Transfer of clarithromycin to gastric juice is enhanced by omeprazole in Helicobacter pylori-infected individuals

Pharmacokinetic drug interactions of antimicrobial drugs: a systematic review on oxazolidinones, rifamycines, macrolides, fluoroquinolones, and Beta-lactams

Like any other drug, antimicrobial drugs are prone to pharmacokinetic drug interactions. These drug interactions are a major concern in clinical practice as they may have an effect on efficacy and toxicity. This article provides an overview of all published pharmacokinetic studies on drug interactions of the commonly prescribed antimicrobial drugs oxazolidinones, rifamycines, macrolides, fluoroquinolones, and beta-lactams, focusing on systematic research. We describe drug-food and drug-drug interaction studies in humans, affecting antimicrobial drugs as well as concomitantly administered drugs. Since knowledge about mechanisms is of paramount importance for adequate management of drug interactions, the most plausible underlying mechanism of the drug interaction is provided when available. This overview can be used in daily practice to support the management of pharmacokinetic drug interactions of antimicrobial drugs.

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.

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.

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.

Helicobacter pylori: factors affecting eradication and recurrence

Proton pump inhibitors play an important role in increasing the bioavailability of antibiotics in the gastric mucus by altering gastric volumes and increasing the stability of some antibiotics, e.g., clarithromycin. Increasing the doses of potent proton pump inhibitors has small effects on eradication rates but there may be differences between proton pump inhibitors that need further study.

EFFICACY AND LONG-TERM OUTCOME OF GASTRITIS THERAPY IN CHEETAHS (ACINONYX JUBATUS)

A prospective clinical trial evaluating efficacy and long-term outcome of treatments for lymphoplasmacytic gastritis in cheetahs (Acinonyx jubatus) was conducted. The study evaluated efficacy of 11 different antibiotic and antiinflammatory treatment protocols in 32 cheetahs (19 male, 13 female) for reducing gastric inflammation and Helicobacter colonization and monitored the course of disease through histologic grading of gastric biopsies. All cheetahs were biopsied up to I wk before treatment and then rebiopsied within 1 mo after treatment. Most animals were reassigned to a second treatment regimen within 6 mo. Each animal received from one to three treatments during the study period. After the trial, gastric biopsies were obtained from each cheetah annually until death or transfer from the facility to assess disease progression. The trial and follow-up period spanned 10 yr. At onset of the trial, all 32 cheetahs had some degree of gastritis, and 26 cheetahs (81%) were colonized with Helicobacter. Inflammatory lesions worsened regardless of treatment or the presence of Helicobacter. No treatment had a significant effect on inflammatory changes except the lansoprazole/clarithromycin/amoxicillin treatment group, which produced a short-term decrease in inflammation when compared to controls. Prednisone had no effect on gastric inflammation. Overall, 65% of colonized cheetahs were initially cleared of histologic evidence of Helicobacter by treatment, with short-term eradication occurring in 100% of the animals treated with omeprazole/clarithromycin/amoxicillin or tetracycline/metronidazole/Pepto-Bismol for 28 days. Long-term follow-up of treated animals in this study clearly demonstrated that these treatments had little effect on life-long progression of gastritis or on Helicobacter burden in individual cheetahs, although some treatments provided short-term reduction in gastritis and Helicobacter. These results provide evidence that Helicobacter alone is not the cause of gastritis in cheetahs and do not support the use of antibacterial treatments in cheetahs unless significant clinical signs (e.g., frequent vomiting/regurgitation, weight loss) are apparent.

Diagnostic methods for Helicobacter pylori detection and eradication

Helicobacter pylori is the principal cause of peptic ulcer disease and an important risk factor for the development of gastric cancer. The efficacy of 1 week triple therapies, which often have eradication rates of>90%, is undermined by poor patient compliance and bacterial antimicrobial resistance. The development of new anti-H. pylori therapies presents enormous challenges to clinical pharmacologists, not only in the identification of novel targets, but also in ensuring adequate drug delivery to the unique gastric mucus niche of H. pylori. Animal models of H. pylori infection have been developed but their clinical validity has yet to be established. Vaccination, to prevent or treat infection, has been demonstrated in animal models, but human studies have not been so encouraging.

Amoxicillin and ampicillin are not transferred to gastric juice irrespective of Helicobacter pylori status or acid blockade by omeprazole

BACKGROUND

The effects of proton pump inhibitors and Helicobacter pylori infection on the distribution of drugs used for the eradication of the bacteria are poorly understood.

AIM

The aim of this study was to investigate the effects of a 7-day administration of 20 mg of omeprazole on the pharmacokinetics of amoxicillin and ampicillin in the plasma, saliva and gastric juice of individuals with and without H. pylori infection.

METHODS

Fifty-four healthy volunteers without endoscopic lesions were enrolled. Twenty-six volunteers were included in the amoxicillin study and 28 individuals in the ampicillin study. Each study had an open randomized two-period crossover design and a 21-day washout period between phases. Plasma, saliva and gastric juice concentrations of amoxicillin and ampicillin in subjects with and without omeprazole pre-treatment were measured by reversed-phase HPLC using UV detection.

RESULTS

Neither pre-treatment with omeprazole nor H. pylori infection interfered with the plasma bioavailability of amoxicillin or ampicillin, as assessed by the AUC0-2 h. Neither ampicillin nor amoxicillin were detected in saliva or gastric juice in any study phase.

CONCLUSION

Short-term treatment with omeprazole does not interfere with the pharmacokinetics of amoxicillin or ampicillin. Our results also exclude the presence of a transfer mechanism for amoxicillin or ampicillin from the plasma to the gastric lumen.

Effect of acid secretion blockade by omeprazole on the relative bioavailability of orally administered furazolidone in healthy volunteers

AIMS

The administration of omeprazole may interfere with the absorption of orally administered drugs by reducing gastric pH and hence tablet dissolution. The aim of this study was to investigate the effects of a 5 day administration of omeprazole on the pharmacokinetics of furazolidone.

METHODS

Eighteen healthy (nine male and nine female) volunteers were selected. The study had an open randomized two-period crossover design with a 21 day washout period between the phases. Serum concentrations of furazolidone were measured by reversed-phase h.p.l.c. with ultraviolet detection.

RESULTS

Administration of omeprazole caused a significant reduction of Cmax [0.34 microg x ml(-1) (range 0.25-0.43) vs 0.24 microg x ml(-1) (range 0.15-0.34)] with no significant delay in absorption tmax [2.5 h (range 1.85-3.0) vs 2.4 h (range 2.06-2.71)].

CONCLUSIONS

Furazolidone was rapidly absorbed after oral administration. Short-term treatment with omeprazole did alter the relative bioavailability of this drug, probably through an effect on absorption kinetics or first-pass metabolism.