Ion-exchange resins are commonly used to treat complications such as hyperkalemia, hyperphosphatemia, and hypercholesterolemia. Gastrointestinal complications may occur as side effects of such treatments. Sodium and calcium polystyrene sulfonate (PS-Ca) are cation-exchange resins comprising an insoluble structure that binds to potassium ions in the digestive tract and exchanges them with sodium and calcium ions, respectively, to promote their elimination. PS crystals are rhomboid, refractive, and basophilic in hematoxylin and eosin staining. To differentiate PS crystals from other ion-exchange resin crystals such as sevelamer and cholestyramine, periodic acid-Schiff, Ziehl-Neelsen, and Congo red staining are usually performed. Here, correlative light and electron microscopy (CLEM)-energy-dispersive X-ray spectroscopy and the NanoSuit method (CENM) was applied to perform a definitive identification of ion-exchange resins. CENM could detect sulfur in PS crystals without destroying the glass slides. Notably, PS retained its ion-exchange ability to bind potassium in paraffin sections. Differential diagnosis of anion-exchange resins, such as sevelamer and cholestyramine, was possible using these characteristics. The phosphorus:carbon ratio was higher in sevelamer than in cholestyramine after soaking paraffin sections in a phosphate solution. Therefore, CENM may be used for the differential pathological diagnosis of ion-exchange resins in paraffin sections.

Ion-exchange resins are commonly used to manage complications of chronic kidney disease, such as hyperphosphatemia, hyperkalemia, and hypercholesterolemia. Occasionally, these drugs can irritate the gastrointestinal lining and cause life-threatening intestinal necrosis. Currently, the pathophysiology of drug crystal-induced intestinal necrosis is not well understood. We hypothesized that crystals of ion-exchange resins like sevelamer, polystyrene sulfonate, and cholestyramine can trigger the formation of neutrophil and monocyte extracellular traps by contributing to intestinal barrier dysfunction. Light and fluorescence microscopy of the colonic resection specimen from a patient with chronic kidney disease revealed severe intestinal necrosis, ulceration, sevelamer crystals, and inflammation upon oral intake of sevelamer, as well as the formation of neutrophil extracellular traps in proximity to small sevelamer crystals. Indeed, drug crystals reduced metabolic activity and induced barrier dysfunction and cell death in human intestinal epithelial cells in vitro. In addition, drug crystals triggered the release of neutrophil and monocyte extracellular traps. Taken together, these data raise the possibility that besides other factors including chronic kidney disease, diabetes mellitus, and hypertension, drug crystals may further amplify a pre-existing barrier dysfunction and necroinflammation in a crescendo of local intestinal necrosis and systemic inflammation/infection, as occasionally observed in patients on ion-exchange resin therapy.

Pruritus is a common, troublesome symptom in patients with cholestatic liver diseases, especially frequent in intrahepatic cholestasis of pregnancy (ICP) and in primary biliary cholangitis (PBC). Cholestatic associated pruritus can have profound effects on the quality of life. The underlying mechanism is still poorly understood. Severe potential pruritogens have been discussed, such as bile salts, opioids, steroid and lysophosphatidic acid (LPA), but none of these are considered as key mediators. Because of this unraveling pathophysiology the treatment of hepatogenic pruritus often represents a clinical challenge. The EASL guidelines have suggested a step-wise approach, starting with elimination of pruritogens by bile acid sequestrants (cholestyramine), in second line managing the metabolism of pruritogens (rifampicin) and in third-line and fourth- line by modifying the itch perception with μ-opioid antagonist or selective serotonin reuptake inhibitors (SSRI). In treatment-refractory pruritus interruption of the enterohepatic cycle by molecular absorbent recirculating system (MARS), nasobiliairy drainage or experimental therapy such as Ultraviolet B light therapy can be considered. Liver transplantation may be reserved for intractable pruritus. Clinical trials with novel agents are ongoing, potentially providing efficacious options in the future.

This article considers the problem of estimating the average controlled direct effect (ACDE) of a treatment on an outcome, in the presence of unmeasured confounders between an intermediate variable and the outcome. Such confounders render the direct effect unidentifiable even in cases where the total effect is unconfounded (hence identifiable). Kaufman et al. (2005, Statistics in Medicine 24, 1683-1702) applied a linear programming software to find the minimum and maximum possible values of the ACDE for specific numerical data. In this article, we apply the symbolic Balke-Pearl (1997, Journal of the American Statistical Association 92, 1171-1176) linear programming method to derive closed-form formulas for the upper and lower bounds on the ACDE under various assumptions of monotonicity. These universal bounds enable clinical experimenters to assess the direct effect of treatment from observed data with minimum computational effort, and they further shed light on the sign of the direct effect and the accuracy of the assessments.

