Popular anti-heartburn drugs such as proton-pump inhibitors that block stomach acid production heighten the risk of an increasingly common infectious form of diarrhea, researchers said on Monday.

Taking such drugs as AstraZeneca’s Nexium and Losec or their generic versions tripled the risk of diarrhea blamed on the Clostridium difficile bacteria, the study concluded.

Frequently prescribed anti-heartburn drugs called H2 antagonists that include GlaxoSmithKline’s Zantac were found to double the risk of the bacterial diarrhea, the report said.

The drugs reduce gastric acid, opening the way for the bacteria to multiply in the digestive system.

Clostridium is the third-most common type of infectious diarrhea in patients aged 75 and older, study author Sandra Dial of McGill University, Montreal, wrote in this week’s issue of the Journal of the American Medical Association.

Exposure to Clostridium difficile bacteria, which causes infection and inflammation of the intestine, previously occurred mostly during hospital stays, but cases have increasingly been contracted in community settings, the study said. The number of community-acquired cases rose to 22 per 100,000 people in 2004 from 1 in 100,000 a decade earlier, it said.

Recent outbreaks in the United States and in the Canadian province of Quebec indicate strains of the bacteria may be increasingly deadly, according to previous research.

While antibiotics formerly blamed for outbreaks of the illness have declined in use, the acid-blocking drugs have become steadily more popular to treat ulcers and conditions such as gastric reflux disease, the report said.

SOURCE: Journal of the American Medical Association