Impact of acid secretion, gastritis, and mucus thickness on gastric transfer of antibiotics in rats

An eco-friendly multi-analyte high-performance thin layer chromatographic densitometric determination of amoxicillin, metronidazole, and famotidine in their ternary mixtures and simulated gastric juice: A promising protocol for eradicating Helicobacter pylori

Gastrointestinal tract disorders constitute a heavy burden to healthcare providers. To eradicate Helicobacter pylori infection, different triple therapy protocols have been proposed. Among which are combinations of proton pump inhibitors (e.g., omeprazole), histamine-2 receptor antagonists (e.g., famotidine), along with antibiotics (e.g., amoxicillin). In this work, a sensitive and accurate high-performance thin-layer chromatographic method was developed for the simultaneous determination of amoxicillin, metronidazole, and famotidine in bulk powder and laboratory-prepared combined-tablet mixtures. Complete separation of the cited compounds was achieved using pre-coated silica gel plates with a mixture of methanol:chloroform:toluene:water:glacial acetic acid (5:2:1.5:0.5:0.1 v/v/v/v/v) as the mobile phase. The method was fully validated as per the international conference of harmonization guidelines. Good linearity, a correlation coefficient of 0.9991, was obtained in the concentration ranges 0.1-1.6 μg/band (amoxicillin), 0.1-0.9 μg/band (metronidazole), and 0.1-0.9 μg/band (famotidine). Since the method allowed the determination of the three compounds in combined tablets with a high degree of selectivity, accuracy, precision, with cost-effectiveness, it could be used for regular quality control. Moreover, the applicability of the proposed method was extended to the determination of the ternary mixture in simulated gastric juice. Method greenness was assessed using different green metrics.

The Spectrum of Helicobacter-Mediated Diseases

Helicobacter pylori is the leading cause of peptic ulcer disease. The infection has been implicated in more than 75% of duodenal ulcer cases and 17% of gastric ulcer cases. H. pylori has been classified as a human carcinogen, since it is the main cause of distal gastric adenocarcinoma and B cell mucosa-associated lymphoid tissue lymphoma. Evidence also links H. pylori with extragastric conditions including iron deficiency anemia, idiopathic thrombocytopenic purpura, and vitamin B₁₂ deficiency. Studies indicate that H. pylori may be protective against other conditions of the gastrointestinal tract (e.g., reflux esophagitis and related pathologies) and elsewhere in the body (e.g., asthma). The infection is asymptomatic in the vast majority of cases; more serious outcomes occur in only 10-15% of infected individuals. Despite extensive research over the past 3 decades, there is no effective vaccine, and the circumstances leading to disease development remain unclear. In addition, there is now a growing prevalence of antimicrobial resistance in H. pylori. This review discusses these important issues.

In Vitro Activity of Sertraline, an Antidepressant, Against Antibiotic-Susceptible and Antibiotic-Resistant Helicobacter pylori Strains

Antibiotic resistance of Helicobacter pylori, a spiral bacterium associated with gastric diseases, is a topic that has been intensively discussed in last decades. Recent discoveries indicate promising antimicrobial and antibiotic-potentiating properties of sertraline (SER), an antidepressant substance. The aim of the study, therefore, was to determine the antibacterial activity of SER in relation to antibiotic-sensitive and antibiotic-resistant H. pylori strains. The antimicrobial tests were performed using a diffusion-disk method, microdilution method, and time-killing assay. The interaction between SER and antibiotics (amoxicillin, clarithromycin, tetracycline, and metronidazole) was determined by using a checkerboard method. In addition, the study was expanded to include observations by light, fluorescence, and scanning electron microscopy. The growth inhibition zones were in the range of 19–37 mm for discs impregnated with 2 mg of SER. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) counted for 2–8 µg/mL and 4–8 µg/mL, respectively. The time-killing assay showed the time-dependent and concentration-dependent bactericidal activity of SER. Bacteria exposed to MBCs (but not sub-MICs and MICs ≠ MBCs) underwent morphological transformation into coccoid forms. This mechanism, however, was not protective because these cells after a 24-h incubation had a several-fold reduced green/red fluorescence ratio compared to the control. Using the checkerboard assay, a synergistic/additive interaction of SER with all four antibiotics tested was demonstrated. These results indicate that SER may be a promising anti-H. pylori compound.

N-acetylcysteine as an adjuvant therapy for Helicobacter pylori eradication

BACKGROUND

Helicobacter pylori (H pylori) is one of the most common pathogens to establish and cause infection in human beings, affecting about 50% of the world's population. Prevalence may be as high as 83% in Latin American countries and as low as 17% in North America. Approximately 20% of infected people will manifest disease; people at high risk include those who live in low- and middle-income countries with poor sanitary conditions, since the mechanism of transmission seems to be oral-oral or faecal-oral (mostly during infancy). There are several antibiotic regimens to treat the infection, but antibiotic resistance is growing around the world. New adjuvant drugs - such as probiotics, statins, curcumin, and N-acetylcysteine (NAC) - are being tested to enhance eradication rates.N-acetylcysteine can destabilise the biofilm structure; it also has synergic action with antibiotics, and bactericidal effects. In addition, NAC has antioxidant properties, and has a primary mucolytic effect by reducing the thickness of the gastric mucus layer, both of which may exert beneficial adjuvant effects on H pylori eradication.

OBJECTIVES

To assess the efficacy and safety of N-acetylcysteine as an adjuvant therapy to antibiotics for Helicobacter pylori eradication.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1966 to April 2018), Embase (1988 to April 2018), CINAHL (1982 to April 2018), LILACS (1982 to April 2018), grey literature databases and trials registries. We handsearched the reference lists of relevant studies. We screened 726 articles and assessed 18 for eligibility.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of any antibiotic regimen plus NAC, in adults infected with H pylori. To be included, trials had to use a control consisting of the same antibiotic regimen with or without placebo. Outcomes of interest were eradication rates, and gastrointestinal, toxic, and allergic adverse events. Reporting of the primary outcomes listed here was not an inclusion criterion for the review.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed and extracted data and completed the 'Risk of bias' assessments. A third review author independently confirmed the 'Risk of bias' assessments. We used Review Manager 5 software for data analysis. We contacted study authors if there was missing information.

MAIN RESULTS

We included eight RCTs (with a total of 559 participants) in this review. The studies recruited outpatients aged between 17 and 76 years who were referred to endoscopy centres in several different countries. The certainty of evidence was reduced for most outcomes due to the poor methodological quality of included studies; issues mainly related to the generation of allocation sequence, allocation concealment, and blinding (this last domain related specifically to adverse outcomes).We are uncertain whether the addition of NAC to antibiotics improves H pylori eradication rates, compared with the addition of placebo or no NAC (38.8% versus 49.1%, risk ratio (RR) 0.74, 95% confidence interval (CI) 0.51 to 1.08; participants = 559; studies = eight; very low-certainty evidence). A post-hoc sensitivity analysis, in which we removed studies that tested antibiotic regimens no longer recommended in clinical practice, showed that the addition of NAC may improve eradication rates compared to control (27.2% versus 37.6%, RR 0.71, 95% CI 0.53 to 0.94; participants = 397; published studies = five).We are uncertain whether NAC is associated with a higher risk of gastrointestinal adverse events compared to control (23.9% versus 18.9%, RR 1.25, 95% CI 0.85 to 1.85; participants = 336; studies = five; very low-certaintyevidence), or allergic adverse events (2% versus 0%, RR 2.98, 95% CI 0.32 to 27.74; participants = 336; studies = five; very low-certainty evidence). There were no reports of toxic adverse events amongst included studies.

