Sucralfate and ranitidine in the treatment of acute duodenal ulcer. Healing and relapse. Ulcer Study Group

The development of clinical practice guidelines for treatment of peptic acid diseases in a VA ambulatory care clinic

The costly treatment of peptic acid diseases at a Veterans Affairs ambulatory care clinic prompted the development of clinical practice guidelines (CPGs) for the disorders. A committee consisting of a clinical pharmacist, the chiefs of ambulatory care and medicine, and a gastroenterologist guided the process. A consensus-style conference format involving medical staff and residents, pharmacists, and other health providers was chosen to develop the CPGs. Before the conference each participant received a list of key issues and literature on practice guidelines, and on peptic acid diseases and their treatment. At the conference the participants were divided into four groups; each group discussed specific key issues using a modified nominal group process. Recommendations from each group were made to the entire conference. Final recommendations were compiled into what was adopted and readily received as the CPGs for the institution.

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.

Pharmacodynamics as a tool to assess the bioequivalence of non-systemically available drugs: size of the sample required

Bioequivalence studies of drugs which are not systematically available must rely on the measure of the pharmacological response. Detection of a difference between two such preparations is often hampered by the need to include an elevated number of subjects. The number of subjects can be reduced whenever: (a) the characteristics of the subjects are well defined, (b) the selection of the baseline target effect is done rigorously, (c) the target effect can be quantified reliably, (d) the effect is measured when less variability is expected, e.g. at steady state, (e) the effect is measured repeatedly, and (f) when possible, the predicted maximal effect (Emax) and the concentration to elicit 50% of Emax are estimated. A simple equation has been derived to estimate the number of subjects needed in these bioequivalence studies.

Clinical efficacy of sucralfate in the treatment of gastric ulcer

We performed a randomized, single-blind study in Japan to investigate the efficacy and safety of two dosage regimens of sucralfate granules, 2 g, twice daily (b.i.d. group, n = 30) and 1 g, 4 times daily (q.i.d. group, n = 27), on ulcer healing in 57 patients with endoscopically proven gastric ulcer. Endoscopy was performed after 4 weeks and, if complete healing was not achieved, again after an additional 4 weeks. Of 57 patients, 11 were excluded from the statistical analysis because of protocol violation (six in b.i.d. group, five in q.i.d. group). Of 46 patients eligible for the analysis of healing rates, four patients in the b.i.d. group (all at 8 weeks) and five patients in the q.i.d. group (two at 4 weeks and three at 8 weeks) were withdrawn due to patients' inconvenience. As the possibility that the withdrawals were due to the treatment failures could not be denied, we used the Kaplan-Meier method and generalized Wilcoxon test/logrank test for the calculation and evaluation of healing rates in this study, respectively. Healing rates at 4 and 8 weeks were 50% and 94% in the b.i.d. group and 35% and 68% in the q.i.d. group. There was no significant difference in healing rates between the groups. No serious adverse effect was observed in either group. These results suggest that the 2 g b.i.d. dose of sucralfate in granule form is at least as effective as the conventional dose of 1 g q.i.d. in the treatment of active gastric ulcers and could lead to better patient compliance.

The effects of sucralfate and luminal stasis on recovery of the chambered rat gastric mucosa from taurocholate-induced damage

We have previously shown, using a gastric chamber model, that both sucralfate and luminal stasis protected the rat gastric mucosa against the development of hemorrhagic erosions produced by subsequent exposure for 10 minutes to acidified (50 mM HCl) 80 mM sodium taurocholate (NaT). The protection afforded by sucralfate was abolished by inhibition of cyclooxygenase activity but restored by sucralfate. In this study we demonstrate that indomethacin pretreatment decreases both the depth (in microns) and magnitude (in pH units) of the juxtamucosal pH gradient, but that sucralfate restores these parameters to levels characteristic of normal mucosae. The cytoprotective effect of sucralfate is thus prostaglandin-independent and, at least in part, a consequence of sucralfate-induced increases in the thickness of the juxtamucosal pH gradient/unstirred layer. We have also examined the ability of sucralfate to prevent the otherwise inevitable development of hemorrhagic erosions when it was applied after the gastric mucosa was exposed to NaT. When 100 mg sucralfate in 50 mM HCl was applied for 10 minutes, without stirring, subsequent to a 10-minute exposure of the mucosa to NaT, the average lesion area was reduced from about 15% to less than 3%. Unlike its cytoprotective property, the ability of sucralfate to accelerate the recovery process after damage was abolished by indomethacin pretreatment. Studies using antimony microelectrodes revealed that indomethacin pretreatment resulted in reductions in both the depth and magnitude of the pH gradient that resulted from plasma efflux from the mucosa after exposure to the acidified bile salt. These studies demonstrate that sucralfate is capable not only of prevention or attenuation of acute damage when administered prior to damaging agents, but is also capable of arresting the sequence of events that produces hemorrhage in the previously inflamed or damaged stomach.

