Ranitidine is a competitive, reversible antagonist of histamine at the H2-receptors of gastric parietal cells, leading to a marked reduction in gastric acid secretion, both basal and stimulated. It is a second-generation H2-receptor antagonist (H2RA) with greater potency and longer duration of action than cimetidine. The 25mg strength is primarily used in pediatric populations in India for the management of acid-related disorders. It is important to note that following global safety alerts regarding the presence of N-nitrosodimethylamine (NDMA), a probable human carcinogen, many regulatory authorities, including India's CDSCO, have suspended or restricted its use. However, specific formulations, particularly low-dose syrups for children, may still be available under strict regulatory oversight for short-term use where benefits outweigh risks.
Adult: Not typically used at 25mg strength in adults. Adult doses: 150mg twice daily or 300mg once daily.
Note: Oral: Can be taken with or without food. If taken for heartburn, take 30-60 minutes before eating food or drinking beverages that cause heartburn. Tablets can be swallowed whole with water. Dispersible tablets should be dissolved in a small amount of water. Syrup should be measured with the provided measuring cup/spoon.
Ranitidine competitively and reversibly inhibits the binding of histamine to the H2-receptors located on the basolateral membrane of gastric parietal cells. This blockade prevents the activation of adenylate cyclase, reducing intracellular cyclic AMP (cAMP) levels. The decrease in cAMP inhibits the activation of the proton pump (H+/K+ ATPase), leading to a profound reduction in both the volume and hydrogen ion concentration of gastric juice. It suppresses basal, nocturnal, and food-stimulated acid secretion.
Pregnancy: Category B: Animal studies have shown no risk, but adequate human studies are lacking. Use only if potential benefit justifies potential risk to the fetus.
Driving: May cause dizziness, drowsiness, or blurred vision. Patients should not drive or operate machinery if affected.
| Warfarin | Ranitidine may alter warfarin absorption or metabolism; monitor INR closely. | Moderate |
| Midazolam, Triazolam | Ranitidine may increase bioavailability of these benzodiazepines, potentiating sedation. | Moderate |
| Ketoconazole, Itraconazole, Atazanavir | Reduced gastric acid may decrease absorption of these acid-dependent drugs. Administer with an acidic beverage or separate dosing. | Moderate |
| Procainamide | Ranitidine may reduce renal clearance of procainamide, increasing its levels and risk of toxicity. | Moderate |
| Glipizide, Glyburide | Ranitidine may potentiate hypoglycemic effect; monitor blood glucose. | Minor |
| Fentanyl | Case reports of delayed respiratory depression; monitor closely. | Moderate |
Same composition (Ranitidine (25mg)), different brands: