Ranitidine 150mg tablet on blister pack. Ranitidine is a H2-antagonist (H2-receptor antagonists) which helps to reduce the amount of acid in the stomach. It can help with the treatment of stomach and duodenal ulcers, reflex oesophagitis (acid in the gullet) and to treat irritation and ulceration of the stomach caused by non-steroidal anti-inflammatory drugs (NSAIDs). It works by blocking the action of histamine on parietal cells in the stomach.