of heartburn Short-term and maintenance therapy of gastric and duodenal ulcers With nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce the risk of ulceration Proton-pump inhibitors (PPIs) are more effective for the prevention of NSAID-induced ulcers. Pathologic gastrointestinal (GI) hypersecretory conditions such as Zollinger–Ellison syndrome Gastroesophageal reflux disease (GORD or GERD) Erosive esophagitis Part of a multidrug regimen for H. pylori eradication to minimise the risk of duodenal ulcer recurrence Recurrent postoperative ulcer Upper GI bleeding For prevention of acid-aspiration pneumonitis during surgery, it can be administered preoperatively. The drug increases gastric pH, but generally has no effect on gastric volume. In a 2009 meta-analysis comparing the net benefit of PPIs and ranitidine to reduce the risk of aspiration before anaesthesia, ranitidine was found to be more effective than PPIs in reducing the volume of gastric secretions. Ranitidine may have an anti-emetic effect when administered preoperatively. Prevention of stress-induced ulcers in critically ill patients Used together with diphenhydramine as secondary treatment for anaphylaxis; after first-line epinephrine. Contraindication Ranitidine has been discontinued globally, according to the NHS, and is contraindicated due to excess cancer risk and the ready availability of H2 antagonist and PPI alternatives. Adverse effects These adverse effects for ranitidine have been reported as events in clinical trials: Central nervous system Rare reports have been made of ranitidine causing malaise, dizziness, somnolence, insomnia, and vertigo. In severely ill, elderly patients, cases of reversible mental confusion, agitation, depression, and hallucinations have been reported. Cardiovascular Arrhythmias such as tachycardia, bradycardia, atrioventricular block, and premature ventricular beats have also been reported. Gastrointestinal All drugs in the H2 receptor blocker class of medicines have the potential to cause vitamin B12 deficiency, secondary to a reduction in food-bound vitamin B12 absorption. Elderly patients taking H2 receptor antagonists are more likely to require B12 supplementation than those not taking such drugs. H2 blockers may also reduce the absorption of drugs (azole antifungals, calcium carbonate) that require an acidic stomach. In addition, multiple studies suggest the use of H2 receptor antagonists such as ranitidine may increase the risk of infectious diarrhoea, including traveller's diarrhoea and salmonellosis. A 2005 study found that by suppressing acid-mediated breakdown of proteins, ranitidine may lead to an elevated risk of developing food or drug allergies, due to undigested proteins then passing into the GI tract, where sensitisation occurs. Patients who take these agents develop higher levels of immunoglobulin E against food, whether they