Cardiovascular effects of ranitidine and cimetidine during acute myocardial ischaemia in anaesthetized dogs

Effect of Histamine H2 Receptor Antagonists on All-Cause Mortality in Critically Ill Patients With Essential Hypertension: A Retrospective Cohort Study

Previous studies found that histamine H2 receptor antagonists (H2RAs) had blood pressure lowering and cardioprotective effects, but the impact of H2RAs on the survival outcomes of critically ill patients with essential hypertension is still unclear. The aim of this study was to investigate the association of H2RAs exposure with all-cause mortality in patients with essential hypertension based on Medical Information Mart for Intensive Care III database. A total of 17,739 patients were included, involving 8482 H2RAs users and 9257 non-H2RAs users. Propensity score matching (PSM) was performed to improve balance between 2 groups that were exposed to H2RAs or not. Kaplan-Meier survival curves were used to compare the cumulative survival rates and multivariable Cox regression models were performed to evaluate the association between H2RAs exposure and all-cause mortality. After 1:1 PSM, 4416 pairs of patients were enrolled. The results revealed potentially significant association between H2RAs exposure and decreased 30-day, 90-day, and 1-year mortalities in multivariate analyses (HR = 0.783, 95% CI: 0.696-0.882 for 30-day; HR = 0.860, 95% CI: 0.778-0.950 for 90-day; and HR = 0.883, 95% CI: 0.811-0.961 for 1-year mortality, respectively). Covariate effect analyses showed that the use of H2RAs was more beneficial in essential hypertension patients with age ≥ 60, BMI ≥ 25 kg/m2, coronary arteriosclerosis, stroke, and acute kidney failure, respectively. In conclusion, H2RAs exposure was related to lower mortalities in critically ill patients with essential hypertension, which provided novel potential strategy for the use of H2RAs in essential hypertension patients.

Effects of histamine H2-receptor blockade on the cardiovascular reflex response to lower-body negative pressure in man

The role of histamine H2-receptors in cardiovascular control is unknown. In seven healthy volunteers, we studied how histamine H2-receptor blockade affected the reflex response to hypovolaemia induced by lower-body negative pressure (LBNP). In placebo-treated individuals, LBNP down to -40 mmHg did not change systolic pressure but increased diastolic pressure, heart rate, forearm vascular resistance, plasma noradrenaline concentration and plasma renin activity. After pretreatment with ranitidine, a specific histamine H2-receptor antagonist, the diastolic pressure rise no longer sufficed to maintain a constant systolic pressure during LBNP. Ranitidine pretreatment also attenuated the heart rate response and the rise in plasma renin activity induced by LBNP, but did not significantly change the reflex forearm vasoconstriction or the forearm plasma noradrenaline response. The results suggest that histamine H2-receptor blockade attenuates the reflex vasoconstrictor response to lower-body negative pressure. The mechanism behind this effect remains unknown, but the data do not support the idea that the effect is exerted in the skeletal muscle vascular bed.

Ventricular histamine concentrations and mast cell counts in the rat heart during acute ischaemia

The ventricular histamine concentrations and mast cell counts of naive and disodium cromoglycate-treated rats subjected to acute left coronary artery ligation under pentobarbitone anaesthesia were examined. In naive animals, there was a significant increase in the right ventricular histamine level at 2 min following left coronary artery ligation. Left ventricular histamine concentrations tended to decrease, and were significantly lower than those of the right ventricle at 5 min. However there were no significant changes in mast cell counts of the right or left ventricles after left coronary artery ligation. Treatment with disodium cromoglycate did not significantly alter the ventricular mast cell counts, interfere with the changes in ventricular histamine concentrations, or the occurrence of early ventricular arrhythmias and haemodynamic changes in response to acute left coronary artery ligation. It is suggested that the increase in the right and decrease in the left ventricular histamine concentrations during acute myocardial ischaemia involves mainly the non-mast cell stores, instead of mast cell sources, of cardiac histamine.

