Diltiazem hydrochloride is a calcium channel blocker and potent vasodilator. It increases blood flow to smooth muscles and relaxes muscle tone.
Anal fissure is a common and painful problem that involves a tear or ulcer in the squamous epithelium of the anus, usually located in the posterior midline. Anal fissure typically causes perianal itching and bleeding, and pain during defecation and for 1–2 hours afterwards,. The most common cause of anal fissure is passing particularly hard stools, leading to trauma. Other causes include inflammatory bowel disease, childbirth and sexually transmitted infection. Although the aetiology of chronic anal fissure is uncertain, it is assumed that pain causes an increased sphincter pressure leading to ischaemia of the anal sphincter. This inhibits fissure healing, generating a vicious circle of pain, constipation and prolonging of the healing process.
A Cochrane review of non-surgical treatments for chronic anal fissure states that chronicity is defined as a history of pain lasting more than 4 weeks or with pain of less duration but similar episodes in the past. Duration of symptoms was not uniform in the RCTs in adults considered in this evidence summary. In the study of 2% topical diltiazem in children considered in this evidence summary, an inclusion criterion was a history of anal fissure lasting more than 15 days.
Reduction of the increased pressure on the anal sphincter is associated with relief of pain and fissure healing. Conservative treatments include softening stools through laxatives or a high-fibre diet, as well as using topical anaesthetics or analgesics. Surgical lateral sphincterotomy is regarded as the current gold standard treatment and is highly effective, resulting in fissure healing in more than 90% of patients,. However, a significant minority of patients who receive surgery experience incontinence, and some reports have suggested that up to 30% of patients have difficulty controlling flatus and 3–10% have episodes of leakage after surgery (although other reports suggest substantially lower rates). Consequently, non-surgical options have been sought.
In the UK, 0.4% topical glyceryl trinitrate is the only licensed non-surgical treatment for chronic anal fissure. A Cochrane review found that glyceryl trinitrate was statistically significantly, better than placebo in healing anal fissure (48.9% compared with 35.5% respectively, p<0.0009), but late recurrence of fissure was common, in the range of 50% of those initially cured. Headache is very commonly reported by people using topical glyceryl trinitrate 0.4% .Although this can be treated with analgesics such as paracetamol, headaches may be severe (frequency 1 in 5 people) and cause people to discontinue treatment. Dizziness is also commonly reported (frequency greater than 1 in 100, but less than 1 in 10).
Non-surgical treatments other than topical diltiazem include botulinum toxin injection. However, a Cochrane review found that healing of anal fissure was more likely with sphincterotomy than with botulinum toxin (89.3% compared with 59.0% respectively).
 Samim M, Twigt B, Stoker L et al. (2012) Topical diltiazem cream versus botulinum toxin a for the treatment of chronic anal fissure: a double-blind randomized clinical trial. Annals of Surgery 255: 18–22
 Cross KLR, Massey EJD, Fowler AL et al. (2008) The Management of Anal Fissure: ACPGBI Position Statement. Colorectal Disease 10 (Suppl. 3): 1–7
 Cevik M, Boleken ME, Koruk I et al. (2012) A prospective, randomized, double-blind study comparing the efficacy of diltiazem, glyceryl trinitrate, and lidocaine for the treatment of anal fissure in children. Pediatric Surgery International 28: 411–6
 ProStrakan (2012) Rectogesic 4 mg/g rectal ointment summary of product characteristics