Sucralfate

Radiation proctitis: current strategies in management

Radiation proctitis is a known complication following radiation therapy for pelvic malignancy. The majority of cases are treated nonsurgically, and an understanding of the available modalities is crucial in the management of these patients. In this paper, we focus on the current treatments of radiation proctitis.

What are the current possibilities in treating peptic ulcer disease?

There are two major principles of ulcer therapy. Today, the most widely accepted drugs are those which substantially reduce aggressive factors (i.c. acid and pepsin), namely histamine H2-receptor antagonists, antimuscarinics and antacids. Less frequently applied are mucoprotective agents like colloidal bismuth compounds and sucralfate. Prostaglandins both reduce acid secretion substantially and are believed to enhance mucosal resistance. Their anti-ulcer efficacy, however, is solely explicable by their antisecretory activity. Although mucosa-strengthening agents and H2-receptor blockers have nearly identical healing rates, mucosa-strengthening agents have inconvenient dosage regimens (four times or twice daily) and are probably less effective in relieving pain. The same holds true for antacids. Prostaglandins, antimuscarinics and antacids have dose related side effects. In contrast, H2-receptor blockers are characterized by a clear mechanism of action, convenient dosage regimens, good tolerance and a low incidence of side-effects. H2-receptor antagonists are the most effective anti-ulcer drugs presently available.

Characterization of a novel cell damage model induced by acid and pepsin using rat gastric epithelial cells: protective effect of sucralfate

We have established a new model for rat gastric epithelial cell (RGM1) damage caused by both acid and pepsin. Exposure of RGM1 to an acidified medium (pH 3.5-5.0) for 10-50 min decreased cell viability in a time- and pH-dependent manner. Pepsin (0.5-1.0 mg/mL) at pH 4.5 potentiated cell damage in a concentration-dependent manner. Based on these results, two types of cell damage models caused by incubation of cells at pH 4.0 and with pepsin (0.75 mg/mL) at pH 4.5 for 30 min, respectively, were established. The intracellular pH (pHi) gradually decreased with a decrease in medium pH and an increase in exposure time. At pH < or = 4.0, pHi reached approximately pH 6.3. Pepsin at pH 4.5 caused a further reduction in pHi compared with the acidified medium alone. Pepsin pre-incubated with pepstatin did not induce any cell damage. Pretreatment with sucralfate (0.1-3 mg/ mL) for 2 h significantly prevented cell damage caused at both pH 4.0 and with pepsin at pH 4.5 in a concentration-dependent manner. Sucralfate (3 mg/mL) significantly prevented the reduction in pHi at pH 4.0 or with pepsin at pH 4.5. 16,16-Dimethyl prostaglandin E2 (30 micrograms/mL) had no effect on either cell damage or pHi. These cell damage models involving RGM1 are useful for studying the mechanism underlying cell damage and for the screening of cytoprotective drugs.

Utilization of a human intestinal epithelial cell culture system (Caco-2) for evaluating cytoprotective agents

Human intestinal epithelial cells (Caco-2) were cultured as confluent monolayers on polycarbonate membranes in Transwells for investigating their applicability in evaluating the cytoprotective activity of sucralfate. The control experiments established a reproducible chemical method (using 0.5 mM indomethacin in Hanks' balanced salt solution) for inducing damage to the Caco-2 cell monolayers. Damage was determined by measuring changes in transepithelial electrical resistance (TEER). Twenty-day-old Caco-2 cell monolayers were significantly and reproducibly damaged (compared to buffer alone) (P < 0.001) by application of 0.5 mM indomethacin to the apical side for 1 hr. While sucralfate, at a 0.5, 2, or 5 mg/mL concentration in the buffer, was shown not to reverse (treat) the damage caused by indomethacin in this cellular model, it was able to protect (prevent) the cells from indomethacin-induced damage (P < 0.001). We observed that indomethacin-induced damage to the Caco-2 cell monolayers greatly affected the paracellular pathway since the percentage transport of [3H]methoxyinulin was significantly elevated. In contrast, protection of the Caco-2 cells with 5 mg/mL sucralfate in the presence of the damaging agent resulted in transport of the paracellular marker similar to that in the control (HBSS-treated) cell monolayers. This direct cytoprotective effect was thus independent of vascular factors at neutral pH and was observed to be dose dependent (0.5 to 5 mg/mL) when sucralfate was applied to the cells in the presence of the damaging agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of sucralfate and its components on taurocholate-induced damage to rat gastric mucosal cells in tissue culture

