Bismuth subsalicylate in the treatment of H2 blocker resistant duodenal ulcers: role of Helicobacter pylori

The versatile biomedical applications of bismuth-based nanoparticles and composites: therapeutic, diagnostic, biosensing, and regenerative properties

Studies of nanosized forms of bismuth (Bi)-containing materials have recently expanded from optical, chemical, electronic, and engineering fields towards biomedicine, as a result of their safety, cost-effective fabrication processes, large surface area, high stability, and high versatility in terms of shape, size, and porosity. Bi, as a nontoxic and inexpensive diamagnetic heavy metal, has been used for the fabrication of various nanoparticles (NPs) with unique structural, physicochemical, and compositional features to combine various properties, such as a favourably high X-ray attenuation coefficient and near-infrared (NIR) absorbance, excellent light-to-heat conversion efficiency, and a long circulation half-life. These features have rendered bismuth-containing nanoparticles (BiNPs) with desirable performance for combined cancer therapy, photothermal and radiation therapy (RT), multimodal imaging, theranostics, drug delivery, biosensing, and tissue engineering. Bismuth oxyhalides (BiO_x, where X is Cl, Br or I) and bismuth chalcogenides, including bismuth oxide, bismuth sulfide, bismuth selenide, and bismuth telluride, have been heavily investigated for therapeutic purposes. The pharmacokinetics of these BiNPs can be easily improved via the facile modification of their surfaces with biocompatible polymers and proteins, resulting in enhanced colloidal stability, extended blood circulation, and reduced toxicity. Desirable antibacterial effects, bone regeneration potential, and tumor growth suppression under NIR laser radiation are the main biomedical research areas involving BiNPs that have opened up a new paradigm for their future clinical translation. This review emphasizes the synthesis and state-of-the-art progress related to the biomedical applications of BiNPs with different structures, sizes, and compositions. Furthermore, a comprehensive discussion focusing on challenges and future opportunities is presented.

Does eradication of Helicobacter pylori alone heal duodenal ulcers?

BACKGROUND

Eradication of Helicobacter pylori infection prevents duodenal ulcer (DU) relapse, but it remains uncertain whether eradication of H. pylori alone heals duodenal ulceration.

AIM

To test the hypothesis that eradication of H. pylori infection is accompanied by healing of duodenal ulcer.

METHODS

A total of 115 consecutive patients with endoscopically confirmed H. pylori-infected duodenal ulcer were randomly assigned to one of two groups. Group BTC patients received a 1-week course of colloidal bismuth subcitrate 220 mg b.d., tinidazole 500 mg b.d., clarithromycin 250 mg b.d. Group OBTC patients received omeprazole 20 mg daily for 4 weeks with the BTC regimen during the first week. Endoscopy with antral biopsies and 13C-urea breath test (UBT) were performed before and 4 weeks after completion of the 7-day triple or quadruple therapy.

RESULTS

Eight patients dropped out (four in BTC and four in OBTC). Duodenal ulcer healing rates on an intention-to-treat basis in BTC and OBTC were 86% (95% CI: 77-95%) and 90% (95% CI: 82-98%), respectively. The eradication rates of H. pylori on an intention-to-treat basis in BTC and OBTC were 88% (95% CI: 79-96%) and 91% (95% CI: 84-99%), respectively. There were no statistically significant differences in ulcer healing rates and eradication rates between these two groups (P > 0.05). Epigastric pain resolved more rapidly in patients assigned to OBTC compared with those assigned to BTC. Both of the two regimens were well tolerated with only minor side-effects (3% of the 115 patients) and the compliance was good.

CONCLUSIONS

BTC is a very effective H. pylori eradication regimen. Almost all duodenal ulcers heal spontaneously after cure of H. pylori infection using a 1-week low-dose bismuth-based triple therapy. Treating duodenal ulcer with simultaneous administration of omeprazole achieves ulcer pain relief more rapidly.

Cinnamon extracts' inhibitory effect on Helicobacter pylori

Ethanol and methylene chloride extracts of cinnamon were compared for their effect on Helicobacter pylori growth and urease activity. Methylene chloride extract was found to inhibit growth of H. pylori, while ethanol extract counteracted its urease activity. Cinnamon extract (from methylene chloride) inhibited H. pylori at concentration range of common antibiotics. Complete inhibition in vitro was achieved by 50 microg/ml in solid medium (egg yolk emulsion agar) and by 15 microg/ml in liquid medium (supplemented brain heart infusion broth). The cinnamon extracts were more inhibitory on free urease than on whole cell urease.

Effects of ranitidine bismuth citrate on Helicobacter pylori motility, morphology and survival

AIM

The effects of the anti-ulcer agents ranitidine bismuth citrate (RBC), ranitidine hydrochloride (R) and colloidal bismuth citrate (BC), on Helicobacter pylori motility, morphology and survival were examined to determine whether the clinical effectiveness of RBC might be linked to a specific action that inhibits bacterial motility.

