Pepcid (famotidine) works through a targeted mechanism that provides effective acid reduction while maintaining some normal stomach function, making it particularly suitable for children. The medication specifically blocks histamine H2 receptors on the acid-producing cells (parietal cells) in the stomach lining. To understand this, imagine the stomach has millions of tiny acid pumps, and these pumps have different 'switches' that turn them on. One of the main switches is histamine, which normally tells the stomach to produce acid when food arrives. Pepcid works by blocking these histamine switches, preventing the signal from reaching the acid pumps. This reduces acid production by about 70-80%, which is enough to relieve symptoms and allow healing while still maintaining some acid for normal digestion. Unlike proton pump inhibitors that completely shut down acid production, Pepcid's more moderate approach preserves some stomach acid, which is important for digesting proteins, absorbing certain nutrients like iron and calcium, and protecting against some infections. The medication begins working within one hour of taking it, reaches peak effect in 1-3 hours, and continues working for 10-12 hours. This relatively long duration of action allows for convenient once or twice-daily dosing. Pepcid is highly selective for H2 receptors in the stomach and has minimal effects on other histamine receptors in the body, which is why it doesn't cause drowsiness like antihistamines that block H1 receptors. The drug undergoes minimal metabolism in the liver and is primarily eliminated unchanged by the kidneys, which explains why it has so few drug interactions compared to older H2 blockers like cimetidine.