Glyceryl trinitrate ointment (GTO): Commercially available aluminium tubes containing 0.4 glyceryl trinitrate ointment (Rectogesic, proStrakan Group, Galashiels, UK) were purchased from pharmacies. The dosage for all the patients was 375 mg of ointment (containing 1.5 mg of glyceryl trinitrate), applied with a gloved finger to the distal anal canal, every 12 hours for an 8-week period.