Clinical pharmacology and use of laxatives and lavage solutions

c-di-AMP modulates Listeria monocytogenes central metabolism to regulate growth, antibiotic resistance and osmoregulation

Cyclic diadenosine monophosphate (c-di-AMP) is a conserved nucleotide second messenger critical for bacterial growth and resistance to cell wall-active antibiotics. In Listeria monocytogenes, the sole diadenylate cyclase, DacA, is essential in rich, but not synthetic media and ΔdacA mutants are highly sensitive to the β-lactam antibiotic cefuroxime. In this study, loss of function mutations in the oligopeptide importer (oppABCDF) and glycine betaine importer (gbuABC) allowed ΔdacA mutants to grow in rich medium. Since oligopeptides were sufficient to inhibit growth of the ΔdacA mutant we hypothesized that oligopeptides act as osmolytes, similar to glycine betaine, to disrupt intracellular osmotic pressure. Supplementation with salt stabilized the ΔdacA mutant in rich medium and restored cefuroxime resistance. Additional suppressor mutations in the acetyl-CoA binding site of pyruvate carboxylase (PycA) rescued cefuroxime resistance and resulted in a 100-fold increase in virulence of the ΔdacA mutant. PycA is inhibited by c-di-AMP and these mutations prompted us to examine the role of TCA cycle enzymes. Inactivation of citrate synthase, but not down-stream enzymes suppressed ΔdacA phenotypes. These data suggested that c-di-AMP modulates central metabolism at the pyruvate node to moderate citrate production and indeed, the ΔdacA mutant accumulated six times the concentration of citrate present in wild-type bacteria.

Chemotherapy-Induced Constipation and Diarrhea: Pathophysiology, Current and Emerging Treatments

Gastrointestinal (GI) side-effects of chemotherapy are a debilitating and often overlooked clinical hurdle in cancer management. Chemotherapy-induced constipation (CIC) and Diarrhea (CID) present a constant challenge in the efficient and tolerable treatment of cancer and are amongst the primary contributors to dose reductions, delays and cessation of treatment. Although prevalence of CIC is hard to estimate, it is believed to affect approximately 16% of cancer patients, whilst incidence of CID has been estimated to be as high as 80%. Despite this, the underlying mechanisms of both CID and CIC remain unclear, but are believed to result from a combination of intersecting mechanisms including inflammation, secretory dysfunctions, GI dysmotility and alterations in GI innervation. Current treatments for CIC and CID aim to reduce the severity of symptoms rather than combating the pathophysiological mechanisms of dysfunction, and often result in worsening of already chronic GI symptoms or trigger the onset of a plethora of other side-effects including respiratory depression, uneven heartbeat, seizures, and neurotoxicity. Emerging treatments including those targeting the enteric nervous system present promising avenues to alleviate CID and CIC. Identification of potential targets for novel therapies to alleviate chemotherapy-induced toxicity is essential to improve clinical outcomes and quality of life amongst cancer sufferers.

Comparative Study of Three Regimens of Bowel Preparation Before Transabdominal Ultrasonography of the Colon

The objective of the study was to compare the efficacy of three bowel preparation regimens for transabdominal colon ultrasonography. A total of 192 consecutive patients were given one of three regimens (senna, magnesium sulfate or polyethylene glycol electrolyte powder) before ultrasonographic examinations. The cleaning grade (I = emptying; II = filled or filled + empty; III = I or II with some retention; and IV = retention [grades I and II were termed "qualified"]) and cleaning range (A = all seven colon sections were qualified; B = four to six sections were qualified; C = three or less sections were qualified) were evaluated retrospectively. Senna was found more effective than polyethylene glycol in terms of cleaning grade (p < 0.001), qualified rate (p < 0.001) and cleaning range (p = 0.003). Senna was better than magnesium sulfate in cleaning grade (p < 0.001). Our results suggest that senna seems to be the preferred regimen for bowel preparation before transabdominal colonic ultrasonography.

Predictors of Inadequate Bowel Preparation and Salvage Options on Colonoscopy

Inadequate bowel preparation is observed in more than 25% of all colonoscopies. Identification of predictive factors for inadequate colon cleaning is helpful and more detailed preparation methods should be used for patients at high risk. Age, male sex, inpatient status, and comorbidities were identified as independent risk factors in several previous studies. In patients with insufficient colon preparation, colon irrigation with endoscopic pumps or next-day colonoscopy following further bowel cleaning should be performed. In order to improve the efficacy and safety of both bowel preparation and colonoscopy, the endoscopic team should identify the patient’s medical conditions and choose the optimal bowel preparation agent and regimen.

Factors influencing quality of bowel preparation for colonoscopy

Recent technological advances in colonoscopy have led to improvements in both image enhancement and procedural performance. However, the utility of these technological advancements remain dependent on the quality of bowel preparation during colonoscopy. Poor bowel preparation has been shown to be associated with lower quality indicators of colonoscopy performance, such as reduced cecal intubation rates, increased patient discomfort and lower adenoma detection. The most popular bowel preparation regimes currently used are based on either Polyethylene glycol-electrolyte, a non-absorbable solution, or aqueous sodium phosphate, a low-volume hyperosmotic solution. Statements from various international societies and several reviews have suggested that the efficacy of bowel preparation regimes based on both purgatives are similar, although patients’ compliance with these regimes may differ somewhat. Many studies have now shown that factors other than the type of bowel preparation regime used, can influence the quality of bowel preparation among adult patients undergoing colonoscopy. These factors can be broadly categorized as either patient-related or procedure-related. Studies from both Asia and the West have identified patient-related factors such as an increased age, male gender, presence of co-morbidity and socio-economic status of patients to be associated with poor bowel preparation among adults undergoing routine out-patient colonoscopy. Additionally, procedure-related factors such as adherence to bowel preparation instructions, timing of bowel purgative administration and appointment waiting times for colonoscopy are recognized to influence the quality of colon cleansing. Knowledge of these factors should aid clinicians in modifying bowel preparation regimes accordingly, such that the quality of colonoscopy performance and delivery of service to patients can be optimised.

Hyperphosphatemia after sodium phosphate laxatives in low risk patients: prospective study

AIM

To establish the frequency of hyperphosphatemia following the administration of sodium phosphate laxatives in low-risk patients.

METHODS

One hundred consecutive ASA I-II individuals aged 35-74 years, who were undergoing colonic cleansing with oral sodium phosphate (OSP) before colonoscopy were recruited for this prospective study.

EXCLUSION CRITERIA

congestive heart failure, chronic kidney disease, diabetes, liver cirrhosis, intestinal obstruction, decreased bowel motility, increased bowel permeability, and hyperparathyroidism. The day before colonoscopy, all the participants entered a 24-h period of diet that consisted of 4 L of clear fluids with sugar or honey and 90 mL (60 g) of OSP in two 45-mL doses, 5 h apart. Serum phosphate was measured before and after the administration of the laxative.

RESULTS

The main demographic data (mean +/- SD) were: age, 58.9 +/- 8.4 years; height, 163.8 +/- 8.6 cm; weight, 71 +/- 13 kg; body mass index, 26 +/- 4; women, 66%. Serum phosphate increased from 3.74 +/- 0.56 to 5.58 +/- 1.1 mg/dL, which surpassed the normal value (2.5-4.5 mg/dL) in 87% of the patients. The highest serum phosphate was 9.6 mg/dL. Urea and creatinine remained within normal limits. Post-treatment OSP serum phosphate concentration correlated inversely with glomerular filtration rate (P < 0.007, R(2) = 0.0755), total body water (P < 0.001, R(2) = 0.156) and weight (P < 0.013, R(2) = 0.0635).

CONCLUSION

In low-risk, well-hydrated patients, the standard dose of OSP-laxative-induced hyperphosphatemia is related to body weight.

Adverse renal and metabolic effects associated with oral sodium phosphate bowel preparation

Colorectal cancer can be prevented by the removal of adenomatous polyps during screening colonoscopy, but adequate bowel preparation is required. Oral sodium phosphate (OSP), an effective bowel purgative, is available over the counter and requires a substantially lower volume than polyethylene glycol-based preparative agents. Accumulating reports implicate OSP in electrolyte disturbances as well as acute kidney injury (AKI) in a syndrome termed phosphate nephropathy (a form of nephrocalcinosis). Despite published case reports and case series, the actual incidence, risk factors, and natural history of phosphate nephropathy remain largely undefined. Several recent observational studies have provided new information on these important issues while supporting a link between OSP and acute phosphate nephropathy as well as the development of chronic kidney disease in elderly patients, many of whom had a normal serum creatinine at the time of OSP ingestion. This review summarizes current knowledge about the renal complications of OSP, risk factors for its development, and the pathophysiology of acute and chronic kidney damage in nephrocalcinosis.

