Significance of a tetracycline and Pepto-Bismol interaction in the management of Helicobacter pylori-induced peptic ulcer disease

The ATP-binding cassette transporters and their implication in drug disposition: a special look at the heart

The passage of drugs across cell membranes dictates their absorption, distribution, metabolism, and excretion. This process is determined by several factors including the molecular weight of the compounds, their shape, degree of ionization, and binding to proteins. Accumulation of xenobiotics into tissues does not depend only on their ability to enter cells, but also on their ability to leave them. For instance, the role of efflux transporters such as ATP-binding cassette (ABC) proteins in the disposition of drugs is now well recognized. Actually, ABC transporters act in synergy with drug-metabolizing enzymes to protect the organism from toxic compounds. The most studied transporter from the ABC transporter superfamily, P-glycoprotein, was found to be overexpressed in tumor cells and associated with an acquired resistance to several anticancer drugs. P-glycoprotein, thought at first to be confined to tumor cells, was subsequently recognized to be expressed in normal tissues such as the liver, kidney, intestine, and heart. Even though information remains rather limited on the functional role of ABC transporters in the myocardium, it is hypothesized that they may modulate efficacy and toxicity of cardioactive agents. This review addresses recent progress on knowledge about the ABC transporters in drug disposition and more precisely their role in drug distribution to the heart.

A single drug for Helicobacter pylori infection: first results with a new bismuth triple monocapsule

OBJECTIVE

In this pilot study we investigated the efficacy and tolerability of a new monocapsule that contains a bismuth compound, tetracycline, and metronidazole. If proven to be effective, this monotherapy would turn the well-accepted multidrug regimen of standard bismuth-based triple therapy into an easy and more patient-friendly regimen. It can be used in patients allergic to penicillin.

METHODS

A total of 53 consecutive H. pylori-infected patients (30 with proven ulcer disease, 23 with gastritis only) from a single center were prescribed two monocapsules q.i.d. after the three meals and after an evening snack during 10 days. Each capsule contained 60 mg colloidal bismuth subcitrate (as Bi2O3 equivalent), 125 mg tetracycline, and 125 mg metronidazole. Repeat endoscopy with biopsies for urease test, Giemsa stain, and culture was carried out > or =5 wk later. Side effect data were collected.

RESULTS

One patient was lost to follow-up, two failed to respond, and 50 were cured. The intention-to-treat cure rate was 50 of 53 (94.4%, 95% CI 88.1-100%). Antibiotic sensitivity was available from 51 isolates. The cure rate in the metronidazole sensitive strains was 44 of 45 (97.8%, 95% CI: 93.5-100%), whereas it was four of five in the resistant strains. The regimen was well tolerated, with only two drop-outs (4%) because of side effects.

CONCLUSIONS

The new monocapsule is an inexpensive, well tolerated, and patient-friendly formulation of a bismuth based triple therapy. A 10-day course with this multidrug capsule reached a very high cure rate in metronidazole-sensitive strains. The number of cases with resistant strains was insufficient to allow firm conclusions about its efficacy in case of resistance. The results are in agreement with previous data with bismuth triple therapy using separate drugs. From the high cure rate, we can conclude that the new capsule dissolves adequately, with proper delivery of its ingredients at the site of action.

Pharmacokinetic considerations in the eradication of Helicobacter pylori

As Helicobacter pylori plays an important role in the aetiopathogenesis of peptic ulcer, therapeutic strategies aimed at maintaining long term remission have shifted from the control of intragastric pH to targeting H. pylori. According to recent international guidelines the clinical goals--rapid ulcer healing and prevention of relapse--can be best accomplished by combination therapy consisting of an antisecretory drug (proton pump inhibitor or ranitidine) and 2 antimicrobial agents (preferable amoxicillin, clarithromycin or metronidazole). When applying such multidrug regimens, possible synergy between the agents suggests that pharmacokinetic considerations might help to improve H. pylori eradication rates, which should be above 85 to 90% on an intention-to-treat basis. The present review summarises the pharmacokinetic properties and interaction potential of all drugs presently used in the various H. pylori eradication regimens, with emphasis on particular patient populations such as the elderly and those with renal impairment. The drugs considered are omeprazole, lansoprazole, pantoprazole, rabeprazole, ranitidine and ranitidine bismutrex, bismuth salts, amoxicillin, clarithromycin, azithromycin, roxithromycin, metronidazole, tinidazole and tetracycline. When addressing the clinically important questions of the efficacy, safety and costs of the recommended regimens, the impact of drug disposition on H. pylori eradication should not be neglected.