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Biomedical subjects

V Savarino

Publications and source records attributed to V Savarino.

At least 19 recordsLinked to original sources
PubMed1992

Mealtime versus nighttime acid inhibition. A clinical pharmacological study with ranitidine.

This study was carried out in order to compare the effects of mealtime and bedtime regimens of ranitidine on gastric acidity. Fifteen duodenal ulcer patients in clinical remission were randomized to receive in single-blind fashion either placebo, ranitidine 300 mg at night (2200 hr) or ranitidine 150 mg three times a day given before each of the three daily meals (1800, 0800 and 1200 hr). Over 24 hr, the two active treatments produced a significantly greater acid inhibition than placebo, while the single daily regimen was superior to the three times a day regimen of ranitidine in terms of both rise in pH values (P less than 0.001) and duration of action expressed as time spent above 3.0 pH units (P less than 0.05). The analysis of these two parameters during fractioned periods of the circadian cycle showed that the three divided doses of ranitidine were more effective during the daytime (P less than 0.01) and the evening (P less than 0.001), whereas the bedtime dose of ranitidine was superior during the night (P less than 0.0001). Thus a short-lasting antisecretory action, which is, however, capable of fully controlling the high acidity of postprandial periods, might be the key to understanding the results of several recent clinical trials in which the suppression of daytime gastric acidity has been shown to promote similar or even faster duodenal ulcer healing rates than the suppression of nocturnal acidity.

Adult↗
PubMed1992

Duration of acid suppression in H2-antagonist nonresponders.

We monitored 24-hour gastric acidity in 16 resistant duodenal ulcer patients treated with ranitidine 300 mg hora somni (9 cases) and famotidine 40 mg hora somni (7 cases) for 3 months. Data obtained in these patients were compared with those of a group of unselected duodenal ulcer patients who responded to a 4-week course of the same H2-antagonist regimens. In the time window 22.00-07.59 h there was a reduced effectiveness of ranitidine in nonresponder patients in terms of both mean pH levels (4.8 +/- 0.9 vs. 5.6 +/- 0.7, p < 0.04) and the mean duration of the antisecretory effect defined as the time spent in minutes above pH 3.0 (403 +/- 73 vs. 490 +/- 59, p < 0.02). Also, the action of famotidine was diminished in nonresponder patients in the same time interval as regards both pH values (4.1 +/- 1.6 vs. 5.7 +/- 0.6, p < 0.03) and the duration in minutes (329 +/- 163 vs. 473 +/- 45, p < 0.05). The analysis of all individual nonresponder patients shows that there was a certain variability in the duration of acid suppression: the majority of them had an adequate nocturnal acid inhibition, while in some cases of both the ranitidine and the famotidine subgroups, acid inhibition lasted only few hours or did not occur at all. At present, it is not possible to distinguish with certainty two different subsets of H2-antagonist nonresponders because of the small size of the population studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug Tolerance↗
PubMed1992

Optimizing the information obtained from continuous 24-hour gastric pH monitoring.

Our objective in performing this study was to determine the best way to summarize experimental data obtained from 24-h continuous intragastric pH-metry. For this purpose, we reviewed 605 circadian intragastric pH recordings performed under different clinical conditions. Included were 82 normal subjects, 126 patients with active duodenal ulcer, 272 ulcer patients in clinical remission treated with a single bedtime dose (at 10 PM) of various H2 antagonists and 125 patients with active ulcer treated with a single morning dose (8 AM) of omeprazole. For each group, we calculated the time spent at different pH levels scaled with 0.1 incremental steps in three different time intervals: 24 h (5 PM to 4:59 PM), daytime (8 AM to 7:59 PM), and nighttime (8 PM to 7:59 AM). Then we calculated the mean and the median pH, as well as the time spent in min greater than 3.0 pH units over a mainly drug-related time window (8 PM to 7:59 AM) for each treatment and its respective placebo group. The mean and the median pH, as well as the time spent in minutes greater than 1.2 pH units over 24 h were also calculated for the untreated groups of normal subjects and duodenal ulcer patients. Considering the individual pH recordings, bi- or plurimodal density distributions of pHs were found in more than 90% of the 605 subjects, no matter the time window and the clinical condition examined, and log-normal distributions were found in only three cases. Considering the groups instead of single pH recordings, conversely, normal subjects and duodenal ulcer patients showed average left-skewed unimodal density distributions, whereas bimodal patterns were the rule in the groups of patients treated with H2 antagonists and omeprazole. The time spent greater than 3.0 pH units was the most powerful acidity index in assessing drug effectiveness in the various subsets of antisecretory compounds, in that the Student's t test values obtained with this variable were almost invariably higher than those obtained with the mean and median pH levels. Also, the time spent greater than 1.2 pH units was the most powerful summary variable in differentiating normal subjects from duodenal ulcer patients (p less than 0.01, compared with the mean and median pH). We conclude that the time spent above a given pH threshold of interest is a more accurate index than the mean and median pH in summarizing gastric acidity changes under all clinical conditions, and this is because it better represents the experimental pH measurements from which it comes.

