These drugs are the most powerful medications for reducing
stomach acid levels; in fact, they almost completely shut down
the stomach's ability to produce acid. (Their science
fiction–sounding name comes from the last stage of the acid-
secreting process, called the "proton pump.") Proton pump
inhibitors are used for ulcers as well as for the treatment of
moderate to severe esophageal reflux, commonly known as
heartburn. Drugs in this family include lansoprazole (Prevacid),
omeprazole (Prilosec), and others. St. John's Wort The herb St.
John's wort is known to interact with numerous drugs. There are
two potential harmful interactions between St. John's wort and
proton pump inhibitors. One study found that use of St. John's
wort greatly decreases levels of omeprazole in the body. This
would be expected to lead to markedly reduced efficacy. The
other potential risk is more theoretical. When taken to excess,
the herb St. John's wort can cause an increased risk of sunburn.
Some evidence hints that proton pump inhi