The present study evaluated the effect of sucralfate and its components, sucrose octasulfate and aluminum hydroxide, on: (1) damage to rat cultured gastric mucosal cells induced by sodium taurocholate in a neutral environment and in conditions independent of systemic factors, (2) prostaglandin E2 and on 6-keto prostaglandin F1 alpha release by cultured cells, and (3) sulfhydryl content of cultured cells. Cell damage was quantitated by chromium-51 release assay. Prostaglandin E2 and 6-keto prostaglandin F1 alpha were measured by radioimmunoassay. Total sulfhydryl content of cultured cells was determined calorimetrically. Microscopically, sucralfate was found to adhere tightly to epithelial cell surfaces despite frequent washings. Sucralfate 2 mg/ml and 5 mg/ml significantly decreased taurocholate-induced damage, reducing taurocholate-induced specific 51Cr release by 11.8 points (equal to 29% decrease in cell damage, P less than 0.01) and 22.9 points (equal to 56% decrease in cell damage, P less than 0.001), respectively. Sucrose octasulfate and aluminum hydroxide did not exert significant protection against damage induced by sodium taurocholate. The protective effect of sucralfate was not prevented by indomethacin, nor was it counteracted by the sulfhydryl blocker, iodoacetamide. Sucralfate, but not its components, significantly and dose-dependently stimulated prostaglandin E2 (r = 0.94, P less than 0.05) and 6-keto prostaglandin F1 alpha (r = 0.89, P less than 0.05) production by cultured cells. Neither sucralfate nor its components affected sulfhydryl content of cultured cells. In conclusion, sucralfate, but not its components, (1) protects rat gastric mucosal cells against taurocholate-induced damage in conditions independent of systemic factors and in a neutral environment and (2) significantly stimulates prostaglandin production by cultured cells. (3) The protection by sucralfate in vitro does not seem to depend on its stimulatory effect on endogenous prostaglandin synthesis.

The pharmacology of antiulcer drugs

The use of medications for the treatment of gastrointestinal ulcers has evolved to a great extent since the early days of therapy with diet and antacids. Today a number of different agents are available to treat the causative factors of ulcer formation. Currently, antacids, histamine2-receptor antagonists, and sucralfate are considered frontline therapies suitable for most patients. The future also looks promising for newer agents, such as omeprazole and prostaglandin analogs. The purpose of this article is to provide practitioners with an understanding of the achieved more efficiently and effectively.

Efficacy of sucralfate and cimetidine in protection of the human gastric mucosa against alcohol injury

In order to study whether sucralfate or cimetidine may protect human gastric mucosa against alcohol injury, 28 healthy volunteers were pretreated with either: (1) placebo 1 g; (2) cimetidine (Tagamet) 300 mg; or (3) sucralfate (Carafate) 1 g. One hour later, 100 ml of 40 percent ethanol was sprayed directly on the gastric mucosa of the greater curvature during an endoscopic examination. Gastric mucosal changes were assessed by endoscopic appearance (according to grading scale) and by histology. In placebo-pretreated subjects, alcohol produced prominent mucosal damage (endoscopic score, 3.9 +/- 0.3, histologic score, 4.0 +/- 1.1 at 30 minutes). Cimetidine alkalinized gastric pH but did not prevent alcohol-induced damage (endoscopic score, 4.0 +/- 0.6; histologic score, 3.8 +/- 1.1, at 30 minutes). Sucralfate reduced endoscopic and histologic features of alcohol injury (endoscopic score, 1.8 +/- 0.6; histologic score, 1.8 +/- 1.1, at 30 minutes) without affecting gastric luminal pH. Reduction of alcohol-induced injury of the human gastric mucosa by sucralfate but not cimetidine demonstrates that effective protection of the gastric mucosa can be achieved without neutralization or inhibition of gastric acid secretion and points out another clinical application for sucralfate.

Cytoprotective drugs. Focus on essential fatty acids and sucralfate

Cytoprotection has been defined as an ability of prostaglandins to prevent gastric mucosal injury produced by a variety of ulcerogenic and necrotizing agents without inhibition of gastric acid secretion or without neutralizing intragastric acidity. Since the first demonstration of cytoprotection by prostaglandins many other agents have been claimed to be cytoprotective. Essential fatty acids: arachidonic and linoleic, licorice products, sucralfate, antacids and sulfhydryl compounds all possess cytoprotective properties. All of these compounds are able to prevent or reduce gastric mucosal necrosis produced by absolute ethanol, a necrotizing agent which injures mucosa independently of the luminal pH. Gastric mucosal protection by essential fatty acids is mediated by their conversion by the gastric mucosa to protective prostaglandins. Sucralfate and antacids are also cytoprotective compounds which stimulate release of endogenous prostaglandins from the gastric mucosa.

