Irish journal of medical science
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Nitric oxide (NO) has diverse roles as a biological messenger. [1] Topically applied nitrate donors cause relaxation of the internal anal sphincter (IAS) and facilitate healing of anal fissures [2,3]. Systemic nitrates are commonly used for the treatment of ischaemic heart disease, yet the effects of systemically administered nitrates on the smooth muscle of the IAS are unknown. ⋯ Systemic nitrates significantly inhibit internal anal sphincter function.