Irritable bowel syndrome (IBS) is a long-lasting, relapsing disorder characterized
by abdominal pain/discomfort and altered bowel habits. Intestinal motility impairment
and visceral hypersensitivity are the key factors among its multifactorial pathogenesis,
both of which require effective treatment. Voltage-gated calcium channels mediate
smooth muscle contraction and endocrine secretion and play important roles in neuronal
transmission. Antispasmodics are a group of drugs that have been used in the treatment
of IBS for decades. Alverine citrate, a spasmolytic, decreases the sensitivity of
smooth muscle contractile proteins to calcium, and it is a selective 5-HT1A receptor
antagonist. Alverine, in combination with simethicone, has been demonstrated to effectively
reduce abdominal pain and discomfort in a large placebo-controlled trial. Mebeverine
is a musculotropic agent that potently blocks intestinal peristalsis. Non-placebo-controlled
trials have shown positive effects of mebeverine in IBS regarding symptom control;
nevertheless, in recent placebo-controlled studies, mebeverine did not exhibit superiority
over placebo. Otilonium bromide is poorly absorbed from the GI tract, where it acts
locally as an L-type calcium channel blocker, an antimuscarinic and a tachykinin NK2
receptor antagonist. Otilonium has effectively reduced pain and improved defecation
alterations in placebo-controlled trials in IBS patients. Pinaverium bromide is also
an L-type calcium channel blocker that acts locally in the GI tract. Pinaverium improves
motility disorders and consequently reduces stool problems in IBS patients. Phloroglucinol
and trimethylphloroglucinol are non-specific antispasmodics that reduced pain in IBS
patients in a placebo-controlled trial. Antispasmodics have excellent safety profiles.
T-type calcium channel blockers can abolish visceral hypersensitivity in animal models,
which makes them potential candidates for the development of novel therapeutic agents
in the treatment of IBS.
