TOPICAL GLYCERYL TRINITRATE IN THE TREATMENT OF CHRONIC ANAL-FISSURE

The aetiology of anal fissure is unclear, but there is an association with high maximum resting pressure (MRP). Internal sphincterotomy redu ces MRP and heals fissure through an increase in local blood supply, G lyceryl trinitrate (GTN) is a nitric oxide donor which contributes to internal anal sphincter relaxation via a non-adrenergic non-cholinergi c pathway. GTN ointment was applied topically in different concentrati ons to the anal margin in patients with chronic anal fissure to monito r its effect primarily on MRP and secondarily on fissure healing. Nine teen patients with chronic anal fissure were treated with ointment con taining increasing concentrations of GTN (0.2-0.8 per cent) to produce a reduction in MRP of greater than 25 per cent. The actual dose of GT N varied as no standard delivery system has been developed, but a 'typ ical amount' of GTN ointment weighed about 200 mg. In 15 of 19 patient s, a concentration greater than 0.2 per cent was required to lower the MRP by at least 25 per cent. The minimum concentration of GTN that re duced the resting pressure by at least 25 per cent was prescribed and local application was carried out by the patient twice daily for 6 wee ks. At 6 weeks, nine patients had healed, six required sphincterotomy and four were lost to followup. Eight of the nine patients with healed fistula required a GTN concentration of 0.3 per cent or more. Sixteen patients were resistant to the usually effective dose of 0.2 per cent GTN. In three there was tachyphylaxis and the duration of action of G TN was less than the 12 h described previously in control patients. Tw o patients did not fulfil the study because of headache.