Irritable bowel syndrome (IBS) is a common disorder which is very disabling affecting as many as 20% of people in the US and accounting for 20-50% of visits to gastroenterologists. IBS is characterized by symptoms including abdominal pain, altered bowel function, bloating, distension, and feelings of incomplete evacuation (as in you didn't get rid of everything when you sat on the toilet). Patients have been sub classified according to whether they have predominant symptoms of diarrhea or constipation.
Alosetron (Lotronex) and cilansetron (Calmactin) are 5HT-3 serotonin receptor antagonists; these drugs act by blocking these particular serotonin receptors in the gut and act by an incompletely understood mechanism to reduce pain and retard bowel transit in IBS patients. Although both medications were shown to be effective for IBS, alosetron is effective only in women with IBS.
The 5HT-3 serotonin receptor antagonists have been very controversial. Concerns about the potential toxicities of these drugs have been countered by the protests of IBS sufferers that they have no other available remedies. Alosetron was introduced in the US in 2000 and subsequently withdrawn because several patients developed ischaemic colitis and severe constipation, and three patients died. Cases of ischaemic colitis have also been reported with cilansetron. Other possible side effects include headache, diarrhea, and stomach pain.
Tegaserod (Zelnorm) is a 5-HT-4 serotonin receptor partial agonist that promotes contractions of the colon that is effective in women with constipation predominant IBS. Common side effects include diarrhea in 5% over placebo and headaches in 3% over placebo. It has also been linked more rarely with ischaemic colitis, with 20 cases reported to the FDA from 2002 to 2004.
Cromolyn sodium is a mast cell stabilizer that has been used in the treatment of IBS. Two controlled studies showed an improvement in IBS symptoms with cromolyn sodium compared to placebo treatment. Side effects include sore throat, bad taste in the mouth, stomach pain, cough, stuffy nose, sneezing, headache, and (more serious) increased difficulty breathing, and swelling of the tongue or throat.
These medication treatments may offer some relief for some people with IBS. Talk to your doctor and decide what is right for you.