Ranitidine. An updated review of its pharmacodynamic and pharmacokinetic properties and therapeutic use in peptic ulcer disease and other allied diseases

Ranitidine, a histamine H2-receptor antagonist, is now well established as a potent inhibitor of gastric acid secretion effective in the treatment and prophylaxis of gastrointestinal lesions aggravated by gastric acid secretion. Therapeutic trials involving several thousands of patients with peptic ulcer disease confirm that ranitidine 300mg daily administered orally in single or divided doses is at least as effective as cimetidine 800 to 1000mg daily in increasing the rate of healing of duodenal and gastric ulcers. Similar dosages of ranitidine have been shown to relieve the symptoms of reflux oesophagitis and heal or prevent gastrointestinal damage caused by ulcerogenic drugs. Ranitidine 150mg orally at night maintains ulcer healing in the long term. Ranitidine has also demonstrated good results in the treatment of Zollinger-Ellison syndrome and in the prevention of aspiration pneumonitis when given prior to surgery and to pregnant women at full term. It may also have a place in the management of acute upper gastrointestinal bleeding and in the prevention of stress ulcers in the intensive care setting, although these areas require further investigation. Ranitidine has been used safely in obstetric patients during labour, in children, the elderly, and in patients with renal impairment when given in appropriate dosages. The drug is very well tolerated and is only infrequently associated with serious adverse reactions or clinically significant drug interactions. Even at high dosages, ranitidine appears devoid of antiandrogenic effects. Ranitidine is clearly comparable or superior to most other antiulcer agents in the treatment and prevention of a variety of gastrointestinal disorders associated with gastric acid secretion. With its favourable efficacy and tolerability profiles, ranitidine must be considered a first-line agent when suppression of gastric acid secretion is indicated.

Ranitidine-induced chest pain

A 45-year-old woman with no history of heart disease twice experienced chest pain after consuming a dose of ranitidine. The chest pain, which lasted about one hour, was substernal, left of midline, dull, and pounding. H2-receptors are present in cardiovascular tissues. Although several studies have not noted an effect of ranitidine on cardiac indices there have been case reports indicating a cardiac effect. There are no reports of chest pain associated with H2-blocker ingestion; however, both bradycardia and hypotension (reported effects) might cause chest pain. A discussion of the possible mechanisms is presented.

Ventricular arrhythmias parallel cardiac histamine efflux after coronary artery occlusion in the dog

Release of cardiac histamine by immunologic and pharmacologic stimuli is known to provoke ventricular arrhythmias. Augmented histamine efflux from ischemic myocardium has been proposed but remains controversial. The purpose of this study was to determine whether cardiac histamine efflux is precipitated by coronary artery occlusion and if so, whether histamine efflux is associated with the development of early ischemic ventricular arrhythmias. The left anterior descending coronary artery was occluded while recording a continuous electrocardiogram and coronary sinus blood was sampled frequently during the first 30 min of coronary artery occlusion in pentobarbital-anesthetized, open-chest dogs. Coronary sinus histamine concentration rose from a mean baseline of 0.06 +/- 0.10 ng/ml (+/- SD) before coronary artery occlusion to a mean peak of 0.61 +/- 0.40 ng/ml after coronary artery occlusion (p less than 0.0001; n = 14). The median peak coronary sinus histamine concentration was significantly greater in dogs that suffered ventricular fibrillation after coronary artery occlusion (n = 4) than in those that did not (n = 10) (0.86 ng/ml vs. 0.37 ng/ml; p = 0.05). The area under the coronary sinus histamine concentration-vs.-time curve ("total cardiac histamine efflux") correlated directly with the total number of ventricular premature contractions during the first 30 min after coronary artery occlusion (r = 0.81; p less than 0.005; n = 10), and with infarct size (r = 0.91; p less than 0.01; n = 6). Thus, during acute myocardial ischemia, the coronary sinus histamine concentration increases simultaneously with the development of early ischemic ventricular arrhythmias and in proportion to their severity.

Ventricular histamine concentrations and arrhythmias during acute myocardial ischaemia in rats

The relation between ventricular histamine concentrations and the occurrence of early ventricular arrhythmias during acute myocardial ischaemia was investigated in pentobarbitone-anaesthetized rats. There was significant decrease in the left, but not the right, ventricular histamine level at 5 min following acute left coronary artery ligation. Pretreatment with rhodanine caused remarkable reduction in ventricular histamine concentrations as well as significantly lower incidence and slower onset of ventricular tachycardia and fibrillation resulting from acute myocardial ischaemia. On the contrary, aminoguanidine pretreatment did not significantly alter ventricular histamine levels nor did it influence the occurrence of early ventricular arrhythmias induced by coronary artery ligation. The responses of blood pressure and heart rate to acute coronary artery ligation were not noticeably affected by rhodanine or aminoguanidine pretreatment. These findings support the hypothesis that histamine release from cardiac tissues may contribute to the genesis of early ventricular arrhythmias, but not to the changes in blood pressure and heart rate, during acute myocardial ischaemia.