Acute phosphate nephropathy--an emerging issue

Acute phosphate nephropathy is an accepted complication of the use of phosphate preparations in patients about to undergo colonoscopy. Age, renal failure, and the ongoing use of medications, such as angiotensin-converting enzyme inhibitors and/or angiotensin-receptor blockers, are now recognized as risk factors for the development of phosphate nephropathy. The presence of any of these risk factors necessitates careful attention to avoiding excessive dehydration in the process of bowel cleansing. In so doing, the likelihood of acute phosphate nephropathy occurring can be lessened.

Dosing considerations in the use of sodium phosphate bowel preparations for colonoscopy

OBJECTIVE

To review dosing considerations and other treatment recommendations to maximize the efficacy, tolerability, and safety of sodium phosphate (NaP) preparations.

DATA SOURCES

Literature was accessed through PubMed (1990-May 2007) and abstracts from scientific meetings.

STUDY SELECTION AND DATA EXTRACTION

English-language publications including clinical trials and case reports were evaluated. Recent reports assessing newer bowel preparations containing reduced doses of NaP were reviewed to evaluate efficacy, tolerability, and safety.

DATA SYNTHESIS

Among commonly administered bowel preparations for colonoscopy, NaP preparations are generally more effective and better tolerated compared with polyethylene glycol electrolyte lavage solution regimens. However, NaP preparations are contraindicated in specific patient populations, and clinicians must use effective screening mechanisms to select proper patients to receive NaP preparation for colonoscopy. Recently, cases of renal failure in patients with previously normal renal function have been reported after NaP preparation for colonoscopy, heightening concerns about the safety of these agents. Newer products contain reduced doses of NaP and may improve the safety and tolerability of NaP purgatives without compromising efficacy of colon cleansing. In addition, accumulating clinical data and/or rationale support split dosing of NaP products, wide intervals between doses, and aggressive hydration before and during bowel preparation and after the colonoscopy procedure.

CONCLUSIONS

Safe administration of NaP products requires rigorous attention to dosing considerations and other treatment recommendations, including administration of minimally effective doses of NaP, split-dosing schedules, and aggressive hydration.

Gastroesophageal reflux disease in a low-income region in Turkey

OBJECTIVES

Detailed population-based data regarding the prevalence and symptom profile of gastroesophageal reflux disease (GERD) in underdeveloped and developing Caucasian countries are lacking. The aim of this study was to determine the prevalence and clinical spectrum of GERD in a low-income region in Turkey.

METHODS

We used a previously validated reflux questionnaire, which was translated into Turkish and culturally adapted. The questionnaire was applied to 630 randomly selected participants greater than 20 yr old living in a population of 8,857 adults, with a low mean income of 75 dollars/person/month. The reliability and reproducibility of the questionnaire were calculated using the kappa statistic (test-retest). Endoscopy and/or 24-h intraesophageal pH monitoring were used to ascertain its validity in identifying patients with reflux.

RESULTS

The prevalence of GERD symptoms was 10% for heartburn, 15.6% for regurgitation, and 20% for either symptom experienced at least weekly (95% CI). Heartburn and regurgitation were associated with noncardiac chest pain (37.3%), dysphagia (35.7%), dyspepsia (42.1%), odynophagia (35.7%), globus, hoarseness, cough, hiccup, nausea, vomiting, belching, and NSAID use, but not with body mass index in both frequent and occasional symptom groups. The prevalence of heartburn symptoms, but not regurgitation, increased significantly with age.

CONCLUSIONS

The prevalence of GERD in a low-income population in Turkey was similar to that of developed countries, although with a different symptom profile, namely, a lower incidence of heartburn and a higher incidence of regurgitation and dyspepsia. These findings support the contention that there are a large number of patients worldwide in underdeveloped nations with poorly recognized and largely undertreated GERD.

