FDA says stomach acid drugs can lower magnesium

WASHINGTON (Reuters) - Prescription ulcer drugs such as AstraZeneca Plc's blockbuster, Nexium, will carry a new warning that long-term use may cause low magnesium levels, U.S. health officials said on Wednesday.

Low magnesium can lead to complications such as muscle spasms, irregular heartbeat and seizures. Patients may need to stop taking the drugs if magnesium supplements do not help, the Food and Drug Administration said.

The medicines, called proton pump inhibitors, are widely used for treating ulcers, acid reflux and other conditions. About 21 million U.S. patients filled prescriptions for the drugs in 2009, the FDA said.

Sales of Nexium, the market leader, topped $5 billion in 2010, but are expected to fall with generic competition. Cheaper copies already are sold in Europe and should hit the large U.S. market in 2014.

Other proton pump inhibitors sold by prescription include Takeda Pharmaceutical Co Ltd's Dexilant and Prevacid, AstraZeneca Plc's Prilosec and Vimovo, Santarus Inc's Zegerid, Pfizer Inc's Protonix and Johnson & Johnson and Eisai Co Ltd's Aciphex. Generic versions of Prevacid, Protonix and Prilosec also are available.

Most low-magnesium cases reviewed by regulators occurred after one year of use but some were as early as three months. In one-quarter of roughly four dozen cases, magnesium supplements did not help and the patients had to stop taking the medicine, the FDA said.

Average use of prescription forms of the drugs is about six months.

The FDA said there was little risk of low magnesium with lower-dose over-the-counter ulcer medicines if they are taken short term as directed. Prilosec, Zegerid and Prevacid are sold in nonprescription forms.

Officials at the drugmakers had no immediate comment or could not immediately be reached.

Details were released on the FDA website here