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Appendix
Biology of IBS: The Role of Serotonin
Irritable bowel syndrome (IBS) is a multifactorial condition. Biologic, psychologic, and
environmental factors can act simultaneously to cause gastrointestinal (GI) dysfunction
(Fig. 19).16 Three major physiologic abnormalities contribute to IBS symptoms:
– altered motility (altered movement of food and waste through the digestive system)
– visceral hypersensitivity (an increased perception of pain in the abdominal area)
– altered intestinal secretion (altered movement of fluid in the digestive tract)
Serotonin, commonly referred to as hydroxytryptamine (5-HT), is a naturally occurring
chemical in the body that helps the digestive system function normally.7 The physiologic
abnormalities in IBS may be related to an imbalance of serotonin in the gut, an improper
reaction of the digestive system to serotonin, or a faulty communication network between
serotonin in the gut and the brain and spinal cord (known as brain-gut axis dysfunction).6,7
Serotonin plays a major role in
– modulating intestinal movement
– modulating perception of pain
– mediating secretion in the GI tract (release of water, which ultimately helps to
soften stools)
A greater understanding of brain-gut axis dysfunction and the role of serotonin in the physiology
of IBS has helped to establish IBS as real disease of the digestive tract and has led to a new
focus on medications directed at the underlying causes and multiple symptoms of IBS.8
Methodologies for the Patient and Physician Surveys
Novartis Pharmaceuticals Corporation engaged Lieberman Research Inc to conduct surveys
from June through August 2000 and in January 2002.
• GI Sufferer Study: This was a 1-hour, in-depth telephone survey with 1,013 GI sufferers
aged 18 and older screened from a nationally projectable random-digit dial sample who
had not been diagnosed with an organic GI disease and had a specified GI disorder. The
sample of 1,013 patients included both diagnosed (self-reported physician diagnosis) and
undiagnosed sufferers identified via responses to the Rome II criteria for IBS (n=411),
chronic constipation (n=207), functional dyspepsia (n=190), or bloating (n=205).
The IBS sample included 122 sufferers with constipation as the predominant bowel
symptom, 125 with diarrhea as the predominant symptom, and 164 who had alternating
constipation and diarrhea.
• Physician Study: A 55-minute telephone market survey focusing on IBS (all subtypes)
and chronic constipation symptoms, causes, treatments, and effectiveness of treatments. The
sample of 711 physicians included 509 primary care physicians, 181 gastroenterologists,
and a small sample of obstetricians/gynecologists and pediatricians.
The objectives of these 2 surveys were to understand IBS symptoms and treatment options;
to provide basic category information about the GI market; to identify attitudes, behaviors,
and unmet needs of consumers and physicians with regard to functional GI disorders; to
identify the common themes and gaps between physicians and consumers; to develop a
meaningful model for segmenting physicians and consumers; and to provide input for the
development of improved patient and physician education and communications.
• IBS Medications Side Effects Study: From a self-selected group of IBS sufferers who
responded to an online survey, patients were asked to participate in the Side Effects Study.
An online panel was used to select patients diagnosed with IBS. Sufferers were asked
whether they experience constipation predominantly (IBS with constipation), diarrhea
predominantly (IBS with diarrhea), or both with equal frequency (alternating IBS).
Sufferers of IBS with constipation were the primary targets of this study; those with
alternating IBS were a secondary target. Therefore, the self-reported sufferers of IBS
with diarrhea were not included in the study.
A total of 668 patients meeting survey criteria (504 with a diagnosis of IBS with constipation
and 164 with alternating IBS) completed a 20-minute survey focusing on treatments used
for IBS, satisfaction and efficacy of treatments, and side effects experienced. Of the sufferers with
IBS with constipation, 60% reported having taken medications and 59% had severe symptoms.
Of the IBS alternators, 65% had taken medications and 67% reported severe symptoms.
Methodology for the Omnibus Survey
Novartis Pharmaceuticals Corporation engaged TeleNation (a national survey company)
to conduct a telephone survey in May 2002.
A single-stage, random-digit dial sample technique was used to select 1,000 residential
telephone numbers in the contiguous United States. One thousand adults (480 men and
520 women) were interviewed by telephone regarding their perceptions of IBS and other
chronic conditions.
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