Anal fissure is an ischaemic ulcer of the anal mucosa, caused by hypertonicity of the internal anal sphincter (IAS). The most common site is the posterior midline of the anal canal. Nitric oxide has been shown as an important inhibitory neurotransmitter in the IAS. Organic nitrates are degraded by cellular metabolism, releasing nitric oxide. Glyceryl trinitrate ointment releases nitric oxide, and if applied to the anal mucosa causes a fall in maximum anal resting pressure due to relaxation of the internal anal sphincter muscle, amounting to a reversible 'chemical sphincterotomy'.
Exclusive offer for doctors
Register for a MIMS account and receive free medical publications worth $139 a year.
Sign Out
