PubMed · 12082341
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C A Desai, B D Samant. Rabeprazole.. https://pubmed.ncbi.nlm.nih.gov/12082341/
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The first-order UV-derivative spectrophotometry, applying zero-crossing method was developed for the determination of omeprazole (OM), omeprazole sulphone (OMS), pantoprazole sodium salt (PANa), and N-methylpantoprazole (NPA) in methanol-ammonia 4.0% v/v, where the sufficient spectra resolutions of drug and corresponding impurity were obtained, using the amplitudes 1D(304), 1D(307), 1D(291.5) and 1D(296.5), respectively. Method showed good linearity in the ranges (microg ml(-1)): 1.61-17.2 for OM; 2.15-21.50 for OMS; 2.13-21.30 for PANa and 2.0-20.0 for NPA, accuracy and precision (repeatability and reproducibility). The experimentally determined values of LOD (microg ml(-1)) were 1.126; 0.76; 0.691 and 0.716 for OM, OMS, PANa and NPA, respectively. The obtained values of 2.91% w/w for OMS and 3.58% w/w for NPA in the presence of their parent drug, by applying the method of standard additions, point out the usage of the proposed method in stability studies. Zero-crossing method in the first-order derivative spectrophotometry showed the impurity-drug intermolecular interactions, due to the possible intermolecular hydrogen bonds, confirmed by divergences of experimentally obtained amplitudes for impurities OMS and NPA in comparison to expected values according to regression equations of calibration graphs.
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BACKGROUND: In gastro-oesophageal reflux disease (GERD) subjects treated with a gastric anti-secretory agent, it is not known whether there is a relationship between heartburn severity and oesophageal acid exposure. METHODS: Oesophageal pH and heartburn severity were determined in 27 GERD subjects at baseline and on days 1, 2 and 8 of treatment with 20 mg omeprazole or 20 mg rabeprazole in a randomized, two-way crossover fashion. RESULTS: Receiver operating characteristic (ROC) analysis was used to determine values for heartburn severity that gave optimal cut-off points for distinguishing between normal and pathologic oesophageal reflux. Using these cut-off points, we found that the probability of no pathologic oesophageal reflux (Y) could be best fitted by an exponential equation: Y = a(e-bX) + c, where a, b and c are constants and X is the value of heartburn severity. There was close agreement between predicted and observed percentages of subjects with pathologic oesophageal reflux during different days of treatment. CONCLUSIONS: In GERD subjects treated with a proton-pump inhibitor, the value of heartburn severity following a single standard meal can predict the likelihood of pathologic oesophageal reflux over the entire 24-h period.