Lansoprazole, sold under the brand name Prevacid among others, is a medication which reduces stomach acid.

[4][3] Serious side effects may include osteoporosis, low blood magnesium, Clostridioides difficile infection, and pneumonia.

Lansoprazole's plasma elimination half-life (1.5 h) is not proportional to the duration of the drug's effects to the person (i.e., gastric acid suppression).

[22] Patent protection of the lansoprazole molecule expired on 10 November 2009,[23][24] and generic formulations became available under many brand names in many countries.

[31] As of 2015[update] laboratory studies were underway on analogs of lansoprazole to explore their use as potential PET imaging agents for diagnosing tauopathies including Alzheimer's disease.