Ranitidine

Ranitidine, also known by the brand name Zantac, is a drug that lowers stomach acid production. It treats conditions like peptic ulcers, gastroesophageal reflux disease, and Zollinger–Ellison syndrome. It can be taken orally, injected into a muscle, or injected into a vein. The World Health Organization includes it on its List of Essential Medicines.

In September 2019, a probable carcinogen called N-nitrosodimethylamine (NDMA) was found in ranitidine products from several manufacturers, leading to recalls. By April 2020, the drug was pulled from the U.S. market and suspended in the European Union and Australia because of these concerns. A reformulated version was approved in Australia in October 2024 and in the United States in November 2025.

Common side effects include headaches and, for injections, pain or a burning sensation at the site. Serious side effects can include cancer, liver problems, a slow heart rate, pneumonia, and the risk of masking stomach cancer. It is also linked to a higher chance of *Clostridioides difficile* colitis. Ranitidine works as an H2 histamine receptor antagonist, blocking histamine and thereby reducing the amount of acid released by stomach cells.

First discovered in England in 1976, ranitidine entered commercial use in 1981.

**Medical uses:** It relieves heartburn and is used for short-term and maintenance therapy of gastric and duodenal ulcers. When taken with nonsteroidal anti-inflammatory drugs (NSAIDs), it lowers the risk of ulceration, though proton-pump inhibitors (PPIs) are more effective for preventing NSAID-induced ulcers. It treats pathologic gastrointestinal hypersecretory conditions like Zollinger–Ellison syndrome, gastroesophageal reflux disease (GERD), and erosive esophagitis. It is part of a multidrug regimen for *Helicobacter pylori* eradication to reduce duodenal ulcer recurrence, and it is used for recurrent postoperative ulcers and upper GI bleeding. Preoperatively, it prevents acid-aspiration pneumonitis by raising gastric pH without generally affecting gastric volume; a 2009 meta-analysis found it more effective than PPIs at reducing gastric secretion volume before anesthesia. It may also have an anti-emetic effect when given before surgery. In critically ill patients, it prevents stress-induced ulcers. Along with diphenhydramine, it serves as a secondary treatment for anaphylaxis after first-line epinephrine.

**Adverse effects:** Clinical trials have reported various events. Central nervous system effects include rare reports of malaise, dizziness, somnolence, insomnia, and vertigo; in severely ill or elderly patients, reversible mental confusion, agitation, depression, and hallucinations have occurred. Cardiovascular issues such as arrhythmias—tachycardia, bradycardia, atrioventricular block, and premature ventricular beats—have been noted. Gastrointestinal effects: H2 blockers can cause vitamin B12 deficiency by reducing absorption of food-bound B12, especially in elderly patients who may need supplementation. They may also reduce absorption of drugs requiring an acidic stomach (e.g., azole antifungals, calcium carbonate). Studies suggest an increased risk of infectious diarrhea, including traveler’s diarrhea and salmonellosis. A 2005 study indicated that suppressing acid-mediated protein breakdown may raise the risk of food or drug allergies, as undigested proteins pass into the GI tract and trigger sensitization; patients developed higher immunoglobulin E levels against food, and even months after stopping the drug, elevated IgE persisted in 6% of patients. Liver effects: cholestatic hepatitis, liver failure, hepatitis, and jaundice require immediate discontinuation; blood tests may show elevated liver enzymes or eosinophilia, and severe cases may need a liver biopsy. Lung effects: H2 antagonists may increase pneumonia risk in hospitalized patients, and ranitidine raises the risk of community-acquired pneumonia in both adults and children. Blood effects: thrombocytopenia is rare but known, usually appearing after weeks or months, though it can occur within 12 hours in sensitized individuals; platelet counts typically drop to 80% of normal, and it may be linked to neutropenia and anemia. Skin effects: rash, rare cases of erythema multiforme, hair loss, and vasculitis have been seen.

**Precautions:** Symptom relief from ranitidine does not rule out gastric malignancy. It must be used cautiously in people with kidney or liver impairment and avoided in those with porphyria, as it may trigger an attack. In children, gastric acid inhibitors are linked to a higher risk of acute gastroenteritis and community-acquired pneumonia. A cohort analysis of over 11,000 neonates found an association between H2 blocker use and increased incidence of necrotizing enterocolitis in very-low-birth-weight infants, along with about a six-fold increase in mortality, necrotizing enterocolitis, and infections such as sepsis, pneumonia, and urinary tract infection.