Drugs taken by tens of millions of people for acid reflux may contribute to heart disease, according to a Houston study, the latest and most serious red flag yet raised about possible harmful effects from long-term use.
In mouse models and human cultures, Methodist Hospital researchers found that proton pump inhibitors, or PPIs, caused blood vessels to constrict, a development that could lead to a number of cardiovascular problems if continued for a prolonged period of time. Those problems include hypertension and a weakened heart.
"Our data shows that PPIs impair the ability of blood vessels to relax," said Dr. John Cooke, chair of Methodist's cardiovascular services and the study's principal investigator. "It's definitely concerning - patients taking proton pump inhibitors may want to talk to their doctor about switching to another drug to protect their stomachs."
Cooke called for further investigation to determine whether the drugs are dangerous. He said Methodist and Stanford University, its partner in the new study, have already launched follow-up research looking at the effect of proton pump inhibitors in both former patients and new patients on the drug.
Cooke said the study, online at the journal Circulation, explains previous observations that people on proton pump inhibitors are at risk for a second heart attack. He said the findings also suggest the drugs may cause cardiovascular problems in people who've not previously had heart issues.
Proton pump inhibitors, such as Prilosec, Prevacid and Nexium, are used to treat a wide range of stomach disorders, most notably gastroesophageal acid reflux, or severe heartburn. Available both over the counter and with a prescription, they are the third highest-selling class of drugs in the United States.
Cooke said they are great at reducing stomach acidity, but were never approved for long-term use.
The study adds to a host of concerns about proton pump inhibitors, already the subject of Food and Drug Administration warnings issued for associations with an increased risk of bone fractures and an infection, Clostridium difficile, particularly dangerous in elderly patients. Studies also have found they may reduce the absorption of important nutrients, vitamins and minerals, as well as medications, and that they may leave users at increased risk of developing pneumonia.
Though the FDA recommends proton pump inhibitors be taken for eight to 12 weeks, experts say they breed dependency. Some patients stay on them for life.
Proton pump inhibitors work by suppressing the movement of protons into the intestine, which reduces the amount of acid there and in the stomach. But Cooke's study found the drugs also cause an increase in a chemical that suppresses the production of nitric oxide, proven to relax and protect arteries and veins.
In tissue cultures, Methodist researchers found proton pump inhibitors led to a 25 percent increase in the chemical that suppresses nitric oxide production. In mice, they found the drugs reduced blood vessel relaxation by more than 30 percent.