Sucralfate, intestinal aluminum absorption, and aluminum toxicity in a patient on dialysis

Drug-Dosing Adjustment in Dogs and Cats with Chronic Kidney Disease

Chronic kidney disease is a common kidney disorder in adult and aged dogs and cats; the management of associated complications and comorbidities generally requires a life-long medical treatment to ensure a good quality of life of affected patients. However, indications and the literature on drug dosing in dogs and cats with chronic kidney disease are often lacking. The aim of this review is to revise the current literature on drug dosing in canine and feline patients with renal impairment, with a special focus on the most commonly used medications to manage chronic kidney disease and possible comorbidities.

ACVIM consensus statement: Support for rational administration of gastrointestinal protectants to dogs and cats

The gastrointestinal (GI) mucosal barrier is continuously exposed to noxious toxins, reactive oxygen species, microbes, and drugs, leading to the development of inflammatory, erosive, and ultimately ulcerative lesions. This report offers a consensus opinion on the rational administration of GI protectants to dogs and cats, with an emphasis on proton pump inhibitors (PPIs), histamine type-2 receptor antagonists (H2 RAs), misoprostol, and sucralfate. These medications decrease gastric acidity or promote mucosal protective mechanisms, transforming the management of dyspepsia, peptic ulceration, and gastroesophageal reflux disease. In contrast to guidelines that have been established in people for the optimal treatment of gastroduodenal ulcers and gastroesophageal reflux disease, effective clinical dosages of antisecretory drugs have not been well established in the dog and cat to date. Similar to the situation in human medicine, practice of inappropriate prescription of acid suppressants is also commonplace in veterinary medicine. This report challenges the dogma and clinical practice of administering GI protectants for the routine management of gastritis, pancreatitis, hepatic disease, and renal disease in dogs and cats lacking additional risk factors for ulceration or concerns for GI bleeding. Judicious use of acid suppressants is warranted considering recent studies that have documented adverse effects of long-term supplementation of PPIs in people and animals.

Science review: The use of proton pump inhibitors for gastric acid suppression in critical illness

Prophylaxis is routinely provided for critically ill patients admitted to intensive care units (ICUs) who are at high risk for stress-related mucosal damage (SRMD), an erosive process of the gastroduodenum associated with abnormally high physiological demands. Traditionally, treatment options have included sucralfate, antacids and histamine H2 receptor antagonists (H₂RAs). The H₂RAs are currently the most widely used agents in prophylactic acid suppression; however, proton pump inhibitors (PPIs) have recently replaced H₂RAs in the treatment of many acid-related conditions. PPIs achieve a more rapid and sustained increase in gastric pH and are not associated with the rapid tachyphylaxis seen with H₂RAs. As a result, and after the introduction of intravenous formulations, PPIs are beginning to be used for the prophylaxis of SRMD in critically ill adults. The high prevalence of renal and hepatic impairment among the ICU population, as well as the need for multiple drug therapy in many patients, means that pharmacokinetic characteristics and the potential for drug interactions may be important considerations in the choice of prophylactic agent. This review seeks to present the pharmacological evidence that may inform decision-making about the prescription of drugs for prophylaxis of SRMD.

Aluminum accumulation in critically ill children on sucralfate therapy

BACKGROUND: Sucralfate, used in stress ulcer prophylaxis, contains aluminum, which can be absorbed from the gut. OBJECTIVE: To determine whether toxic serum aluminum levels can develop after short-term sucralfate therapy in critically ill children. DESIGN: Retrospective clinical study. SETTING: Pediatric intensive care unit of a pediatric university hospital. PATIENTS: Nineteen patients receiving mechanical ventilatory support (median age, 5 yrs [range, 0.25-16 yrs]; median weight, 17 kg [range, 3.5-60 kg]). INTERVENTIONS: All patients received sucralfate suspension nasogastrically. Measurements and RESULTS: Serum aluminum concentrations were measured after a short period on sucralfate therapy (median time, 7 days [range, 3-14 days]). There was no correlation between total sucralfate dose received (p =.35) or dose of sucralfate per unit of body weight (p =.55) and serum aluminum. Nine patients received peritoneal dialysis. Serum aluminum levels were higher in the nine patients who received peritoneal dialysis (median aluminum concentration, 2.86 &mgr;mol/L [range, 0.19-12.3 &mgr;mol/L]) than the ten patients not dialyzed (median aluminum concentration, 0.55 &mgr;mol/L [range, 0.18-0.94 &mgr;mol/L]) (p =.001). The peak serum creatinine levels were higher in the dialyzed patients (median creatinine level, 500 &mgr;mol/L [range, 163-910 &mgr;mol/L]) than those not dialyzed (median creatinine level, 98 &mgr;mol/L [range, 36-415 &mgr;mol/L]) (p =.006). There was a trend toward correlation between peak serum creatinine and serum aluminum (p =.06). CONCLUSION: Aluminum accumulation occurs in children with acute renal failure on sucralfate, especially those receiving dialysis. If sucralfate is used in children in renal failure, serum aluminum concentrations should be monitored regularly.