Circadian Rhythm↗
PubMed1991

[Esophageal pH monitoring: factors influencing the definition of normality].

Prolonged esophageal pH-metry has become an irreplaceable investigative tool in diagnosing gastroesophageal reflux. Given the presence of episodes of acid reflux even under physiological circumstances, it is of primary importance to define the range of normal values in order to correctly identify the condition of disease. This task is complicated by the lack of an absolute and objective marker of normality, to be referred to, and by the number of variables that can influence the measurement of the esophageal pH. Among the most important factors that can influence this test there are age, physical exercise, posture and diet. Even voluptuary habits, such as smoking and alcohol intake, could be detrimental in this respect. Then there are many technical factors that can act as sources of relevant errors in measuring and calculating the parameters chosen to discriminate normality from abnormality, the most important ones being as follows: defective electrodes, electrodes that have not been calibrated accurately, electrodes positioned erroneously, interference with the pH readings by mucus, food, aiming at the walls of the esophagus, inconsistent sampling rates among the recording equipment, differences in the software used to automatically analyze the experimental data, failure to recognize and consequently to eliminate the artifacts present in the pH-metry tracings, inadequate "in situ" repeatability of the esophageal pH measurements on the part of paired electrodes that simultaneously record the pH.

Esophagus↗
PubMed1991

Single morning and nightly doses of ranitidine 300 mg: an appraisal of their antisecretory effects by continuous pH monitoring.

Gastric acidity of 12 patients with healed duodenal ulcers was continuously monitored over 24 h in order to assess the antisecretory effects of two different administration times of a single daily dose of ranitidine 300 mg. Each patient orally received either (a) placebo at 08.00 h and 22.00 h; (b) ranitidine 300 mg at 08.00 h and placebo at 22.00 h, or (c) placebo at 08.00 h and ranitidine 300 mg at 22.00 h in randomized and double-blind fashion. Each medication was administered on three separate occasions, with intervals of at least 1 week. Both the morning and the bedtime doses of ranitidine were significantly superior (p less than 0.001) to placebo in controlling 24-hour gastric acidity, while, in the same period, ranitidine nocte was more effective (p less than 0.001) than ranitidine mane. During the night, bedtime ranitidine caused more acid inhibition (p less than 0.001) than morning ranitidine, but the opposite (p less than 0.01) occurred during the daytime. This study shows that the antisecretory effect of morning ranitidine during the daytime is less consistent than that achieved by bedtime ranitidine during the nocturnal period. As similar rates of duodenal ulcer healing have recently been achieved with morning and conventional nighttime administration of H2 antagonists, it becomes clear that antisecretory drugs can also be beneficial with an acid inhibition which is shorter-lasting than that which was previously thought to be necessary or, alternatively, that also daytime acidity is important in ulcerogenesis.

Adult↗
PubMed1991

Lack of gastric acid rebound after stopping a successful short-term course of nizatidine in duodenal ulcer patients.

To assess whether there is rebound of gastric acidity after a short-term course of H2-receptor antagonists, we performed a 24-h in situ pH monitoring on 17 duodenal ulcer patients before, during, and after completing 4 wks' treatment with nizatidine 300 mg at bedtime (2200 h). Three around-the-clock continuous intragastric pH-metries were carried out the day before beginning treatment, at the end of the nizatidine course, and 67 h after the last dose of the drug was given. Nizatidine produced mean pH values that were significantly higher (p less than 0.001) than those of the pretreatment profile during both the whole 24-h period and the nighttime (2400-0759), and this confirms that it effectively inhibited gastric acidity. Conversely, there was no significant difference between the acidity indexes of pH profiles obtained before dosing and after discontinuing treatment in any of the time intervals considered. Therefore, it appears that a short term course of nizatidine therapy does not cause rebound hyperacidity in duodenal ulcer patients.