AUTHORS' CONCLUSIONS

We are uncertain whether the addition of NAC to antibiotics improves H pylori eradication rates compared with the addition of placebo or no NAC. Due to the clinical, statistical and methodological heterogeneity found in included studies, and the uncertainty observed when analysing therapy subgroups, any possible beneficial effect of NAC should be regarded cautiously.We are uncertain whether NAC is associated with a higher risk of gastrointestinal or allergic adverse events compared with placebo or no NAC. There were no reports of toxic adverse events amongst the included studies.Further large, well-designed, randomised clinical studies should be conducted, with good reporting standards and appropriate collection of efficacy and safety outcomes, especially for current recommended antibiotic regimens.

Additive Effect of Pronase on the Eradication Rate of First-Line Therapy for Helicobacter pylori Infection

Background/Aims

Helicobacter pylori colonizes on the apical surface of gastric surface mucosal cells and the surface mucous gel layer. Pronase is a premedication enzyme for endoscopy that can disrupt the gastric mucus layer. We evaluated the additive effects of pronase combined with standard triple therapy for H. pylori eradication.

Methods

This prospective, single-blinded, randomized, controlled study was conducted between June and October 2012. A total of 116 patients with H. pylori infection were enrolled in the study (n=112 patients, excluding four patients who failed to meet the inclusion criteria) and were assigned to receive either the standard triple therapy, which consists of a proton pump inhibitor with amoxicillin and clarithromycin twice a day for 7 days (PAC), or pronase (20,000 tyrosine units) combined with the standard triple therapy twice a day for 7 days (PACE).

Results

In the intention-to-treat analysis, the eradication rates of PAC versus PACE were 76.4% versus 56.1% (p=0.029). In the per-protocol analysis, the eradication rates were 87.5% versus 68.1% (p=0.027). There were no significant differences concerning adverse reactions between the two groups.

Conclusions

According to the interim analysis of the trial, pronase does not have an additive effect on the eradication of H. pylori infection (ClinicalTrial.gov: NCT01645761).

An Additive Effect of Oral N-Acetyl Cysteine on Eradication of Helicobacter pylori

Background. Helicobacter pylori is highly adapted to the gastric environment where it lives within or beneath the gastric mucous layer. The aim of this study was to evaluate whether the addition of N-acetyl cysteine to the treatment regimen of H. pylori infection would affect eradication rates of the disease. Methods. A total of 79 H. pylori positive patients were randomized to two therapeutic groups. Both groups received a 14-day course of three-drug regimen including amoxicillin/clarithromycin/omeprazole. Experimental group (38 subjects) received NAC, and control group (41 subjects) received placebo, besides three-drug regimen. H. pylori eradication was evaluated by urea breath test at least 4 weeks after the cessation of therapy. Results. The rate of H. pylori eradication was 72.9% and 60.9% in experimental and control groups, respectively (P = 0.005). By logistic regression modeling, female gender (OR 3.68, 95% CI: 1.06–5.79; P = 0.040) and treatment including NAC (OR 1.88, 95% CI: 0.68–3.15; P = 0.021) were independent factors associated with H. pylori eradication. Conclusion. The results of the present study show that NAC has an additive effect on the eradication rates of H. pylori obtained with three-drug regimen and appears to be a promising means of eradicating H. pylori infection.

Effect of rabeprazole on the transport and distribution of levofloxacin in rat stomachs