Use of sucralfate in renal failure

OBJECTIVE

To assess the potential for the development of aluminum toxicity in patients with renal insufficiency or chronic renal failure who are taking sucralfate.

DATA SOURCES

Clinical literature accessed through MEDLINE (1966-December 1999) and International Pharmaceutical Abstracts (1970-December 1999). Key search terms included sucralfate, renal failure, renal insufficiency, and end-stage renal disease.

DATA SYNTHESIS

Urinary excretion is an important route of elimination for systemically absorbed aluminum. Accumulation of aluminum in patients with impaired renal function may lead to significant toxicity. A potential source of aluminum is the antiulcer medication sucralfate. Studies and case reports evaluating the use and toxicity of sucralfate in patients with normal renal function, as well as those with renal failure or renal insufficiency, were reviewed.

CONCLUSIONS

Aluminum accumulation and toxicity have been reported with the use of sucralfate in patients with compromised renal function. The risk of toxicity most likely represents a long-term complication of sucralfate use in this patient population. Toxicity may be enhanced by concurrent use of other aluminum-containing medications, such as phosphate binders or antidiarrheal preparations. These medications, in addition to sucralfate, should be avoided if possible in patients with end-stage renal disease. Patients with renal failure or renal insufficiency who are undergoing prolonged sucralfate therapy should be monitored for potential signs of aluminum toxicity.

Plasma aluminum levels during sucralfate prophylaxis for stress ulceration in critically ill patients on continuous venovenous hemofiltration: a randomized, controlled trial

OBJECTIVE

To investigate plasma aluminum levels in critically ill patients requiring continuous venovenous hemofiltration (CVVH), while receiving sucralfate for stress ulcer prophylaxis.

DESIGN

Randomized, controlled study.

SETTING

Cardiothoracic intensive care unit.

PATIENTS

Twenty postoperative cardiac surgical patients

INTERVENTIONS

Twenty patients requiring CVVH support for acute renal failure were randomized into two groups for concurrent stress ulcer prophylaxis. Group 1 (n = 10) received nasogastric sucralfate, and group 2 patients received intravenous ranitidine. Plasma aluminum samples were analyzed at baseline and on days 1, 4, 8, and 14.

MEASUREMENTS AND MAIN RESULTS

In both the sucralfate and ranitidine groups, clinical characteristics, number of days the patients were on CVVH support (median, 5.5 [range, 2-32] days, and median, 3 [range, 2-18] days, respectively) and duration of prophylaxis (median, 12 [range, 4-42] days, and median, 16 [range, 3-62] days, respectively) were similar. There were no significant differences in the baseline aluminum concentrations (median, 0.37 [range, 0.15-1.63] micromol/L, vs. median, 0.32 [range, 0.11-1.0] micromol/L; p =.79). On initiation of therapy, aluminum levels in the sucralfate group increased dramatically on day 1 (median, 0.87 [range, 0.26-4.4] micromol/L) and peaked on day 4 (median, 2.84 [range, 1.52-4.44] micromol/L) with seven of the ten patients exhibiting levels of >2 micromol/L. In the ranitidine group, there were no significant elevations in aluminum levels above baseline. Analysis of the two groups at the four time points revealed that aluminum levels in the sucralfate group were up to 14 times higher, with the confidence intervals suggesting that the true value may be 2-27 times higher (p <.0001). On cessation of CVVH, a rapid decline in aluminum levels was observed. No clinical manifestations of these potentially toxic levels were observed.

