Pharmacokinetic and pharmacodynamic interactions between omeprazole and amoxycillin in Helicobacter pylori-positive healthy subjects.

BACKGROUND: Omeprazole with amoxycillin has been used to treat Helicobacter pylori infection. It was speculated that omeprazole-induced hypoacidity enhances the antibacterial activity of amoxycillin. Limited information exists about intragastric pH and bioavailability of amoxycillin during combination therapy. No data are available about possible effects of the antibiotic on the pharmacokinetics and pharmacodynamics of omeprazole. METHODS: The study was performed in a three-way cross-over double-blind design. After a run-in period on placebo with a baseline intragastric pH-metry, 24 H. pylori-positive healthy subjects were randomly dosed with amoxycillin 750 mg b.d. + placebo, amoxycillin 750 mg b.d. + omeprazole 40 mg b.d. and omeprazole 40 mg b.d. + placebo for 5 days. On the last day of each regimen intragastric pH-metries were performed, and blood samples taken for omeprazole and amoxycillin serum profiles. RESULTS: Amoxycillin monotherapy had no acid-inhibiting effect. Median pH during combined dosing was significantly lower, compared to omeprazole monotherapy (P < 0.01). Mean serum concentrations of omeprazole and amoxycillin given alone or in combination were not different. CONCLUSIONS: High-dose omeprazole does not alter the pharmacokinetics of amoxycillin. The significantly lower intragastric pH during combination therapy might be due to the H. pylori-suppressive effect of this treatment.

Energetics of nutrition and polyamine-related tumor growth alterations in experimental cancer.

The aim of this study was to evaluate whether food intake modulates experimental tumour growth by acute alterations in the energy state and blood flow of the tumour, and if so whether such changes are related to alterations in the enzyme ornithinedecarboxylase (ODC) and DNA synthesis. Inbred mice (C57BL/J) bearing a syngeneic undifferentiated and rapidly growing tumour were used. The tumour levels of high energy phosphates were measured in vivo by 31-P-NMR spectroscopy and biochemically following tissue extraction. DNA synthesis was estimated by measuring the incorporation of bromodeoxy-uridine into tumour DNA. Difluoro-methylornithine (DFMO) was used to inhibit ODC-activity. Tumour blood flow was estimated by a 132Xe local clearance technique. Tumour progression was associated with a significant decrease in tumour tissue high energy phosphates. Acute starvation decreased DNA-synthesis and tumour energy charge as well as its PCr/Pi which were rapidly normalised during subsequent refeeding. These changes were related to similar alterations in tumour blood flow. The inorganic phosphate (Pi) resonance and the resonances in the phosphomonoester (PME) region were considerably increased in tumour tissue. Inhibition of ODC-activity by DFMO decreased DNA-synthesis, which was associated with a secondary increase in tumour high energy phosphates probably due to a lowered energy demand for tumour cell division. The results demonstrate that host undernutrition was translated into retarded tumour growth associated with a decrease in the energy state and blood flow of the tumour. The results have bearing for the evaluation and planning of all treatment protocols with potential influence on food intake in experimental tumour-bearing animals.

24-hour intragastric acidity and plasma gastrin during long-term treatment with omeprazole or ranitidine in patients with reflux esophagitis.

The reduction in intragastric acidity and the subsequent increase in plasma gastrin were compared during long-term treatment with either omeprazole or ranitidine in 19 patients with erosive reflux esophagitis. The patients received 40 mg omeprazole in the morning or 300 mg ranitidine twice daily. After healing, half the dose was given as maintenance treatment for 1 year. Intragastric acidity and plasma gastrin were measured 24 h before entry and monthly with the high dose and after 1, 6, and 12 months with the low dose. Omeprazole reduced intragastric acidity more effectively than ranitidine (p less than 0.001). This difference in efficacy was more pronounced during the daytime. Plasma gastrin increased more after omeprazole than after ranitidine (p less than 0.01), and both drugs showed a normal postprandial response and approached fasting levels before the next dose. During long-term treatment with 20 mg omeprazole in the morning no progressive alterations were observed in 24-h intragastric acidity or plasma gastrin.