METHODS

H. pylori from patients with duodenal ulcer or non-ulcer dyspepsia were exposed to RBC and BC at bismuth concentrations ranging from 12.5 to 50 microg/mL, and R at ranitidine concentrations ranging from 12.5 to 50 microg/mL for a brief period (< 15 min), 6 h and 24 h. Bacterial motility was assessed with a Hobson BacTracker, bacterial morphology by transmission electron microscopy, and growth inhibition by counting colony-forming units.

RESULTS

H. pylori motility was diminished with RBC and BC but not R. However, the effect of RBC was markedly greater than that of BC at each bismuth concentration and time of exposure tested: (i) brief exposure to RBC/bismuth 50 microg/mL but not to BC, resulted in a significant loss of motility without loss of viability or change in cell morphology, and (ii) bacteria were immobilized, and lost viability after exposure to RBC/bismuth 50 microg/mL for 24 h but not to BC. Morphological destruction caused by RBC differed from that by BC: after 24 h exposure to the highest concentration tested, cell fragmentation and flagella detachment occurred more frequently with BC than RBC, but the latter produced greater disruption of intracellular structures.

CONCLUSIONS

RBC suppresses growth of H. pylori, and has a specific inhibitory effect on the bacterial motor mechanism. These pharmacological actions are likely to contribute to the clinical effectiveness of the agent.

Discontinuation rates of Helicobacter pylori treatment regimens: a meta-analysis

We conducted a meta-analysis to determine what factors in treatment regimens for Helicobacter pylori are associated with increased discontinuation rates. Studies were selected from the 1990-1996 MEDLINE data base, and references in published articles and reviews were obtained. Each article was uniformally abstracted for factors that could potentially affect dropout rates. Drug regimens with high numbers of doses per day had highest dropout rates (p=0.0001). The total dropout rate was lowest for regimens containing a proton pump inhibitor (OR = 0.75, CI 0.57, 0.98). The rate was high in regimens containing a bismuth compound due to side effects (OR = 2.79, CI 1.78, 4.36). The main finding was that drug regimens for eradication of H. pylori that have a high number of doses per day result in higher discontinuation rates than regimens with fewer doses per day.

Antimicrobial therapies for Helicobacter pylori infection in gnotobiotic piglets

Gnotobiotic piglets infected with Helicobacter pylori were treated with various antimicrobials as monotherapy and dual therapy, and the results were compared to those for piglets treated with a triple-therapy regimen (bismuth subsalicyclate at 5.7 mg/kg of body weight, metronidazole at 4.4 mg/kg, and amoxicillin at 6.8 mg/kg four times a day [QID]). Clearance of infection was assessed after 7 days of treatment, and eradication was assessed following 7 days of treatment and a 14-day posttreatment observation interval. Monotherapy with amoxicillin, clarithromycin, and ciprofloxacin cleared and eradicated the organism from porcine stomachs; monotherapy with metronidazole cleared the infection and eradicated it from some piglets. Metronidazole-resistant microbes were recovered from treated piglets which cleared but did not eradicate the infection. Monotherapy with bismuth subsalicylate, erythromycin, nitrofurantoin, and tetracycline in the dosage range of 5.0 to 7.1 mg/kg QID was less than 100% effective in clearance and eradication, in that these drugs cleared and/or eradicated the infection from some of the piglets but did not eradicate the infection from all of the piglets. Monotherapy with an H-2 receptor antagonist (ranitidine) or a proton pump inhibitor (omeprazole) was ineffective at either clearance or eradication. In vivo dose titrations with several effective monotherapies were performed to determine the lowest effective in vivo dose of drug. In piglets, eradication was associated with a statistically significant decline in serum H. pylori-specific immunoglobulin M (IgM) antibodies; the titers of both IgA and IgG also declined, but the values were not statistically significant. For many antimicrobials, piglets are more sensitive indicators of clearance and eradication than humans. These data establish the H. pylori-infected gnotobiotic piglet as a useful model for the identification of novel antimicrobials for the treatment of this disease and for drug assessment during preclinical evaluations.

Prospective, randomized, investigator-blind trial of Helicobacter pylori infection treatment in patients with refractory duodenal ulcers. Healing and long-term relapse rates