The aim of this study was to determine the transport and distribution characteristics of levofloxacin in the rat stomach and investigate the effects of combination treatment with rabeprazole. A total of 160 Wistar rats were randomly divided into four treatment groups: 50 mg/kg levofloxacin, 100 mg/kg levofloxacin, 50 mg/kg levofloxacin + rabeprazole and 100 mg/kg levofloxacin + rabeprazole. For two hours after intravenous administration, serum, gastric juice and stomach mucosa samples were collected at 15-min intervals, and the levofloxacin concentrations in all the samples were measured to determine the transport and distribution characteristics of levofloxacin in the rat stomach. In the 50 mg/kg levofloxacin and the 100 mg/kg levofloxacin groups, the drug concentration in the gastric juice gradually exceeded the serum concentration within 45–60 min of administration (P<0.05) and the drug concentrations in the gastric body and antrum were higher than those in the serum and the forestomach (P<0.05). At 15–30 min after administration, the drug concentrations in the gastric juice in the 50 mg/kg levofloxacin + rabeprazole and the 100 mg/kg levofloxacin + rabeprazole groups gradually exceeded the serum concentration (P<0.05). However, the levofloxacin concentration in the gastric body and in the antrum did not significantly differ between the two groups (P>0.05). The levofloxacin concentrations in each stomach region in the groups also treated with rabeprazole were higher than those treated with levofloxacin alone, but the differences were not significant. The levofloxacin transport fractions in the stomach in the 50 mg/kg levofloxacin, 100 mg/kg levofloxacin, 50 mg/kg levofloxacin + rabeprazole and 100 mg/kg levofloxacin + rabeprazole groups were 2.36, 2.52, 2.42 and 2.55, respectively, and no significant difference was identified. Levofloxacin may be actively transported in the rat stomach. The levofloxacin concentration in the gastric antrum exceeded that in the forestomach, and the local concentration increased with increasing dosage. Combining a proton pump inhibitor with levofloxacin has little effect on the concentration and distribution of levofloxacin in the stomach within 2 h.

Efficacy and pharmacological mechanism of pronase-enhanced low-dose antibiotics for Helicobacter pylori eradication

This study examined the efficacy and pharmacological mechanism of pronase-assisted low-dose antibiotics for eradication of Helicobacter pylori. Mongolian gerbils infected with H. pylori received 7-day treatment (omeprazole, different concentrations of pronase, amoxicillin, and clarithromycin), and the efficacy was assessed using the eradication rate and the colonization of H. pylori. In Mongolian gerbils orally administered pronase, the thickness of the gastric mucous layer (GML) was examined using immunohistochemical and alcian blue staining, and the concentrations of amoxicillin in gastric tissue and serum were detected using high-performance liquid chromatography (HPLC). The eradication rates were 80.0% (12/15) in the high-pronase quadruple group (HPQG) and 86.7% (13/15) in the high-antibiotic group (HAG) (P = 1.000). The antibiotic dose in the HPQG was only 1/20 that in the HAG. Thirty minutes after oral treatment with pronase, the sticky protein of the GML was hydrolyzed, and the GML became thinner. Higher amoxicillin concentrations in both the gastric tissue and serum were observed in the pronase group than in the Am10 group. The concentration of amoxicillin in the Am10-plus-Pr108 group in gastric tissue was 3.8 times higher than in the Am10 group in 5 min. Together, these data suggest that pronase significantly reduced the dose of antibiotics used in H. pylori eradication. The pharmacological mechanism is likely pronase removal of the mucus layer, promoting chemical factor (i.e., gastric acid and pepsinogen) distribution and increasing the antibiotic concentrations in the deep GML, which acted on H. pylori collectively. Thus, pronase may enhance the level of antibiotics for eradication of H. pylori in the clinic.

454-pyrosequencing analysis of normal gastric mucosal microbiota

AIM: To characterize the normal gastric microbiota.

METHODS: Genomic DNA was extracted from antral biopsies obtained from two patients who had histologically normal gastric mucosa. The 16S rRNA gene was amplified using PCR. The barcoded 454-pyrosequencing method was used to analyze the amplified products. To investigate the community structure, diversity and abundance of gastric microbiota, sequence analysis was performed using bioinformatic methods including OTU hierarchical clustering and alpha diversity analysis.

