Therapeutic strategies in management of irritable bowel syndrome
The burden of IBS
The estimated prevalence of IBS in Hong Kong is 6.6 percent. [Hong Kong Med J 2017;23:641-647] “It exists in a spectrum ranging from a very mild to a more severe disease course. Some patients experience a relapsing and remitting course, while others have a more stable chronic presentation. It can impact a patient’s daily life due to abdominal pain and irregular bowel habits,” said Tan.
These guidelines, released by the Hong Kong Advisory Council on Irritable Bowel Syndrome, also covered patient assessment, understanding the patient’s psychological distress, and dietary and alternative approaches to managing IBS. [Hong Kong Med J 2017;23:641-647]
Low-FODMAP diet and other diets for IBS management
FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) are a group of carbohydrates and sugar alcohols that are generally absorbed in most individuals but cause discomfort among patients with visceral hypersensitivity, which is the cornerstone of IBS pathophysiology. FODMAPs are ubiquitous in the diet and can be found in vegetables, fruits, legumes, beans and grains. The low-FODMAP diet recommends limiting the intake of FODMAPs to 3–4 g/day. [Gastroenterol Hepatol (N Y) 2013;9:450-452; J Gastroenterol Hepatol 2010;25:252-258]
“Normally, our body does not readily absorb FODMAPs. Once they reach the distant small bowel and colon, they act as fuel for gut bacteria. This results in fermentation of carbohydrates and sugar alcohols and subsequent generation of short-chain fatty acids and gas. These molecules draw water to the gut, causing stretch and distension of the colon and stimulation of mechanoreceptors, resulting in abdominal pain. Low dietary intake of FODMAPs can reduce the pain resulting from this fermentation process,” explained Tan. [Gastroenterol Hepatol (N Y) 2013;9:450-452; J Gastroenterol Hepatol 2010;25:252-258]
“Key elements for the successful implementation of the low-FODMAP diet include high motivation of the patient and support from dietitians or nutritionists,” she added.
More recent studies have also associated IBS with impaired histamine degradation. The resulting excess histamine leads to symptoms mimicking allergic reactions, including diarrhoea, gastrointestinal upset as well as extraintestinal manifestations. [Neurogastroenterol Motil 2018, doi: 10.1111/nmo.13238]
Other diets which may be helpful for IBS include lactose-free diet and Chinese food therapy. “In a study by our group using breath test among 353 patients with IBS or functional dyspepsia [FD; mean age, 53 years (range, 18-76); 31 percent male], approximately 85 percent [95 percent confidence interval, 82 percent to 89 percent] of IBS or FD patients were found to be either lactose intolerant or lactose malabsorbers,” said Tan. [United European Gastroenterol J 2017, doi: 10.1177/2050640617725676]
“Chinese food therapy follows the concept of eating heating or cooling foods based on the patients’ symptoms. There is currently no scientific evidence for this diet, but there is anecdotal evidence for the use of this tradition of healing in managing gut disorders that appear to be similar to FD and IBS. We are actively researching in this area to investigate whether Chinese food therapy may be of benefit for IBS management,” Tan added. [J Clin Gastroenterol 2018;52:105-113]
Pharmacotherapy in IBS
Otilonium bromide is an antispasmodic with several modes of action, including blockade of L-type calcium channels on smooth muscle cells, antisecretory effect, and reduction of smooth muscle spasm through its antimuscarinic effects. In addition, its interaction with the NK1/NK2 tachykinergic receptors in sensory afferent nerves may also improve the visceral hypersensitivity that affects patients with IBS. [Ther Adv Gastroenterol 2017;10:311-322]
“Hyoscine n-butylbromide is an antispasmodic with high affinity for muscarinic receptors located on smooth muscle cells of the gastrointestinal tract. It is available in oral and intravenous formulations and is usually given to patients with severe colic in the accident and emergency or the inpatient setting. It is associated with various adverse effects [AEs], mainly anticholinergic effects such as cardiac arrhythmias, blurred vision, dry mouth and constipation,” commented Tan. [Drugs 2007;67:1343-1357]
“The major advantage of otilonium bromide over mebeverine, another musculotropic agent with antispasmodic activity and regulatory effects on bowel function, is that the number of studies on otilonium bromide far exceeds those on mebeverine. Otilonium bromide has also demonstrated a better safety profile compared with mebeverine,” she added. [World J Gastroenterol 2010;16:547-553]
In a systematic review and meta-analysis of randomized controlled trials, which compared fibre, antispasmodics and peppermint oil with placebo or no treatment in adults with IBS, otilonium bromide demonstrated a reduction in global symptoms of IBS with a safety profile similar to that of placebo. [BMJ 2008;337:a2313]
In a pooled analysis of three double-blind, placebo-controlled trials with a total of 883 IBS patients (69.8 percent women; mean age, 46.2 years), 442 patients were treated with otilonium bromide 40 mg daily for 15 weeks and 441 were treated with placebo. Results showed a greater reduction in global evaluation of pain index and bloating score among patients treated with otilonium bromide vs placebo. (Figures 1 and 2) [Therap Adv Gastroenterol 2017;10:311-322]
“Otilonium bromide is a very efficacious drug, as demonstrated in various studies. In my practice, I have not encountered any burdensome anticholinergic AEs associated with its use. However, it may not be the right choice for patients with severe abdominal colic in the acute setting. During these instances, a drug available in intravenous formulation may be a more preferable option,” opined Tan.
“I prescribe otilonium bromide on a long-term basis and give patients a 3-month treatment course initially. In the first-line setting, patients respond well to otilonium bromide therapy in terms of severity of abdominal pain and change in stool form,” she added.
IBS is a common condition with primary care physicians considered as the first port-of-call in its management. If initial therapy and simple investigations fail, referral to a gastroenterologist for further investigation and management should be done.
Options available for IBS management include natural and dietary therapy as well as pharmacotherapy. Dietary modifications, such as the low-FODMAP and lactose-free diets, have been shown useful in the management of IBS. Pharmacotherapy include medications that regulate gut motility, modulate visceral hypersensitivity or alter the gut microbiota.
“We are living in a time where the landscape for treating IBS is good because of the availability of numerous treatment options, a majority of which are supported by scientific research and evidence,” Tan commented.