Studies on the mechanism of action of dioctyl sodium sulphosuccinate in the human jejunum

Treating constipation during pregnancy

QUESTION

Many of my patients experience constipation during pregnancy, even after increasing dietary fibre and fluids. Are there any safe treatments I can recommend to them?

ANSWER

Although the recommended first-line therapy for constipation includes increasing fibre, fluids, and exercise, these are sometimes ineffective. Therefore, laxatives such as bulk-forming agents, lubricant laxatives, stool softeners, osmotic laxatives, and stimulant laxatives might be considered. Although few of the various types of laxatives have been assessed for safety in pregnancy, they have minimal systemic absorption. Therefore, they are not expected to be associated with an increased risk of congenital anomalies. However, it is recommended that osmotic and stimulant laxatives be used only in the short term or occasionally to avoid dehydration or electrolyte imbalances in pregnant women.

Palliative care and pain: new strategies for managing opioid bowel dysfunction

Opioid analgesics are a cornerstone of pain therapy in the hospice and palliative care population. However, opioid-induced bowel dysfunction (OBD) is a commonly associated condition that frequently compromises the usefulness of these agents. Although its most common and debilitating symptom is constipation, the impact of OBD extends beyond constipation to encompass a myriad of gastrointestinal (GI) signs and symptoms, ranging from decreased gastric emptying and reflux to abdominal pain, cramping, bloating, nausea, and vomiting. Even after aggressive therapies to improve bowel function have been implemented, many patients continue to experience symptoms of OBD. To avoid these unwanted effects, some even choose to decrease or discontinue therapy with opioid analgesics, and experience inadequate pain control. The net result of OBD is a seriously negative impact on quality of life (QOL). For these reasons, it is important that palliative care practitioners have an adequate understanding of normal GI function and the underlying mechanisms responsible for OBD, the burden of OBD in the context of appropriate and effective pain management, and the benefits provided by effective pharmacotherapy. Several real-world cases are discussed to illustrate the application of optimal symptom management and the use of strategies that minimize the effects of OBD and improve patient QOL.

Cancer-related constipation

Cancer-related constipation is common and a significant detractor from patient quality of life. It has many possible causes and is still not well understood. Information is lacking on therapies for cancer-related constipation among current medications approved by the US Food and Drug Administration (FDA). Most agents have only been formally tested in comparison with placebo in chronic idiopathic constipation if at all. Few comparative studies of laxatives have been performed to establish superiority or synergy. As we understand more about the physiology of the gastrointestinal tract, new targeted therapies have become available. These include a selective chloride channel activator, lubiprostone, and a selective 5HT4 serotonin receptor agonist, tegaserod, both of which have been FDA approved for chronic idiopathic constipation. The role of these agents in cancer-related constipation remains to be seen. On the horizon are two investigational peripherally acting opioid receptor antagonists, alvimopan and methylnaltrexone. Preliminary results in cancer-related constipation suggest that these agents may be important additions to our treatment repertoire.

Review article: the therapy of constipation

Constipation is a common symptom that may be idiopathic or due to various identifiable disease processes. Laxatives are agents that add bulk to intestinal contents, that retain water within the bowel lumen by virtue of osmotic effects, or that stimulate intestinal secretion or motility, thereby increasing the frequency and ease of defecation. Drugs which improve constipation by stimulating gastrointestinal motility by direct actions on the enteric nervous system are under development. Other modalities used to treat constipation include biofeedback and surgery. Laxatives and lavage solutions are also used for colon preparation and evacuation of the bowels after toxic ingestions.

Gastrointestinal pharmacology

Diseases of the gastrointestinal tract that require pharmacologic management, usually in combination with other treatments, are gastric ulcers (omeprazole and others), colic (laxatives, analgesics), diarrhea (antibiotics, protectants and absorbents, glucocorticoids, motility inhibitors), reperfusion injury, postoperative ileus (prokinetic drugs), and adhesions. There is growing evidence that nonsteroidal anti-inflammatory drugs can alter important physiologic properties of the intestine; however, these drugs are valuable analgesics for horses and their use should be tempered with an awareness of their harmful effects. The role of antibiotics in treating gastrointestinal disease is controversial, but their ability to induce life-threatening diarrhea is well known and invites caution and defensible use of these drugs in horses.

Clinical pharmacology and use of laxatives and lavage solutions

Laxatives and lavage solutions are used in the treatment of constipation and toxic ingestion and also for preparation of the colon before endoscopic or surgical procedures. Several different categories of agents are available for use. These include bulking agents, osmotic agents, secretagogues and agents with direct effects on epithelial nerve or smooth muscle cells, and lubricating agents. Each category has different pharmacologic effects, side effects, and clinical indications. This review summarizes current information about these agents.

