.