Medication for irritable bowel syndrome
The symptoms associated with irritable bowel syndrome will determine which medications may be recommended. There is no one medicine that can treat all the symptoms or provide a cure.
There are several main types of medications for treating irritable bowel syndrome (IBS), based on the symptoms. However, medication to treat one symptom can make another symptom worse or have side effects, so there may be some trial and error to find the most appropriate medications, or the ones to manage the most distressing symptoms.
What types of medications are available for treating constipation?
Laxatives for treating constipation, which are mostly available over the counter at pharmacies, include bulking agents, purgatives, osmotic laxatives and stimulants:
- Bulking agents, such as bran, psyllium, ispaghula husk or sterculia gum methylcellulose, contain complex sugars or starches that the small intestine cannot digest. They work in the colon, where they retain water and nourish bacteria, making the stools softer and bulkier. You need to drink plenty of water and it may take several days before symptoms improve, and at first you may have increased bloating, wind and pain. Symptoms should improve as your bowel adapts to the bulking agent, which should be taken twice a day, in the morning and evening. It is recommended that you start with a low dose and then increase it gradually if necessary to avoid the side effects of bloating and wind.
- Lactulose is an osmotic laxative; this type of laxative cannot be absorbed by the small intestine, and like bulking agents, retains water in the bowel that softens stools to make them easier to pass. Also like bulking agents, you need to drink plenty of water, and you may experience increased bloating, wind and pain that will gradually improve. The National Institute for Health and Care Excellence (NICE) says people with constipation in IBS should be discouraged from using lactulose.
- Faecal softeners, such as liquid paraffin, sodium docusate or docusol may be recommended if stools are hard. These lubricate the stool so they are easier to pass.
- Stimulant laxatives, such as senna or bisocodyl, work on the nervous system to stimulate secretion through colonic peristalsis (the contraction and relaxation of the colon to pass stools). As these can cause cramping, they are usually reserved for use in IBS only when other medicines are not working for severe constipation.
- Prokinetic agents, such as lubiprostone, prucalopride and linaclotide, also stimulate peristalsis, by acting on serotonin receptors in the gut.
Suppositories or enemas are sometimes used if hard faecal matter becomes lodged in the rectum. These work like other types of laxatives, either softening the stool and/or stimulating bowel action.
What types of medications are available for treating diarrhoea?
Several types of medicines are available over the counter for treating diarrhoea: