About the condition
Anal fissure is a cut or tear in the anal canal. It is associated with severe anal pain and bleeding on defecation, causing substantial morbidity in otherwise healthy individuals. It has an estimated lifetime risk of 7.8%.
Chronicity is associated with a spasm of the internal anal sphincter muscle which increases the resting pressure in the anal canal which in turn reduces anodermal blood flow.
Anatomical, angiographic, and blood flow studies have demonstrated that the blood supply of the anal epithelium is very poor in the posterior midline which is where the majority of anal fissures occur.
Sustained elevated resting anal pressure also causes a reduction in the number of transient relaxations of the internal anal sphincter.
Idiopathic anal fissures are believed to result from trauma as a consequence of passing a large or hard stool. Whilst physical trauma may be the initiating event, a key characteristic is an increase in anal sphincter pressure (excessive tone).
Coupled with a compromised local blood flow, this results in painful defaecation and delayed healing.
Diltiazem is a potent smooth muscle relaxant and vasodilator. Thus, it has the potential to relax the smooth muscle of the internal anal sphincter and, in principle, treat the symptoms of anal fissure.
Treatment
The key target for treatment is relief of pain and facilitation of healing through reduction of anal sphincter pressure.2
The surgical procedure, lateral sphincterotomy, involves division of the internal anal sphincter (IAS). This improves symptoms and promotes healing, but risks causing faecal incontinence (in up to 45% of cases).3
Pharmacological treatments have the advantage of avoiding damage to the IAS. Glyceryl trinitrate (GTN) ointment [Rectogesic / Rectiv], applied locally, relaxes the IAS. It has licensing authorisation for the relief of pain associated with chronic anal fissure. However, it causes headache in up to 57% of patients,4 which can result in poor compliance and treatment failure.
Intra-sphincteric injections of botulinum toxin have been used also. However, this is an invasive and expensive procedure.
Topically applied diltiazem hydrochloride cream also relaxes the IAS. The benefits of diltiazem hydrochloride cream in the treatment of anal fissure (prescribed on a named patient basis), are recognised in a position statement by the influential Association of Coloproctology of Great Britain & Ireland (ACPGBI).2