Adult↗
PubMed1991

24-hour study of gastric acidity in normal subjects and in cholecystectomized patients using continuous pH monitoring.

The circadian pattern of gastric acidity was assessed in 53 normal subjects and in 33 patients with prior cholecystectomy using continuous pH monitoring. The 24-hour and nocturnal median pH values were significantly higher in cholecystectomized patients than in controls (p less than 0.03 and p less than 0.001, respectively). In the operated group there were higher median pHs also in the after-dinner (p less than 0.003) and after-lunch (p less than 0.01) periods, while no difference between the two populations was observed after breakfast. The percentage of 24-hour pH readings above 4.0 units was markedly higher (p approximately 0) in postcholecystectomy patients. We conclude that circadian gastric acidity is reduced in cholecystectomized patients with respect to healthy subjects, both in nocturnal and postprandial states. Episodes of duodenogastric reflux may be responsible for this, but impaired acid production related to advanced age (14 patients were more than 60 years old) or to fundic chronic atrophic gastritis (5 cases) may also account for the elevation of pH values in our postcholecystectomy patients.

Cholecystectomy↗
PubMed1990

Inaccuracy of hourly sampled pH measurements in describing the effect of antisecretory drugs on circadian gastric acidity.

This study was carried out in order to verify whether gastric pH measurements obtained with continuous monitoring are more accurate in assessing the pharmacodynamic properties of antisecretory drugs than those obtained with the traditional hourly nasogastric aspiration method. Accordingly, we compared the most commonly used acidity indexes (median of pHs and mean of [H+]s) and the total circadian time spent above 4.0 pH units, all of which were calculated from both raw data sampled at rates of a few seconds with modern apparatus and data obtained from the same profiles scanned punctually at a 60 minute rate. The analysis referred to 231 continuous gastric pH-metries which were performed over the circadian period to evaluate the acid inhibitory effects of different doses and dosage regimens of various H2-antagonists. In the population as a whole, the numbers and percentages of subjects, whose 60-minute sampled medians of pHs and means of [H+]s differed by less than +/- 10% from those obtained from raw fast-acquired data, were 107 (46%) and 34 (15%), respectively. There was even less agreement in the case of the circadian time above 4.0 pH units (26 cases = 11%). No statistical difference (P = .7) between the concordance rates of each variable in the three groups was observed. Considered simultaneously, there was concordance of the above three indexes in only seven out of the 231 cases. These results show that the hourly sampling rate fails to represent adequately gastric acidity changes induced by antisecretory drugs, due to the scarcity of experimental points. The acidity indexes calculated from these slowly sampled data are inaccurate, especially when the means of [H+]s are considered, and the duration of action of the drug often is defined randomly.

Anti-Ulcer Agents↗
PubMed1990

Antimony and glass pH electrodes can be used interchangeably in 24-hour studies of gastric acidity.

Antimony and glass pH electrodes show almost identical experimental errors in continuously measuring buffer solutions at constant temperature over 24 hr. These errors are lower than the nominal quantization error of the instruments and are not properly described by the 24-hr drift determination. The addition of food particles to the solutions can induce severe reading artifacts. The longer response time reported in vitro of antimony electrodes when moving from pH 1 to pH 7 (3.4 sec vs 0.8 sec with glass electrodes) is irrelevant during in vivo pH-metry studies, because we found that the greatest absolute difference between raw fast acquired (4-6 sec) consecutive pH readings of two commonly used devices was 0.7 pH units in circadian profiles obtained from 413 subjects with various clinical conditions. In our in vivo studies, gastric acidity was monitored continuously with two side-by-side minielectrodes, which were variously combined (antimony-glass, A-G; antimony-antimony A1-A2; glass-glass, G1-G2) and applied on groups of 27 subjects matched for clinical condition. The 24-hr pH means and the 24-hr [H+] means calculated from the acidity profiles obtained with the three electrode combinations, lie on the identity line in each group. Using the Bland-Altman technique for assessing measurement agreement, the differences between the 24-hr pH means and the 24-hr [H+] means obtained with the three combined systems are similar (P = .903 and P = 0.824, respectively) and their 95% confidence limits are comprised within the range (+/-) of the reading error of the measuring systems (namely, +/- 0.3 pH units and +/- 12 mmol/liter in terms of [H+]).(ABSTRACT TRUNCATED AT 250 WORDS)

Antimony↗