CONCLUSIONS

The use of sucralfate for stress ulcer prophylaxis in patients requiring CVVH results in toxic elevations in plasma aluminum levels. Alternative agents should be considered for prophylaxis in these patients.

Acute gastrointestinal bleeding in the intensive care unit. The gastroenterologist's perspective

Although SRES-associated hemorrhage previously constituted a significant cause of bleeding in the ICU, improvements in ICU management and the institution of prophylactic measures in high-risk patients have significantly reduced SRES-associated hemorrhage since the 1980s. Antacids, H2-receptor antagonists, and sucralfate have been shown to be effective in preventing clinically significant bleeding resulting from SRES, particularly when the intragastric pH is maintained at greater than 4. A selective approach should be adopted in SRES prophylaxis: Patients on mechanical ventilation, with coagulopathy, or with two of the other known risk factors should receive prophylaxis. Although the drug of choice depends to some extent on local preferences, an H2-receptor antagonist by continuous intravenous infusion may represent the best option. No pharmacologic therapy is of proven value once hemorrhage begins, but the current interventional techniques are effective in controlling hemorrhage. Gastrointestinal bleeding from NOMV has become less common with improvements in the hemodynamic monitoring of critically ill patients, but this disease must always be considered when lower gastrointestinal bleeding occurs in the context of relative hypoperfusion. For SRES and NOMV, treatment of the underlying disease or diseases is the optimal route to prevention.

Stress ulcer prophylaxis in medical ICU patients: annual utilization in relation to the incidence of endoscopically proven stress ulceration

OBJECTIVE

To measure changes in the proportion of medical intensive care unit (MICU) patients prescribed pharmacologic stress ulcer prophylaxis therapy over a 4-year period in relation to the incidence of stress-related ulceration detected by endoscopy at our institution.

DESIGN

Retrospective 4-year review of pharmacy and endoscopy databases.

SETTING

A 35-bed MICU.

PATIENTS

Patients (n = 2941) admitted to the MICU for longer than 24 hours, between January 1, 1993, and December 31, 1996, without acute gastrointestinal hemorrhage on admission.

METHODS

Records were reviewed to identify patients prescribed pharmacologic stress ulcer prophylaxis (> 24 h of sucralfate or a histamine2-receptor antagonist [H2RA]), and patients with evidence of stress ulceration during endoscopy.

RESULTS

The number of patients per year receiving stress ulcer prophylaxis significantly (p < 0.001) decreased between 1993 and 1996: 1993, 492/693 (71%); 1994, 478/798 (60%); 1995, 295/670 (44%); 1996, 164/780 (21%). There was no difference between years in the median duration of stress ulcer prophylaxis therapy or the proportion of patients receiving sucralfate versus H2RA therapy. There was no difference (p = 0.91) between years in the annual incidence of definite or possible stress-related ulceration: 1993, 6/693 (0.87%); 1994, 5/798 (0.63%); 1995, 6/670 (0.90%); 1996, 5/780 (0.64%).

CONCLUSIONS

The incidence of endoscopically proven stress-related ulceration has remained unchanged over the past 4 years in our MICU despite significantly fewer patients receiving pharmacologic stress ulcer prophylaxis therapy.

Gastrointestinal diseases in women

Gastrointestinal disorders are among the most common disorders for which women seek medical attention. Most gastrointestinal diseases in women are not inherently different from those that occur in men. There are several disorders, however, that occur more frequently or manifest themselves differently in women. This article reviews common gastrointestinal disorders affecting women. The pathophysiology, clinical manifestations, management, and gender-specific issues of gastroesophageal reflux disease, peptic ulcer disease, irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD) are discussed.

Influence of intravenously administered ciprofloxacin on aerobic intestinal microflora and fecal drug levels when administered simultaneously with sucralfate

Ciprofloxacin, when given intravenously (i.v.), is secreted in significant amounts via the mucosa into the intestinal lumen. Sucralfate inhibits the antimicrobial activity of ciprofloxacin. The effect of combined therapy on the intestinal flora was investigated in 16 healthy volunteers. They were randomly assigned to two groups. Group A received 2 g of sucralfate orally three times a day for 7 days and 400 mg of ciprofloxacin i.v. twice a day (b.i.d.) starting 3 days after the sucralfate administration began. Group B was given only 400 mg of ciprofloxacin i.v. b.i.d. for 4 days. A total of 9 stool samples were collected from each subject beginning the week before ciprofloxacin was administered and on days -1, 1, 2, 3, 4, 7, 9, and 10 or 11 after commencement of the infusion period. The aerobic fecal flora was determined by standard microbiological methods. Measurements of fecal ciprofloxacin levels were based on high-performance liquid chromatography. Counts of bacteria of the family Enterobacteriaceae decreased in all subjects and were below 10(2) CFU/g in eight of eight subjects (group A) and six of eight subjects (group B) on day 4, but they returned to normal in all but one subject (group A) 10 days after the last infusion. The decreases in levels of bacteria of the family Enterobacteriaceae were not significantly different in groups A and B (Kaplan-Meier test). Staphylococci and nonfermenters responded variably, enterococci and lactobacilli remained unchanged, and candida levels increased transiently in four subjects (two in each group). Maximum fecal drug levels ranged from 251 to 811 microg/g. No significant difference could be found between the two groups. The i.v. application of ciprofloxacin eliminates intestinal bacteria of the family Enterobacteriaceae in a rapid and selective manner. This effect is not affected by simultaneous oral application of sucralfate.

Epidemic aluminum intoxication in hemodialysis patients traced to use of an aluminum pump

This study was designed to identify the source, risk factors, and clinical consequences of an outbreak of aluminum intoxication in hemodialysis patients using case-control and cohort studies. In 1991, a dialysis center in Pennsylvania [Dialysis Center A (DCA)] identified a number of patients with elevated serum aluminum levels. All patients receiving dialysis at DCA during January 1, 1987 to March 26, 1992 were involved in the study. A case-patient was defined as any patient with a serum aluminum level > or = 100 micrograms/liter after > or = 5 dialysis sessions at DCA. Fifty-nine case-patients were identified. Risk factors for elevated serum aluminum levels were receipt of bicarbonate- (rather than acetate-) based dialysate, higher number of sessions using bicarbonate dialysis, receipt of acid concentrate (used in bicarbonate dialysis) passed through one of two electric pumps, and a greater number of sessions using this concentrate. The electric pumps had an aluminum casing, casing cover, and impeller. Elevated levels of aluminum were found in acid concentrate after passing through a pump. Seizures and mental status changes requiring hospitalization were associated with aluminum exposure. We found that epidemic aluminum intoxication was caused by the use of an electric pump with aluminum housing to deliver acid concentrate used in bicarbonate dialysis. This outbreak demonstrates why it is essential to insure that all fluid pathways, storage tanks, central delivery systems, and pumps are compatible with low pH fluids before converting from acetate to bicarbonate dialysis.

Pharmacokinetic optimisation of the treatment of peptic ulcer in patients with renal failure

The pathogenesis of peptic ulceration is not yet clear. It could be due to an imbalance between acid secretion and mucosal defensive and/or protective mechanisms, but the association between Helicobacter pylori and peptic ulceration has questioned this hypothesis. Therefore, drugs inhibiting acid secretion and/or eradicating H. pylori are of major interest. Peptic ulcer disease is often associated with renal failure. For the selection of the proper dosage of these agents their pharmacokinetic properties and alterations in pharmacokinetics in various disease states, including renal failure, should be known. As histamine H2-receptor antagonists and pirenzepine are mainly eliminated by the renal route their elimination is dependent on creatinine clearance. Consequently, their elimination will be impaired in patients with renal insufficiency, which makes dosage reduction mandatory in these patients. No dosage supplementation is necessary after any type of dialysis because the drugs are removed in insignificant amounts by the various blood purification procedures. Misoprostol and proton pump inhibitors, such as omeprazole, lansoprazole and pantoprazole, are primarily eliminated by nonrenal routes. Therefore no dosage adjustments are necessary in patients with renal insufficiency. Bismuth salts, sucralfate and antacids should be avoided in patients with renal failure because of the accumulation of their cations and the associated risk of toxic reactions. For most agents more long term experience from comparative and double-blinded studies is needed to define better their clinical efficacy and tolerability in patients with renal failure.