RESULTS: High-throughout sequencing of the gastric microbiota from patients A and B obtained 20565 and 17487 sequences, respectively. The coverage was greater than 0.98. Gastric microbiota was composed of 638 and 667 OTUs, respectively. Alpha diversity analysis revealed that Chao and Shannon indices of gastric microbiota were slightly lower than those of fecal microbiota. For patient A, the gastric microbiota was composed of 58 bacterial genera belonging to 14 phyla. Proteobacteria, Actinomycetes, Firmicutes and Bacteroides were dominant in the gastric microbiota from patient A. The gastric microbiota from patient B had a similar bacterial composition, consisting of 64 bacterial genera belonging to 19 phyla. Serratia was the predominant genus in both patients.

CONCLUSION: Normal gastric microbiota shows a high diversity. Proteobacteria is the most abundant phylum, while Serratia is the predominant genus.

Treatment for H. pylori infection: new challenges with antimicrobial resistance

The treatment of Helicobacter pylori infection is in a state of flux as traditional therapies fail and new therapies do not achieve the 90% eradication rates desired by clinicians. Triple therapy, which has been the mainstay of treatment in many countries over the last decade, now has suboptimal results in many parts of the world. A number of new treatments have been described with variable success in different parts of the world. In this article, the fundamentals of treatment for H. pylori treatment are reviewed and new treatment algorithms are proposed for regions of the world where triple therapy is failing. Sequential therapy and quadruple therapy (either bismuth-based or non-bismuth-based) are the best current options to replace initial treatment with triple therapy. When initial treatment fails, salvage treatments using rifabutin and levofloxacin are the best options. With knowledge of local resistance patterns and with meticulous confirmation of eradication with retreatment, most H. pylori infections can be successfully eradicated.

Transfer and distribution of amoxicillin in the rat gastric mucosa and gastric juice and the effects of rabeprazole

AIM

To investigate the distribution of amoxicillin in the gastric juice and gastric mucosa of rats and to investigate the effects of proton pump inhibitor rabeprazole on amoxicillin concentrations in various compartments.

METHODS

One hundred and sixty anesthetized rats were divided into five groups, and given intravenously different doses of amoxicillin or amoxicillin and rabeprazole. The pH value and volume of gastric juice was aspirated were measured and separated gastric mucosa was homogenized. The concentrations of amoxicillin in the plasma, gastric juice and gastric mucosa were measured by high performance liquid chromatography (HPLC).

RESULTS

The maximum concentrations of amoxicillin in gastric juice and gastric mucosa were significantly lower than those in plasma (P<0.001). Concentrations in the glandular stomach mucosa were higher than those in the forestomach mucosa. Rabeprazole did not significantly change the pharmacokinetic parameters of amoxicillin in the plasma and did not alter gastric antibiotic clearance or the gastric transfer fraction of amoxicillin in gastric juice. However, rabeprazole did increase the amoxicillin concentration and pH value in gastric juice and reduced the volume of the gastric juice.

CONCLUSION

Amoxicillin could penetrate the gastric mucosa and achieve therapeutic concentrations at the target site after transfer from the blood to the stomach. Rabeprazole increased the amoxicillin concentration in gastric juice by decreasing the gastric juice volume but did not affect its concentration in blood or gastric mucosa.

H. pylori treatment: new wine in old bottles?

Treatment of Helicobacter pylori infection has become a problem in many clinical settings. Eradication rates are at the lowest levels seen in the past decade and are likely to fall further as antimicrobial resistance becomes more prevalent worldwide. Culture of H. pylori and antimicrobial sensitivity testing is still not generally available; therefore treatment strategies that are selected based on information that is specific to the individual patient are often not possible. Current strategies for treatment in most Western countries consist of initial therapy with a combination of a proton pump inhibitor therapy with amoxicillin and clarithromycin, with quadruple therapy reserved for failures. Sequential therapy is an attractive new alternative for initial treatment and may offer an alternative to conventional therapies. The choice of initial therapy is in a state of flux and this article will discuss alternative treatment strategies that clinicians may use in this difficult environment.