Treatment of duodenal ulcer with sucralfate

Sucralfate attains a healing rate of about 79% for duodenal ulcer in 4 weeks, which is similar to the effects of cimetidine and ranitidine. Whereas cigarette smoking significantly affects duodenal ulcer healing by acid-reducing agents, the healing rates of smokers and non-smokers treated with sucralfate or colloidal bismuth are indistinguishable, suggesting an inherent advantage through the cytoprotective mechanisms of these agents. The 12-month relapse curves for duodenal ulcers initially healed with sucralfate and colloidal bismuth subcitrate closely overlap each other and are significantly lower than the curves for the histamine H2-receptor antagonists. These findings cannot be accounted for by clearance of Helicobacter pylori, on which sucralfate has little effect. Preliminary evidence suggests that the use of acid-reducing agents results in up-regulation of the parietal cells and may help to explain the differences in relapse rates. Sucralfate is superior to placebo and comparable to H2 antagonists in the prevention of duodenal ulcer recurrence.

Why do ulcers heal with sucralfate?

It is unknown why ulcers in general heal. Some clues are worth considering. What is known is (i) that ulcer healing occurs spontaneously, (ii) that ulcers heal more quickly in the duodenum than in the stomach, (iii) that mucosal blood flow at ulcer edge improves with healing, and (iv) that healing can be speeded up by (a) not smoking, (b) removing acid from the stomach, and (c) using non-antisecretory mucosal protective agents such as sucralfate and colloidal bismuth. The difference in healing rates between duodenal and gastric ulcers may be related to ulcer size, duodenal alkalinity due to the secretion of the Brunner's glands, and other uninvestigated factors such as epidermal growth factor and mucosal blood flow. The difference between smokers and non-smokers may be related to inhibition of prostaglandin synthesis and impairment of mucosal blood flow due to smoking and to higher acid secretion in smokers. The success with antisecretory agents indicates that acid inhibits the healing process. The success of sucralfate and bismuth indicates that cytoprotective mechanisms play a role in ulcer healing. The literature also shows that ulcer healing is less affected by smoking in patients treated with sucralfate than in those treated with antisecretory agents, suggesting that cytoprotective mechanisms play a more important part than acid inhibition in counteracting the adverse effects of smoking on healing. Furthermore, ulcer relapse occurs sooner in patients treated with antisecretory agents than in those treated with sucralfate or bismuth, suggesting that withdrawal of antisecretory agents speeds up relapse and/or that cytoprotective mechanisms are associated with longer-lasting remission. It is concluded that sucralfate healing involves cytoprotective mechanisms and that these cannot be ignored in the planning of any anti-ulcer therapy. Despite the understanding of the various site-protective and cytoprotective mechanisms, as discussed in the previous article, it is not clear why ulcers heal with sucralfate. In fact, there is no clear answer to the fundamental question as to why ulcers in general heal with the known therapeutic agents, including H2-receptor antagonists, antacids, proton pump inhibitors, anticholinergics, site-protective agents, and cytoprotective agents. This review examines this question, using sucralfate as a model.

Implications of sucralfate-induced ulcer healing and relapse

A review of the literature indicates that sucralfate attains a healing rate of 79 percent for duodenal ulcer and 75 percent for gastric ulcer in four and eight weeks, respectively, rates not different from those reported for cimetidine and ranitidine. Meta-analyses show that, whereas cigarette smoking significantly affects duodenal ulcer healing by acid-reducing agents, the healing rates of smokers and non-smokers treated with sucralfate are indistinguishable, suggesting an inherent advantage through the underlying mechanisms of the drug. Pooling reports in the literature indicates that the 12-month relapse curves of duodenal ulcers initially healed with sucralfate and colloidal bismuth subcitrate closely overlap each other and are significantly lower than the curves of the histamine (H2)-receptor antagonists under comparison. A review of the ulcer relapse rates following initial healing in the literature shows that patients receiving acid-reducing agents such as antacids, H2-receptor antagonists, and omeprazole have relapses at similar rates. Use of anticholinergics or non-antisecretory agents including carbenoxolone sodium is associated with a longer remission. Preliminary evidence is available to support the concept that the use of acid-reducing agents results in up-regulation, whereas the use of anticholinergics and non-antisecretory agents is associated with down-regulation of the parietal cells. These changes at the molecular level may help to explain the differences in relapse rates following initial healing with various anti-ulcer agents.