Pharmacodynamic Effects of Single Doses of Rabeprazole 20 Mg And
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Alimentary Pharmacology & Therapeutics Pharmacodynamic effects of single doses of rabeprazole 20 mg and pantoprazole 40 mg in patients with GERD and nocturnal heartburn S.WARRINGTON*,K.BAISLEY*,D.LEE*,K.LOMAX ,B.DELEMOSà,M.BOYCE*&A.MOROCUTTI§ *Hammersmith Medicines Research SUMMARY Ltd, Central Middlesex Hospital, London, UK; Medical Affairs, Eisai Background Inc., Teaneck, NJ, USA; àPriCara, Unit Rabeprazole and pantoprazole are both used for symptomatic treatment of Ortho-McNeil Inc., Raritan, NJ, USA; §Medical Affairs, Eisai Ltd, of gastro-oesophageal reflux disease (GERD). Speed and duration of acid London, UK suppression and intensity of effect after a single dose may be important pharmacodynamic properties in clinical use. Correspondence to: Dr S. Warrington, Hammersmith Aim Medicines Research Ltd, Central Middlesex Hospital, Acton Lane, To compare antisecretory effects of single doses of rabeprazole and pan- London NW10 7NS, UK. toprazole in patients with GERD and a history of nocturnal heartburn. E-mail: [email protected] Methods An open-label, randomized, two-way crossover, clinical pharmacology Publication data Submitted 30 August 2006 study was conducted. Twenty-nine Helicobacter pylori-negative GERD First decision 5 September 2006 patients (17 men, mean age 44 years), with a history of nocturnal heart- Resubmitted 18 October 2006 burn (mean frequency 4.7 episodes/week), received a single dose of Accepted 6 November 2006 rabeprazole 20 mg or pantoprazole 40 mg, with a 14-day ‘washout’. In- tragastric pH was recorded continuously from 24 h before to 24 h after dosing. Results Mean area under the intragastric pH–time curve (AUC) was significantly higher after dosing with rabeprazole 20 mg than with pantoprazole 40 mg in all time intervals analysed, including night (P £ 0.02). Mean percentage time with pH > 3 and >4 was significantly greater after rabeprazole than pantoprazole in all time intervals (P £ 0.004). Conclusion In GERD patients with nocturnal heartburn, a single oral dose of rabep- razole 20 mg increased intragastric pH more than pantoprazole 40 mg did throughout the 24 h after dosing. Aliment Pharmacol Ther 25, 511–517 ª 2007 The Authors 511 Journal compilation ª 2007 Blackwell Publishing Ltd doi:10.1111/j.1365-2036.2006.03196.x 512 S. WARRINGTON et al. mass index of 18.0–30.9 kg/m2 and were either non- INTRODUCTION smokers or smoked £5 cigarettes/day. All were negat- Proton pump inhibitors (PPIs) are now considered to be ive for H. pylori by serology and 13C-urea breath test the first-line treatment for gastro-oesophageal reflux (Helicobacter diagnostic test kit; Kestrel Healthcare Ltd, disease (GERD). Treatment efficacy is strongly correla- Basingstoke, UK). They were not allowed to take pre- ted with the degree and duration of acid suppression scription medicines during the 28 days before the start 1,2 over 24 h. GERD patients who experience nocturnal of the study, but an H2-blocker or PPI was allowed up symptoms may experience profound impairment of to 14 days before the start of the study. Oral contra- physical health, daytime function and emotional well- ceptives were allowed in women. Over-the-counter being, as demonstrated by measures of mental and medicines were not allowed within 7 days before the physical well-being, pain and oesophageal erosion.3 start of the study (with the exception of paracetamol), Suppression of nocturnal acidity may be particularly but antacid preparations were allowed up to 3 days important for symptom relief in such patients. before the start of the study. There are pharmacological differences among the PPIs after a single dose that may have implications for Ethics their clinical efficacy. For example, although all PPIs are strong inhibitors of gastric acid at steady state, The study proposal was reviewed and approved by the rabeprazole may suppress acid output more potently Brent Medical Ethics Committee. All subjects gave after a single dose.4,5 Such pharmacological differ- written informed consent. ences may also have implications for the control of nocturnal acidity. Study design Both pantoprazole and rabeprazole are used to treat patients with night-time reflux symptoms. Some This study was an open-label, randomized, two-way authors have suggested that, as pantoprazole has a crossover design. Subjects were resident at the study longer half-life than many other PPIs, it might be unit for two 3-day study periods separated by a wash- more effective at relieving nocturnal symptoms.3 out period of at least 14 days. After an overnight fast, Our study was designed to compare the antisecretory subjects were given a single dose of either rabeprazole effects of single doses of rabeprazole 20 mg and pan- 20 mg or pantoprazole 40 mg, with 100 mL of water. toprazole 40 mg in Helicobacter pylori-negative sub- The order of treatment with