Gastrointestinal drugs

Various drugs are commonly used for the many gastrointestinal problems that are routinely seen in dogs and cats. Many of these drugs are briefly reviewed in this article. Anecdotal as well as documented findings are provided that will hopefully allow the clinician to use them wisely and effectively in the many clinical situations that arise daily. Emetics, although not used for gastrointestinal problems, are also reviewed because of their obvious connection with the gastrointestinal tract.

Neurogenic bowel dysfunction after spinal cord injury: clinical evaluation and rehabilitative management

Neurogenic bowel dysfunction (NBD) is one of many impairments that result from spinal cord injury (SCI). The experience of persons with SCI reveals that the risk and occurrence of fecal incontinence and difficulty with evacuation are particularly significant life-limiting problems. This review relates the anatomy and physiology of colon function to the specific pathophysiology that detracts from the quality of life of persons after SCI. There are two patterns of NBD after SCI: the upper motor neuron bowel, which results from a spinal cord lesion above the sacral level, and the lower motor neuron bowel, which results from a lesion to the sacral spinal cord, roots, or peripheral nerve innervation of the colon. Rehabilitation evaluation consists of a comprehensive history and examination to define impairments, disabilities, and handicaps pertinent to NBD. Rehabilitation goals include continence of stool, simple willful independent defecation, and prevention of gastrointestinal complications. Intervention consists of derivation and implementation of an individualized person-centered bowel program, which may include diet, oral/rectal medications, equipment, and scheduling of bowel care. Bowel care is a procedure devised to initiate defecation and accomplish fecal evacuation. Digital-rectal stimulation is a technique utilized during bowel care to open the anal sphincter and facilitate reflex peristalsis. Recent advances in rehabilitation practices, equipment, pharmacology, and surgery have offered patients new bowel program alternatives. Interdisciplinary development of solutions for problems of NBD are evolving rapidly.

Constipation in the elderly

OBJECTIVE

To explore the distinction between true clinical constipation and the subjective complaint of constipation in elderly people and to review the pathophysiology, symptoms, diagnosis, causes, and treatment.

DATA SOURCES

A computer-assisted and manual search of the English language literature using MEDLINE 1966-1991, Index Medicus 1988-1992, reference lists of selected articles, and relevant textbooks.

STUDY SELECTION

Studies that provide information on lower bowel function and laxative and enema use in the elderly subjects were reviewed. Article selection was not limited by study design.

DATA EXTRACTION

Relevant data were abstracted from the results of physiological, cohort and case-control studies, and clinical trials. The text discusses the methodological strengths and flaws of these studies and excludes management approaches formulated from uncontrolled clinical observation.

RESULTS OF DATA SYNTHESIS

Constipation of the elderly is not well defined in the current literature. Self-reported constipation and laxative use increase with age, while a similar escalation in true clinical constipation is not shown. Physiological changes in the lower bowel predisposing toward constipation do not occur with normal aging. Patient selection criteria for studies examining the pathophysiology of constipation differ in their definition of constipation and their inclusion of coexisting chronic illness. Nevertheless, there is consistent evidence for prolonged transit through the sigmoid colon and rectum, especially in frail elderly patients, and reduced rectal tone with impaired sensation, particularly in patients with rectal impaction. Few studies rigorously examine "risk factors" and non-pharmacological interventions in constipation. The results of most laxative trials require cautious interpretation because of inclusion of patients without diagnostically proven constipation, use of combined laxative preparations, and unreliable outcome measures. Certain laxative agents however appear more appropriate for use in elderly people.

CONCLUSION

Although the subjective complaint of constipation and habitual laxative use increase with age, the epidemiological data suggest that true clinical constipation does not. Physiological changes predisposing toward constipation are not an inevitable consequence of aging, but appear to be specific to the condition. The available data do not confirm many suspected "risk factors" nor the benefits of commonly used non-pharmacological and pharmacological treatments, but they do provide enough information to formulate a practical approach to constipation in elderly persons.

A new model of human secretory diarrhoea using cholera toxin

Secretory diarrhoea is a major cause of morbidity and mortality worldwide. However, there is no biologically relevant test system in man for assessing new anti-diarrhoeal therapies prior to clinical trial. We have used highly purified cholera toxin in combination with the triple lumen jejunal perfusion technique to establish a subclinical model of cholera in man. Cholera toxin was administered either by mouth with sodium bicarbonate or directly into a 30 cm 'open' or 'closed' (isolated between two inflated balloons) jejunal segment in healthy adult volunteers. Both oral dosing and direct delivery into an 'open' jejunal segment failed to produce consistent secretion of water and electrolytes. In contrast 15 micrograms or 25 micrograms of cholera toxin elicited secretion of water and sodium 3 h after instillation into the balloon occluded 'closed' jejunal segment (P less than 0.05 vs. controls). The rate of secretion was constant over the maximal period studied (4.5 h) and was similar to that reported in human cholera. None of the subjects experienced troublesome diarrhoea. We believe this model offers a relevant test system for assessing anti-diarrhoeal therapy in man.