Changing perspectives of stress gastritis prophylaxis

OBJECTIVE

To present recent advances in stress gastritis prophylaxis in the critically ill and review considerations in selection of a prophylactic agent.

DATA SOURCES

Information was obtained from MEDLINE search, reference lists from articles identified in search, and from review articles.

STUDY SELECTION

Emphasis was placed on controlled trials conducted within the last 5 years.

DATA EXTRACTION

All literature was assessed for methodology, results, and conclusions. Results of prospective, randomized trials, and meta-analyses are summarized.

DATA SYNTHESIS

Histamine2-receptor antagonists, antacids, and sucralfate appear equally effective in preventing stress gastritis in the critically ill. A definitive cause-effect relationship between histamine2-receptor antagonists and increased incidence of nosocomial pneumonia has not yet been established. The indications for using a prophylactic agent and consideration in selecting an agent should include an evaluation of the following: risk factors for gastritis including the type of intensive care patient, comparative efficacy, adverse effects, drug interactions, cost, and ease of administration. The least expensive, safest agent requiring minimal monitoring is sucralfate. Prevention of stress gastritis has never been shown to reduce morbidity or mortality significantly.

CONCLUSIONS

Controversies still exist regarding the need to provide prophylaxis, the choice of an agent, and the relative importance of previously identified risk factors. Further well-designed studies are needed before consensus can be reached.

Bone disease in burn patients

Burn patients are at risk for bone disease due to aluminum (Al) exposure from use of antacids and albumin, partial immobilization, and increased production of endogenous glucocorticoids. Moreover, severely burned children are growth impaired up to 3 years after the burn. To determine the extent of bone disease, we studied nine men and three women, ages 18-41 years, with greater than 50% body surface area burn. Seven patients underwent iliac crest bone biopsy following double tetracycline labeling, one additional patient expired after a single label, and three others had postmortem specimens obtained for quantitative Al only. Serial serum and urine samples were obtained weekly until biopsy or death. All biopsied patients had reduced bone formation and osteoid area, surface, and width, with mineral apposition rate, osteoblast surface, and osteoclast number with normal eroded surfaces compared to age- and sex-matched normal ambulatory volunteers. Burn patients also had reduced bone formation, mineral apposition rate, osteoid area, and surface compared to age-matched volunteers at short-term bed rest. Serum levels of osteocalcin were low. Most patients had mild hypercalcemia but only a third had hypercalciuria. All patients had elevated Al in blood or urine; urine Al correlated inversely with serum osteocalcin. In 60% significant bone Al was detectable by stain or quantitation. Our data are compatible with burn patients having markedly reduced bone turnover. Al loading, partial immobilization, endogenous corticosteroids, and cytokine production may be among the etiologic factors.

Renal effects of peptic ulcer therapy

Drugs used in the treatment of peptic ulcer disease may interact with the renal system in a variety of ways. Since many agents are eliminated by renal excretion, clearance of these agents may be reduced and half-life extended in the presence of renal insufficiency. The histamine H2-receptor antagonists may interfere with renal tubular excretion of creatinine and cationic drugs, resulting in elevated serum concentrations and reduced renal clearance. The prostaglandin E1 analogue misoprostol is used as a cytoprotective agent but has renal effects. The renal effects differ between systems studied. In the rat, misoprostol reduces cyclosporin-induced renal tubular toxicity, whereas in humans it has been shown to attenuate renal allograft rejection. Sucralfate is the aluminium salt of sucrose octasulfate. It permits the absorption of aluminium in amounts similar to aluminium-containing antacids, and toxicity has been demonstrated in the presence of renal insufficiency. Bismuth compounds are used increasingly to treat peptic ulcer disease, and bismuth toxicity has been described in association with renal insufficiency. Aluminium-, calcium- and magnesium-containing antacids are used as oral phosphate binders in patients with renal insufficiency in addition to their usual indications. Cation absorption and accumulation with all of these antacid preparations has been described and may lead to toxicity.