In this study, 26 patients with duodenal ulcers refractory to treatment with H2-receptor antagonists for 8-12 weeks were randomly assigned to eight weeks of treatment with colloidal bismuth subcitrate (120 mg four times a day) alone (N = 12) or in combination with tetracycline hydrochloride (500 mg four times a day, days 0-14) and metronidazole (500 mg three times a day, days 15-28). Symptoms were scored and endoscopy, histology, and CLO tests were performed before, on completion of treatment, and 3, 6, 12, and 18 months after treatment. Treatment was considered successful when Helicobacter pylori was not detected by CLO tests and Warthin-Starry stains on gastric biopsies taken from antrum, body, and fundus. On triple therapy, ulcers healed in 12/14 patients (85.71%) and 10/14 (71.42%) patients became Helicobacter pylori-negative. On bismuth, only one patient became Helicobacter pylori-negative (8.33%, P < 0.0001), but ulcers healed in 8/12 patients (67%, P = NS). Six patients on bismuth, whose ulcers remained unhealed or relapsed early after healing, were offered triple therapy, which resulted in ulcer healing in three and Helicobacter pylori clearance in two patients. At 18 months, none of the Helicobacter pylori-negative patients had ulcer relapse. On the contrary, ulcers relapsed in all but one patient, who remained Helicobacter pylori-positive. Smoking and drinking did not influence the therapeutic outcome. The data confirm previous reports that many duodenal ulcers are infectious and therefore curable.

Short and long term outcome of Helicobacter pylori positive resistant duodenal ulcers treated with colloidal bismuth subcitrate plus antibiotics or sucralfate alone

Thirty two patients with Helicobacter pylori positive duodenal ulcers resistant to treatment were randomly assigned to 4 weeks' treatment with sucralphate 4 g/day or colloidal bismuth subcitrate 480 mg/day plus amoxycillin from days 1 to 7 and tinidazole from days 8 to 14. After 4 weeks, patients with unhealed ulcers were crossed over to the other form of treatment for a further 4 week period. Patients with healed ulcers were followed up for 1 year without maintenance therapy with clinical and endoscopic investigations 3, 6, and 12 months after healing. Complete healing rates at 4 weeks were 88% (15 of 17) in the colloidal bismuth subcitrate plus antibiotics group and 40% (six of 15) in the sucralphate group (p < 0.05). After cross over, overall healing rates were 88% (22 of 25) and 47% (eight of 17), respectively (p < 0.05). H pylori eradication occurred in 83% of patients treated with the triple therapy. Cumulative relapse rates at 12 months were 12% (two of 17) in patients in whom H pylori had been eradicated and 100% (10 of 10) in those with persistent infection after short term therapy (p < 0.05). These results show that a colloidal bismuth subcitrate plus antibiotics regimen is highly effective in the short term treatment of resistant duodenal ulcers and that H pylori eradication can change the natural tendency to early recurrence of these ulcers.

Refractory peptic lesions. Therapeutic strategies for ulcers and reflux esophagitis that resist standard regimens

In some patients, peptic lesions fail to heal after 2 to 3 months of standard histamine2 (H2) receptor antagonist or sucralfate (Carafate) therapy. Noncompliance with prescribed treatment, cigarette smoking, gastric acid hypersecretory states (including Zollinger-Ellison syndrome), Helicobacter pylori infection, the use of nonsteroidal anti-inflammatory drugs, abdominal radiation therapy, and malignant tumors are all causes of refractory disease. Treatment options include high-dose H2 receptor antagonist therapy or switching to a more potent drug or one with a different mechanism of action. Occasionally, drug combinations (eg, H2 receptor antagonist plus misoprostol [Cytotec] for gastric ulcers or H2 receptor antagonist plus metoclopramide [Octamide, Reglan] for reflux disease) are effective. Triple-drug therapy for H pylori infection with refractory duodenal ulcers may allow healing and dramatically decrease recurrence rates. When surgery is required, vagotomy and antrectomy is probably the procedure of choice in patients with peptic ulcer disease that is refractory to medical management. Nissen fundoplication is effective in patients with reflux esophagitis who have adequate esophageal motility.

Effect of Helicobacter pylori infection on 24 hour intragastric acidity in patients with gastritis and duodenal ulcer

Helicobacter pylori status, gastric histology, and 24 hour acidity were studied in 35 gastritis patients, 21 duodenal ulcer patients, and 14 subjects with normal gastric mucosa. H pylori was identified in 21 of 35 patients with chronic active gastritis and in 19 of 21 duodenal ulcer patients, but in none of those with normal gastric mucosa. Mean scores of activity of gastritis were similar in H pylori positive gastritis and duodenal ulcer patients, but were significantly lower in H pylori negative gastritis patients (2.1 (0.8) and 2.3 (0.9) v 1.4 (0.7); p < 0.01, respectively). Median 24 hour hydrogen ion activity (interquartile range) was 21 (8.9-38.0) mmol/l in normal subjects and 23 (11.2-49.0) mmol/l, 19 (7.1-33.1) mmol/l, 44 (25.1-63.1) mmol/l, and 36 (31.6-39.8) mmol/l respectively in gastritis and duodenal ulcer patients with and without H pylori infection. During all predefined time periods, intragastric acidity was significantly higher in patients with H pylori positive duodenal ulcers compared with gastritis patients and normal subjects. However, there was no significant difference in intragastric acidity between the H pylori positive and negative gastritis patients. These results suggest that most of the subjects with chronic H pylori infection have normal gastric acidity.