Hypocholesterolemic drugs may themselves increase (cholestyramine, CS) or decrease (lovastatin, Lov) peripheral tissue de novo cholesterol biosynthesis. This will alter the abundance of prenyl groups and potentially increase (CS) or decrease (Lov) K-ras membrane localization, with possible pro- or anti-carcinogenic effects (K-ras is a proto-oncogene frequently mutated in lung cancer). Female A/J, Swiss, and C57BL/6 mice were fed 2 or 4% CS, 1% niacin, or injected with Lov three (Lov-3x) or five (Lov-5x) times per week. After three weeks, serum cholesterol and triglycerides were determined enzymatically. Total, membrane, and cytoplasmic K-ras proteins were determined in lung homogenates by immunoprecipitation followed by Western blotting with a K-ras specific antibody. CS feeding increased membrane K-ras as hypothesized in A/J and C57BL/6 mice, but had no effect in Swiss mice. Lov failed in all three strains to reduce membrane K-ras, and resulted in an increase in total K-ras in A/J and C57BL/6 mice, while again lacking effect in Swiss mice. Niacin had no effect on K-ras protein in any mouse strain. These results differ from our published results for male mice of the same strains, particularly for A/J mice. Increased amounts of K-ras protein in the membrane fraction of A/J females (but not males) treated with either Lov or CS imply that if K-ras were to become mutated, CS could result in increased lung tumorigenesis and Lov would be less likely to be protective in females. In the light of these data, both sexes should be included in future animal and human chemoprevention trials.

Adult exposure to L-thyroxine has a wide range of presentations: most adults either do not develop symptoms or only become minimally symptomatic. Appropriate treatments after exposure to L-thyroxine have yet to be established. A 26-year-old woman with a suicidal intention was witnessed to ingest approximately 50 L-thyroxine tablets, each containing 0.1 mg L-thyroxine (total dose 5 mg). Cholestyramine was administered (4 g every 8 h p.o.). Vital signs were monitored every 6 h and the hormone levels (L-thyroxine and thyroid-stimulating hormone) every 24 h. The thyroxine levels increased, and the thyroid-stimulating hormone levels decreased, with a normalization of the L-thyroxine level on postingestion day 6. Hypertension, dysrhythmias, and delusions did not appear in our patient. Only distal tremor and diaphoresis appeared on day 1 after ingestion. Cholestyramine has been used in cases of iatrogenic hyperthyroidism, in patients with Graves' disease, and in patients with digoxin intoxications, with good responses in all cases and a low incidence of side effects. This case illustrates the potential utility of cholestyramine to treat L-thyroxine intoxications.

The human illness designated as possible estuarine-associated syndrome (PEAS) by the Centers for Disease Control and Prevention (CDC) has been associated with exposure to estuaries inhabited by toxin-forming dinoflagellates, including members of the fish-killing toxic Pfiesteria complex (TPC), Pfiesteria piscicida and Pfiesteria shumwayae. Humans may be exposed through direct contact with estuarine water or by inhalation of aerosolized or volatilized toxin(s). The five cases reported here demonstrate the full spectrum of symptoms experienced during acute and chronic stages of this suspected neurotoxin-mediated illness. The nonspecific symptoms most commonly reported are cough, secretory diarrhea, headache, fatigue, memory impairment, rash, difficulty in concentrating, light sensitivity, burning skin upon water contact, muscle ache, and abdominal pain. Less frequently encountered symptoms are upper airway obstruction, shortness of breath, confusion, red or tearing eyes, weakness, and vertigo. Some patients experience as few as four of these symptoms. The discovery that an indicator of visual pattern-detection ability, visual contrast sensitivity (VCS), is sharply reduced in affected individuals has provided an objective indicator that is useful in diagnosing and monitoring PEAS. VCS deficits are present in both acute and chronic PEAS, and VCS recovers during cholestyramine treatment coincident with symptom abatement. Although PEAS cannot yet be definitively associated with TPC exposure, resolution with cholestyramine treatment suggests a neurotoxin-mediated illness.

A potential therapy for antibiotic-associated pseudomembranous colitis is to bind Clostridium difficile toxins A and B using cholestyramine, a hydrophobic anion exchange medium. Frontal analysis in isotonic phosphate buffer was studied using post-column derivatization with o-phthalaldehyde, which gave a highly sensitive (> or =30 ng) flow-through analysis. Following load (1.5-3.0 microg toxin/3.6 mg), toxin A was bound at a slightly higher capacity than B, due to slower kinetics. A salt gradient eluted roughly 20% of bound toxin A with 0.6 M NaCl and toxin B with 1.1 M NaCl, hence toxin A showed weaker electrostatic affinity. The remainder of toxin A (65%) and some of toxin B (10% out of 50%) were eluted using a subsequent gradient to 60% acetonitrile in normal saline, which measured predominantly hydrophobic binding. Low and high affinity populations of both toxins were observed. Glycocholic acid or amino acids were competitive binders, although these components had little effect on the toxin A population bound primarily through ionic interactions. Competitive protein constituents in hamster cecal contents were also profiled. These results help to explain the variable clinical response in using cholestyramine to treat colitis. Using quaternary amine-polyhydroxymethacrylate (PHM) ion exchange chromatography, a trend for increased binding at higher pH was observed, especially for toxin A. Binding to strong cation exchange resins (sulfonate-PHM) was not observed. A range of reversed phase media retained both toxins, although recovery was very poor relative to protein standards. Size exclusion chromatography with light scattering detection showed that toxin B exists in different aggregation states, while toxin A remains monomeric.