Aluminum absorption and excretion following sucralfate therapy in chronic renal insufficiency

PURPOSE

To measure serum aluminum levels and urinary aluminum excretion in patients with chronic renal insufficiency (CRF) receiving therapeutic doses of sucralfate.

PATIENTS

Six patients with CRF were enrolled in the study. Creatinine clearances ranged from 0.2 to 0.9 mL/second (mean +/- SD 0.40 +/- 0.25 mL/second). Seven subjects with normal renal function were also studied.

METHODS

Each subject received sucralfate 1 g four times daily for 21 days. Serum and urine samples (serum only) were collected on baseline and on Days 2, (3), 8, 15, 22, (23, 24), 29, and 36. Samples were assayed by graphite furnace atomic absorption spectrophotometry.

RESULTS

In CRF, serum aluminum levels (mumol/L) increased by Day 2 and remained elevated to Day 24. Urinary aluminum excretion (mumol/day) was elevated throughout the study. The elimination half-life of serum aluminum after therapeutic dosing of sucralfate was 13.1 +/- 3.1 days. In subjects with normal renal function, baseline serum aluminum levels were similar to those in CRF (0.12 +/- 0.12 versus 0.11 +/- 0.12 mumol/L), but serum aluminum levels were higher at the end of the study in CRF (Day 22, 0.24 +/- 0.17 versus 0.83 +/- 0.48 mumol/L).

CONCLUSIONS

After therapeutic doses of sucralfate, significant elevations of serum aluminum levels occurred in CRF. Serum aluminum levels were higher in patients with CRF than in normal subjects. Long courses of sucralfate should be used with caution or avoided in CRF.

Medical Therapy of Peptic Ulcer Disease

The gastric duodenal mucosa normally is protected from the damaging effects of gastric acid and pepsin by ill-defined mechanisms. Ulcers may arise when there is an imbalance between the aggressive and defensive factors that renders the mucosa susceptible to damage. A variety of factors have been identified that may favor the development of peptic ulcers, but no single pathophysiologic defect applies in all ulcer patients. In duodenal ulcers, gastric acid hypersecretion is observed in as many as one third of patients; however, most patients with duodenal ulcers secrete normal amounts of gastric acid. Decreased mucosal bicarbonate secretion may be important in at least some duodenal ulcer patients. Use of NSAIDs may cause either gastric or duodenal ulcers, probably through the inhibition of mucosal prostaglandin synthesis and disruption of mucosal defenses. Finally, a recently identified bacterium, H. pylori, causes a chronic gastritis that is found in the overwhelming majority of patients with duodenal ulcers and non-NSAID-associated gastric ulcers. This bacterium may play a pivotal role in ulcer pathogenesis and, especially, in ulcer recurrences. A number of drugs of proved efficacy are available for the treatment of acute duodenal and gastric ulcers. The H2 receptor antagonists administered once daily remain the mainstay of ulcer therapy because of their efficacy, ease of use, and excellent safety profile. More thorough and long-lasting acid inhibition is afforded by the H+/K(+)-ATPase inhibitor omeprazole. This agent also promotes more rapid ulcer healing, but in most patients, this minor advantage may not justify the higher cost. It is not known whether more rapid healing will translate into lower ulcer complication rates. Until further data are available, this drug may be preferable in patients with large or complicated ulcers. In patients with refractory ulcers, omeprazole is clearly superior to other available agents. Agents that promote mucosal defense mechanisms are becoming increasingly popular in the treatment of duodenal ulcers but have undergone less testing than in gastric ulcers. Sucralfate 1 g four times daily is equivalent to H2 antagonists in the treatment of duodenal ulcers and, probably, gastric ulcers. Its requirement for multiple daily doses makes it somewhat less attractive at present to most patients. Low- to medium-dose Al-containing antacids are inexpensive and efficacious in duodenal ulcer therapy. They should remain as therapeutic options for the compliant patient in whom cost considerations are important. Colloidal bismuth subcitrate 120 mg four times a day is comparable to other agents in the acute treatment of duodenal ulcers and likely gastric ulcers.(ABSTRACT TRUNCATED AT 400 WORDS)

Practical pharmacology and cost-effective management of peptic ulcer disease

The clinical approach to the therapy of peptic ulcer disease has changed over the years as our understanding of its pathogenesis has grown. No longer is excess acid production seen as the single cause of ulcer disease; rather, its pathogenesis is viewed as the disturbance of a complex balance of ulcerogenic and protective factors. Today, the clinician's aim is to restore the balance between protective and aggressive factors. Simultaneously, the development of new classes of medications has provided the clinician with the tools to decrease intragastric acidity, neutralize or suppress acid production, and enhance the protective and restorative properties of the mucosa.