rabeprazole or pantopraz- jects who had a clinical diagnosis of GERD and a ole was randomized using an SAS program (SAS for history of nocturnal heartburn. Twenty milligrams of Windows, version 6.12; SAS Institute, Cary, NC, USA). rabeprazole and 40 mg of pantoprazole are the recom- Intragastric pH was measured from 24 h before dosing mended daily doses of each drug for oesophagitis heal- (day 0) until 24 h after dosing. Subjects had standard ing and symptom relief. Although there are numerous meals and drinks at 1, 4 and 10 h, and went to bed studies of the effect of PPIs on intragastric pH at steady (became supine) at around 14 h, after dosing on day 1, state, there are few published reports of the pharmaco- and at the corresponding times on day 0. Alcoholic dynamic effects on the first day of therapy. drinks, caffeinated beverages, smoking, grapefruit and its juice, Seville orange and its juice, and strenuous exercise were not allowed during the interval from MATERIALS AND METHODS 48 h before day 0 until the end of each study period. On day 2, 24 h after the dose of study medication, the Subjects intragastric pH measurements were stopped, the naso- Subjects were H. pylori-negative men or women aged gastric electrode was removed and patients were dis- 18–70 years, with a clinical diagnosis of GERD and a charged after a brief physical examination, if all was history of nocturnal heartburn (‡1 episode/week). Sub- well. They returned 5–10 days after the last dose of jects were interviewed regarding the frequency of their study drug for a follow-up medical examination. symptoms. Endoscopy was not required as an entry Adverse events were recorded throughout the study. criterion. Subjects were deemed otherwise healthy on Subjects were questioned about adverse events at the basis of medical history, medical examination, 12- regular intervals during their stay at the study unit, lead ECG and laboratory safety tests. They had a body and at follow-up. ª 2007 The Authors, Aliment Pharmacol Ther 25, 511–517 Journal compilation ª 2007 Blackwell Publishing Ltd RABEPRAZOLE VS. PANTOPRAZOLE IN GERD PATIENTS 513 contained fixed effects for sequence, period and treat- Measurement of intragastric pH ment, and random effects for subject nested within Intragastric pH was recorded continuously on days 0 sequence. The response variable was AUC or percent- and 1. On day 0, after anaesthetizing the subject’s age time with pH > 3 or >4 on day 1; the day 0 value nostril with 1% lidocaine hydrochloride spray, we was included in the model as a covariate. Day 1 AUCs inserted a disposable antimony internal reference pH were log-transformed to conform to a normal distribu- electrode with surface markings of 1 cm (Zinetics tion, except for AUC11)14, which did not require trans- Medical, Salt Lake City, UT, USA). pH was monitored formation. Day 1 percentage time pH > 3 and >4 was during passage of the electrode down the oesophagus, arcsin-transformed. Statistical inference was based on through the gastro-oesophageal sphincter and into the transformed variables. the stomach. We confirmed entry of the electrode The study was powered to test the hypothesis of no into the stomach by a sharp fall in pH, usually to difference in AUC0)24 between rabeprazole and pan- less than 3.2. Next, the electrode was withdrawn toprazole. Based on variability data obtained from a slowly to about 40 cm; a sharp rise in pH identified similar study in healthy volunteers,5 a within-subject the point at which the electrode crossed the sphinc- standard deviation of intragastric pH AUC0)24 of about ter. We then advanced the electrode slowly to a final 40 000 pH units/s was assumed. It was thus estimated position 8–10 cm (depending on the subject’s height) that 30 evaluable patients would have 90% power to beyond the point at which the pH fell below 3. Intra- detect a difference of 34 588 pH units/s in AUC0)24 gastric pH was recorded every 6 s using a Flexilog between rabeprazole and pantoprazole, at a 5% signi- 2020 96-h recorder (Oakfield Instruments, Oxford, ficance level. If within-subject variability in intragas- UK), which had been precalibrated using buffers of tric pH AUC0)24 was as high as 47 000 pH units/s, pH 1.1 and 6.7, before passage of the electrode. The then 30 evaluable patients would give 80% power to recorded data were uploaded to a computer using detect the same difference. Flexisoft II software (Oakfield Instruments). RESULTS Statistical analysis Subjects The primary efficacy variable was the area under the intragastric pH–time curve during the period from Thirty-one subjects entered the study. One man took dosing on day 1 until 24 h afterwards (AUC0))24). The an H2-blocker 5 days before dosing, and one man had primary null hypothesis was that there is no difference to repeat period 1 because of a failure of the pH recor- between rabeprazole and pantoprazole in intragastric der; both subjects were excluded from the per-protocol pH AUC0)24 on day 1.