Safety Issues Regarding Colonic Cleansing for Diagnostic and Surgical Procedures

There are various methods available to cleanse the colon in preparation for diagnostic and surgical procedures. The popular options are diet and cathartic regimens, gut lavage and phosphate preparations. Each method has its own unique characteristics and safety profile. Diet and cathartic regimens are based on traditional methods of colonoscopy preparation and remain an acceptable and safe alternative for patients unwilling or unable to tolerate other bowel preparations. Gut lavage methods involve ingestion of 2-4L of osmotically balanced solutions containing polyethylene glycol, which have been shown to be safe and effective for colon cleansing, including for special patient populations with cardiac, renal or hepatic dysfunction. Phosphate preparations have also been shown to be safe and effective for colon cleansing and are generally better tolerated than counterpart gut lavage solutions. However, this method has safety concerns for some patients with cardiac, renal and hepatic dysfunctions.

Women's colonic digestive health

Digestive problems in women are common and sometimes debilitating. Twenty percent of women suffer from irritable bowel syndrome, 20% have constipation, and all American women will need screening for colon cancer, the number two cause of cancer death in women. This article reviews management of these disorders as well as lower gastrointestinal symptoms associated with menses, hysterectomy, fecal incontinence, and rectal bleeding.

Adverse effects of laxatives

Laxatives are among the most commonly used drugs or additives. Most are quite safe when used judiciously, intermittently when possible, and in the absence of contraindications. Bulking agents and nonabsorbable compounds such as lactulose can cause bloating but have very few serious adverse effects except for the allergic reaction to psyllium preparations. Osmotic laxatives containing poorly absorbable ions such as magnesium or phosphate can cause metabolic disturbances, particularly in the presence of renal impairment. However, if taken intermittently, in the absence of conditions such as ileus or bowel obstruction, they have few adverse effects. Polyethylene glycol solutions are emerging as an effective and safe mode of treatment for chronic constipation. Of stimulant laxatives, senna compounds and bisacodyl are the most commonly used. Although there are data to support the neoplastic potential of this class of drugs in in vitro studies, epidemiologic data in humans so far has not established a clear link between these laxatives and colonic neoplasia. The link between stimulant laxatives and structural changes, such as the "cathartic colon" or enteric nerve damage, is not well established either. Danthron compounds should be avoided because of hepatotoxicity.

Pathophysiology and management of bowel dysfunction in multiple sclerosis

The prevalence of bowel dysfunction in multiple sclerosis (MS) patients is higher than in the general population. Up to 70% of patients complain of constipation or faecal incontinence, which may also coexist. This overlap can relate to neurological disease affecting both the bowel and the pelvic floor muscles, or to treatments given. Bowel dysfunction is a source of considerable ongoing psychosocial disability in many patients with MS. Symptoms related to the bladder and the bowel are rated by patients as the third most important, limiting their ability to work, after spasticity and incoordination. Bowel management in patients with MS is currently empirical. Although general recommendations include maintaining a high fibre diet, high fluid intake, regular bowel routine, and the use of enemas or laxatives, the evidence to support the efficacy of these recommendations is scant. This review will examine the current state of knowledge regarding the pathophysiological mechanisms underlying bowel dysfunction in MS, outline the importance of proper clinical assessment of constipation and faecal incontinence during the diagnostic work-up, and propose various management possibilities. In the absence of clinical trial data on bowel management in MS, these should be considered as a consensus on clinical practice from a team specialized in bowel dysfunction.

Slow transit constipation

Slow transit constipation is a clinical syndrome predominantly affecting young women, characterized by constipation and delayed colonic transit, occasionally associated with pelvic floor dysfunction. The disorder spans a spectrum of variable severity, ranging from patients who have relatively mild delays in transit but who are otherwise indistinguishable from irritable bowel syndrome patients at one extreme, to patients with colonic inertia or chronic megacolon at the other extreme. Potential mechanisms for impaired colonic propulsion include fewer colonic HAPCs or a reduced colonic contractile response to a meal. The cause of the syndrome is unclear. The treatment is primarily medical; surgery is reserved for patients with severe disease or colonic inertia. Recognition and treatment of pelvic floor dysfunction is crucial for patients treated medically or surgically. Collaborative studies are necessary to determine the pathophysiology of this disorder and to ascertain the efficacy of novel prokinetic agents.