Symptoms of IBS-D can be so relentless and incapacitating that it is often hard to believe that diagnostic testing doesn’t reveal any inflammation or tissue damage. IBS-D is therefore classified as a functional gastrointestinal disorder, because the problem has to do with how the system functions, as opposed to any visible disease process.
There is no cure for IBS-D, but a variety of medications may be prescribed to reduce the symptoms of pain, cramping and diarrhea. Remember that since IBS is a chronic condition, and medications may have side effects, it is essential to explore non-drug strategies (including stress management and dietary modifications) in addition to taking medication. Here is an overview of some of the options that are available to your doctor in helping you to manage your IBS:
Gut-Directed 5-HT3 Medication
A relatively new approach to understanding and treating IBS involves looking at particular neurotransmitters found in the intestinal system. Neurotransmitters are chemicals that relay information among nerve cells. The gut appears to have its own “brain” and it is this information system that is receiving attention in IBS research.It is believed that neurotransmitters within this system are responsible for regulating the process of digestion, including muscle contractions, mucus secretion and fluid absorption. Medications that target these neurotransmitters would therefore help make the system healthier.
5-HT3 refers to specific receptor sites for certain neurotransmitters found within the gut. Medications in this class appear to prevent the serotonin from attaching to the 5-HT3 receptors. The end result is a slowing of intestinal contractions, thereby reducing diarrhea and urgency. Lotronex, Zofran, Kytril, and Remeron are all classified as 5-HT3 medications. Of these, only Lotronex is designed specifically for the treatment of IBS-D. Zofran and Kytril are used to reduce nausea and vomiting associated with cancer treatment and Remeron is an antidepressant.
- Lotronex (alosetron)
In response to a significant consumer outcry, Lotronex was again made available as of June 2002, but with severe restrictions in terms of prescription. Lotronex is only able to be prescribed to women with severe diarrhea-predominant IBS who have not responded well to any other treatment. Constipation remains a common side effect of Lotronex: Anyone taking Lotronex who experiences constipation should immediately contact their doctor.
Antispasmodics/Anticholinergics
This class of medications targets and reduces the neurotransmitter acetylcholine in the nervous system with the result of slowing and reducing contractions of the muscles in the intestinal system. Their benefit for diarrhea predominant IBS comes from the reduction in the secretion of mucus and intestinal spasms. This anticholinergic effect is the same as seen in the tricyclic antidepressants and thus may result in similar side effects.Antidepressants
Although commonly prescribed for the treatment of depression and anxiety, antidepressants are sometimes prescribed due to their beneficial effects on IBS symptoms. It is not yet known precisely why this positive effect occurs. It may be due to the medication having an effect on neurotransmitters found in both the brain and the gut, it may have something to do with an effect on the communication between the gut and brain in terms of the stress response, or it may have to do with the effect of these medications on the parts of the brain that are involved in stress and/or pain response.Tricyclic Antidepressants: Tricyclic antidepresants are the elder statesmen of the antidepressants. It has been well-documented that tricyclic antidepressants have anti-pain and gut-slowing qualities and seem to do so by acting on the neurotransmitters of serotonin, norepinephrine, and dopamine. Unfortunately, the same action (anticholinergic effect) that results in slowing down the intestinal tract also causes a variety of side effects including drowsiness, dry mouth, blurred vision, sexual problems, dizziness, tremors, headache and weight gain.
- Elavil (amitriptyline)
- Tofranil (imipramine)
- Norpramin (desipramin)
- Aventyl, Pamelor, Allegron, (nortriptyline)
Selective Seritonin Reuptake Inhibitors (SSRIs): Selective serotonin reuptake inhibitors (SSRIs) are medications that were designed to increase the level of the neurotransmitter serotonin in the nervous system with a beneficial effect on mood. Because only the neurotransmitter serotonin is targetted, SSRIs generally have fewer side effects than the tricyclic antidepressants. Common side effects of nausea, diarrhea, anxiety, and headache often lessen as the body adjusts to the medication. Sexual difficulties (loss of sex drive and/or difficulty achieving orgasm) and weight gain may be a prolonged effect. It is important to remember that different people react differently and a person may tolerate one type of SSRI better than another.