Sucrose octasulfate stimulates gastric somatostatin release

To explore the mechanisms of the effects of sucralfate on the stomach, we investigated the action of sucrose octasulfate (SOS), a constituent of sucralfate, on the function of canine gastric parietal cells and somatostatin cells and in the isolated perfused intact rat stomach. Somatostatin cells from the canine gastric fundus were isolated by EDTA-collagenase dispersion and counterflow elutriation, and somatostatin-like immunoreactivity (SLI) release in response to SOS was measured by radioimmunoassay. Similar methods were used to isolate gastric parietal cells, in which gastric acid secretion was measured by uptake of a radiolabeled weak base, [14C]aminopyrine. SLI release by the intact rat stomach was examined in an isolated vascularly perfused rat stomach model. SOS, either alone or co-administered with epinephrine or gastrin heptadecapeptide (G17), dose-dependently stimulated SLI release by isolated canine fundic D-cells. At the highest doses, SOS potentiated the effect of epinephrine but not G17. Similarly, SOS potentiated the stimulating effect of dibutyryl cyclic adenosine 3',5'-monophosphate (DBcAMP), but not 12-O-tetradecanoylphorbol 13-acetate (TPA). The effect of SOS on SLI release could be inhibited by octreotide, a somatostatin analogue. SOS did not alter acid secretion by cultured canine parietal cells either in the basal state or when coadministered with acid secretagogues. In isolated perfused rat stomach studies, SOS produced a significant (60% greater than basal) increase in SLI secretion. There was a similar effect when SOS was perfused against a background of isoproterenol. SOS stimulates SLI release from gastric somatostatin cells and from the isolated perfused stomach but has no direct effect on gastric parietal cells. These actions of SOS may mediate in part the apparent ability of sucralfate to enhance gastric mucosal defense.

Hyperaluminaemia in critically ill patients: role of antacid therapy and impaired renal function

A significant rise in serum concentrations of aluminum was demonstrated in 23 patients prophylactically treated with the antacid magaldrate, whereas no increase in serum aluminium was observed in another 26 critically ill patients, in whom the use of antacids was avoided. In parallel, urinary excretion rates of aluminum rose to values close to maximum 72 h after antacid therapy had been started. Hyperaluminaemia was most marked in patients with acute renal failure undergoing continuous haemofiltration, but a significant increment in serum aluminium was also noted in patients with impaired renal function in the predialytic state. In the latter group and in patients with normal renal function there was a significant negative correlation between urinary excretion rates of aluminium and creatinine clearance after 48 h of treatment suggesting an enhancement of gastrointestinal absorption of aluminium in the presence of chronic renal failure. Maximum serum concentrations of aluminium did attain critical values in some patients with acute renal failure, but no overt signs of aluminium toxicity were noted. However, in light of both, possible subtle toxicity and enhanced absorption of aluminium in critically ill patients with renal failure, the prophylactic use of antacids in this setting should be re-evaluated cautiously.

Sucralfate significantly reduces ciprofloxacin concentrations in serum

The effect of sucralfate on the bioavailability of ciprofloxacin was evaluated in eight healthy subjects utilizing a randomized, crossover design. The area under the concentration-time curve from 0 to 12 h was reduced from 8.8 to 1.1 micrograms.h/ml by sucralfate (P less than 0.005). Similarly, the maximum concentration of ciprofloxacin in serum was reduced from 2.0 to 0.2 micrograms/ml (P less than 0.005). We conclude that concurrent ingestion of sucralfate significantly reduces the concentrations in serum produced by a 500-mg dose of ciprofloxacin. On the basis of these findings, ciprofloxacin and sucralfate should not be administered concurrently.