Eradication therapy for Helicobacter pylori

Eradication therapy for Helicobacter pylori is recommended in a number of clinical conditions. In this article, we discuss the epidemiology and cellular mechanisms that result in antimicrobial resistance, the results of current eradication therapies, and new approaches to the management of Helicobacter pylori infection.

Treatment and dosing of Helicobacter pylori infection: when pharmacology meets clinic

Helicobacter pylori infection is a major cause of diseases located in the upper gastrointestinal tract. Successful eradication of the bacteria may improve H. pylori-related symptomatic complaints in functional dyspepsia, cure peptic ulcer disease and prevent gastric cancer. As vaccines are not available, the search for the optimal drug regimen has dominated the last decade. Today, most countries prefer a 7- to 10-day regimen containing a proton pump inhibitor, clarithromycin and amoxicillin as first-line treatment. An alternative (or second-line) treatment contains a proton pump inhibitor, bismuth, tetracycline and metronidazole. This review also highlights the impact of new drugs, new drug combinations, and their optimal dosing required to maximise clinical outcome.

Helicobacter pylori treatment: a practical approach

The treatment of Helicobacter pylori infection has become complicated by the lack of new treatment regimens and the emergence of drug resistant strains of H. pylori. Metronidazole and clarithromycin resistance are common in developed countries. Eradication rates have been falling in trials and in clinical practice around the world. A practical approach to the treatment of patients with H. pylori infection and those who fail initial eradication therapy is discussed.

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Effect of N-acetyl cysteine on Helicobacter pylori

BACKGROUND

Use of mucolytic agents that result in reduced mucous viscosity of the gastric mucous has been suggested to have an additive effect in curing Helicobacter pylori infection.

METHODS

Seventy Hpylori-positive patients were given either eradication treatment consisting of 500 mg clarithromycin bid and 30 mg lansoprazole bid for 10 days plus 10 mL (400 mg) N-acetyl cysteine (NAC) liquid tid (AC group) or eradication treatment only (control group). The results were compared 1 month after the completion of the treatment.

RESULTS

Fifty-eight patients were available for statistical analysis. Of the 28 patients in the AC group, 14 (50.0%) eradicated the infection after treatment, whereas only 7 of 30 (23.3%) patients in the control group had negative results. The difference between the AC group and the control group was statistically significant (P = 0.034). In both groups, there was no difference in the number of smokers and in the eradication rates between smokers and nonsmokers. Eradication treatment with or without NAC caused no significant side effects in either group.

CONCLUSIONS

Our findings suggest that NAC has an additive effect on the eradication rates of H pylori obtained with dual therapy with lansoprazole and clarithromycin. NAC does not have any known activity against H pylori, but it may improve the delivery of antibiotics at the site of infection due to its ability to reduce the thickness of the mucus.

Is a long-term ranitidine-based triple therapy against Helicobacter pylori only a heritage of the past? A prospective, randomized clinicopharmacological study

BACKGROUND

Acid suppression plus two antibiotics is currently considered the gold standard anti-Helicobacter pylori treatment, but the effective role of gastric antisecretory drugs is still poorly understood.

AIMS

To compare a 14-day ranitidine-based triple regimen against Helicobacter pylori with one based on omeprazole, and to study the influence of antisecretory drugs on metronidazole pharmacokinetics in human plasma.

METHODS

A total of 150 dyspeptic H. pylori-infected patients were randomized for ranitidine 300 mg b.d. (RCM group) or omeprazole 20 mg b.d. (OCM group) 14-day triple therapy, with clarithromycin 500 mg b.d. and metronidazole 500 mg b.d. On the eighth day of therapy, metronidazole pharmacokinetics was studied in plasma by high-performance liquid chromatography. The pharmacokinetic parameters (terminal half-life, area under the curve, peak-plasma level, peak time) of metronidazole were computed using standard non-compartmental methods. H. pylori status was monitored before and 4 weeks after the end of therapy by histology, serology and rapid urease test.