Does sucralfate affect the normal gastric mucosa? Histologic, ultrastructural, and functional assessment in the rat

Although the action of sucralfate on ulcerated mucosa has been demonstrated, its effect on the histology, ultrastructure, and function of normal gastric mucosa is unknown. We investigated the effect of acute administration of sucralfate on the gastric mucosal history, ultrastructure, mucosal potential difference, and luminal release of prostaglandin E2. At 15 min, 1 h, and 3 h after intragastric instillation of sucralfate, whitish incrustations of the drug were firmly adhering to the glandular mucosa. Mucosal histology after sucralfate administration demonstrated the following: disruption and exfoliation of some of the surface epithelial cells, mucosal hyperemia, prominent release of mucus from the surface epithelial cells, and edema of lamina propria and submucosa. These changes were most prominent in the areas where sucralfate was in contact with the mucosal surface. Scanning and transmission electron microscopy confirmed the above changes. Sucralfate produced a drop in gastric mucosal potential difference and a significant increase in luminal release of prostaglandin E2. Sucralfate produces distinct morphologic and functional changes in the normal gastric mucosa, which may account for its preventive and therapeutic efficacy.

Comparison of antacid, sucralfate, cimetidine, and ranitidine in protection of the gastric mucosa against ethanol injury

The abilities of antacid (Mylanta II), sucralfate, cimetidine, and ranitidine to protect the gastric mucosa against ethanol-induced necrosis were compared in a standardized, experimental rat model. Fasted rats received pretreatment with either saline, Mylanta II, 500 mg/kg of sucralfate, 50 mg/kg of cimetidine, or 50 mg/kg of ranitidine. This was followed one hour later by intragastric administration of 2 ml of 100 percent ethanol. Gastric mucosal injury was assessed four hours after administration of ethanol by quantitation of gross mucosal necrosis, assessment of mucosal histology, and determination of intragastric blood and protein concentrations. Pretreatment with Mylanta II or sucralfate significantly reduced ethanol-induced gastric mucosal necrosis. The protective effect of sucralfate was six to 10 times greater than that of Mylanta II. H2-receptor antagonists increased ethanol-induced gastric mucosal necrosis.

Protective effect of sucralfate against alcohol-induced gastric mucosal injury in the rat. Macroscopic, histologic, ultrastructural, and functional time sequence analysis

Histologic or ultrastructural evidence of the ability of sucralfate to protect the gastric mucosa against ethanol injury is lacking. Therefore we analyzed morphologic and functional changes in the mucosa of 120 rats receiving, intragastrically, 2 ml of either sucralfate 500 mg/kg body wt or a control solution and 1 h later 2 ml of 100% ethanol. At 15 min, 1, 4, 6, and 24 h after ethanol instillation, mucosal changes were assessed by macroscopic examination, quantitative histology, scanning electron microscopy, recordings of gastric potential difference, and measurements of volume, pH, and electrolytes in the gastric contents. Between 15 min and 24 h after ethanol instillation, macroscopic necrotic lesions in controls involved greater than 33% of mucosal area and in the sucralfate-treated group less than 4% (p less than 0.001 for each period). In controls, ethanol instillation produced surface epithelial cell disruption and deep (greater than 0.2 mm) mucosal necrosis involving greater than 55% +/- 3% of the mucosal length. In sucralfate-pretreated animals, disruption of the surface epithelium was present at 15 min, 1 h, and 4 h after ethanol instillation, but deep necrotic lesions were virtually absent (0%-2%; p less than 0.001 vs. controls) during the entire study period. The surface epithelium was mostly reestablished by 6 h after ethanol instillation in the sucralfate group but not in the controls. We concluded that sucralfate protects the gastric mucosa against ethanol-induced injury by preventing deep mucosal necrosis and as a consequence the mucosal proliferative zone cells rapidly restitute mucosal integrity.

Effect of sucralfate on the bioavailability of indenolol

Effect of concurrent administration of sucralfate on the bioavailability of indenolol in rats has been investigated. Albino rats were administered with lg/kg body weight of sucralfate just before the oral administration of indenolol solution (10 mg/kg), blood samples were collected at 0,15,30,45,60,120,240 and 360 minutes after the administration of drugs. Indenolol concentration was determined spectrofluorometrically, 2,4, and 6-hour Area Under the Curve (AUC) was calculated. The peak indenolol blood concentration was observed at 45th minute of drug administration. The level in rats treated with indenolol alone (2.46 +/- 0.07 microgram/ml) and indenolol along with sucralfate (1.21 +/- 0.06 microgram/ml) suggested more than a 50% decrease. There were 36.4%, 27.2% and 20.4% decrease in 2-hour AUC, 4-hour AUC and 6-hour AUC respectively. The data suggest that sucralfate significantly decreased the absorption of indenolol, especially in the early phase after administration and clinically significant interaction may occur due to concurrent administration of indenolol with sucralfate.