Primary biliary cirrhosis (PBC) is a slowly progressive chronic cholestatic disease of the liver thought to be caused by immune destruction of the interlobular bile ducts. One-third of patients are asymptomatic and one-third of these develop symptoms within 5 years. Therapeutic regimens should be directed at the control of symptoms, prevention of complications and specific therapy aimed at controlling progression of the disease. Symptoms may be secondary to cholestasis or due to other associated diseases. The cause of pruritus secondary to cholestasis remains unknown; the anion exchange resin cholestyramine generally brings relief. In patients resistant or intolerant to this therapy, rifampin may be helpful, as well as ultraviolet light without sunblock. Liver transplantation may rarely be the only option for uncontrollable pruritus. Clinical manifestations of keratoconjunctivitis-sicca and xerostomia need constant attention to prevent corneal ulcers and dental caries. Preventative therapy includes regular screening for thyroid dysfunction and replacement therapy when necessary and the administration of the fat soluble vitamins A, D and K once hyperbilirubinaemia is present. Osteoporosis is a complication of all cholestatic liver disease. There is no satisfactory preventative therapy. It may be appropriate to give hormone replacement therapy to all post-menopausal women with PBC to reduce osteoporosis. Liver transplantation is the best option for those with fractures. Oesophageal varices may develop early in the course of PBC, non-selective beta-blocker therapy should be used as prophylaxis against variceal haemorrhage. The only specific therapy shown to cause both a biochemical and survival benefit in patients with PBC is ursodeoxycholic acid (UDCA). Treatment with UDCA delays progression, but does not result in a cure of this disease. Currently, liver transplantation is the only definitive treatment available for end-stage disease.

We report on a 17-year-old female patient with hyperlipidaemia, apoE2 homozygosity and characteristic dermatological features of type-III hyperlipoproteinaemia (HLP III). In contrast to the "classical" lipoprotein phenotype, with hypercholesterolaemia and hypertriglyceridaemia, in our case an elevated LDL cholesterol level was also present. To the best of our knowledge, this is the eleventh report in the literature of HLP III onset in a child or an adolescent. Treatment with several antilipidaemic drugs resulted only in a reduction of the serum triglyceride concentration, and not in an improvement of the hypercholesterolaemia or the elevated LDL cholesterol level. This therapeutic response was explained with reference to an uncommon association of the apoE2 homozygosity with the homo- or heterozygote state of familial hypercholesterolaemia. Another explanation for this phenomenon is the possible combination of the apoE2 homozygosity with a familial apolipoprotein-B 100 defect that has only recently come to light.

We report a 60-year-old man with intermittent diarrhea for 15 years which was worsened by cholecystectomy. The results of routine laboratory tests, x-ray studies of the gut, and endoscopy were normal. Fecal fat excretion was normal, but total bile acid excretion was increased in the alkaline feces. The retention of 75SeHCAT was low. Jejunal mucosal biopsy showed normal mucosa. Ileal biopsy was performed at ileoscopy some 10 to 15 cm proximal to the ileocecal valve. Scanning-electron and light microscopy showed a transitional zone between villous atrophy in the distal and normal mucosa in the proximal part of the biopsy specimen. The response of diarrhea to cholestyramine treatment was unequivocal, suggesting bile acid malabsorption. The increased enterohepatic cycling of bile acids after cholecystectomy may be responsible for a decrease in their ileal uptake. Very often, as in our patient, the diarrhea precedes cholecystectomy and is considerably increased by it. Cholecystectomy may unmask a previously unrecognized bile acid transport defect. In our patient, this defect might have been caused by the villous atrophy of the terminal ileum.

Sixty-one men with known hypercholesterolemia (plasma cholesterol greater than 265 mg/dl), most of whom were previous participants in the Coronary Primary Prevention Trial of the U.S. Lipid Research Clinic Program, were chosen to take part in this study to test the effectiveness of a new low-calorie (Questran Light) cholestyramine formulation against the proven effectiveness of the currently marketed formulation Questran in maintaining lowered plasma cholesterol levels. The study recorded changes in fasting plasma lipids, total cholesterol, high-density lipoprotein cholesterol, triglycerides, and calculated low-density lipoprotein cholesterol. After establishing baseline lipid/lipoprotein levels in a 3-week period during which all participants received the currently marketed formulation, the men were randomized into 2 groups, 1 group (n = 31) taking the new Questran Light formulation of 4 g of cholestyramine in 5 g of powder per pack, while the other group (n = 30) continued to take the marketed Questran formulation of 4 g of cholestyramine in 9 g of powder per pack. Each group consumed a total of 24 g/day of cholestyramine in 2 divided doses. At the end of the maintenance phase of the study there were no statistically significant mean changes in percentage from baseline to end-point lipid/lipoprotein levels within either group, nor were there any significant differences between the Questran Light group or the currently marketed Questran formulation group. The new low-calorie cholestyramine formulation appears to be equally as effective in maintaining lowered plasma cholesterol levels as the currently marketed formulation.