RESULTS

On an intention-to-treat basis, eradication rates were 91 and 76% for the RCM and OCM groups respectively (P < 0.02). Significantly different pharmacokinetic parameters of metronidazole were found between the groups: peak-plasma level (P < 0.01) and area under the curve (P < 0.02).

CONCLUSION

Our results show that the RCM regimen was more effective than that based on OCM and that the antisecretory drugs affected metronidazole availability, increasing the efficacy of ranitidine-based regimens.

Gastric juice, gastric tissue and blood antibiotic concentrations following omeprazole, amoxicillin and clarithromycin triple therapy

BACKGROUND

Amoxicillin and clarithromycin are key antibiotics in proton pump inhibitor-based Helicobacter pylori eradication therapies.

AIMS

To study gastric mucus and tissue concentrations and collect basic data about optimal antibacterial doses.

METHODS

Plasma, gastric mucosa and gastric juice antibiotic concentrations were measured following either low- or high-dose amoxicillin (750 or 1000 mg b.i.d.) and clarithromycin (400 or 500 mg b.i.d.) given in combination with omeprazole 20 mg bid to 12 male volunteers in an open crossover design. Gastric juice and mucosal biopsy collection was performed either 2 (n=6) or 6 hours (n=6) after dosing.

RESULTS

Amoxicillin concentrations 2 hours after high dosage were gastric juice > gastric body > antral mucosa > plasma. At 6 hours, plasma and gastric juice concentrations were still above the MIC for amoxicillin-susceptible bacteria but no antibiotic was detectable in mucosa samples. Clarithromycin concentrations after high dosage were gastric juice > mucosa > serum; all above the MIC for clarithromycin-susceptible bacteria at both 2 and 6 hours.

CONCLUSIONS

Both dosage regimens provided effective antibiotic concentrations in gastric juice at 2 hours. After dosing, both antibiotics demonstrated high gastric tissue concentrations via local diffusion while clarithromycin also provided sustained delivery (6 hours) via gastric mucosa penetration.

Quantification of clarithromycin, its 14-hydroxy and decladinose metabolites in rat plasma, gastric juice and gastric tissue using high-performance liquid chromatography with electrochemical detection

A rapid, selective and sensitive HPLC assay has been developed for the simultaneous analysis of clarithromycin, its 14-hydroxy-clarithromycin metabolite, and its decladinose acid degradation product, in small volumes of rat gastric juice aspirate, plasma and gastric tissue. Sample were extracted with n-hexane/2-butanol (4:1) and the internal standard was roxithromycin. A Kromasil ODS 5 micrometer(75x4.6 mm I.D.) column was used with a mobile phase consisting of acetonitrile/aqueous phosphate buffer (pH 7, 0.086 M) (45:55 v/v). The column temperature was 30 degrees C and coulometric detection was used at 850 mV using a screen voltage of 600 mV. The analysis time was less than 8 min. The limits of quantitation for clarithromycin, 14-OH clarithromycin and decladinose clarithromycin were 0.15 microgram ml(-1) or lower in plasma (0.05 ml); 0.16 microgram ml(-1) or lower in gastric juice (0.2 ml); and 0.51 microgram g(-1) or lower for gastric tissue (0.25 g). The method was linear up to at least 20.3, 15.4 and 12.5 microgram ml(-1) for clarithromycin, 14-OH-clarithromycin and decladinose, respectively, in gastric juice aspirate and plasma and up to 40.6, 30.9 and 25.0 microgram g(-1) in gastric tissue. The assay was applied to the measurement of clarithromycin, 14-OH-clarithromycin and, for the first time, decladinose clarithromycin in pharmacokinetic studies of gastric transfer of clarithromycin in individual rats.