Treatment of chronic anal fissure by application of L-arginine gel: A phase II study in 15 patients

PURPOSE: Local application of exogenous nitric oxide donors, such as isosorbide dinitrate and glyceryl trinitrate, promotes fissure healing by reducing anal resting pressure and improving anodermal blood flow. The major drawback of these nitric oxide donors is headache. The overall incidence of this side effect is approximately 40 percent. Recently we have shown in healthy volunteers that L-arginine, being an intrinsic precursor of nitric oxide, reduces anal resting pressure without headache as a side effect. The aim of the present study was to evaluate the effect of L-arginine on anal resting pressure, anodermal blood flow, and fissure healing in patients with chronic anal fissure. METHODS: Fifteen patients with a chronic anal fissure were included in the present study. Before entering the study 10 patients were unsuccessfully treated by local application of isosorbide dinitrate. Six of these patients experienced severe headache during treatment with isosorbide dinitrate. All patients were treated for at least 12 weeks by local application of a gel containing L-arginine 400 mg/ml five times a day. In patients with a persistent fissure, treatment was continued until 18 weeks. Anal manometry and laser Doppler flowmetry of the anoderm were performed before treatment, 20 minutes after local application of the first dose, and after 12 weeks of treatment. A visual analog scale was used to assess fissure-related pain and headache. RESULTS: One patient dropped out after one day of treatment, and one was excluded because of violation of the study protocol. After 12 weeks of treatment complete fissure healing was observed in 3 of 13 (23 percent) patients, and after 18 weeks the healing rate was 8 of 13 (62 percent) patients. None of the 13 patients experienced typical nitric oxide-induced headache. The pressure recordings showed a significant reduction of maximum anal resting pressure (mean +/- SD): pretreatment 89 +/- 17 mmHg; 20 minutes after application of the first dose 67 17 mmHg; 12 weeks after treatment 74 +/- 14 mmHg (P < 0.005). Recordings of anodermal blood flow showed a significant increase in flow: pretreatment 0.36 +/- 0.25 volts; 20 minutes after application of the first dose 0.59 +/- 0.27; 12 weeks after treatment 0.64 +/- 0.33 (P < 0.005). CONCLUSIONS: Local application of L-arginine promotes fissure healing without headache as a side effect, and L-arginine is effective even in patients not responding to isosorbide dinitrate treatment.