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By Susan Heavey

WASHINGTON, May 22 (Reuters) - Cases of acute kidney failure and some deaths have been reported in patients using Novartis AG's <NOVN.VX> <NVS.N> iron overload drug Exjade, the U.S. Food and Drug Administration said on Tuesday.

The oral drug's effect on the kidneys has been an issue since 2005, when a U.S. advisory panel voiced concerns and cautioned there were not enough long-term data.

The new reports on Exjade, which removes excess iron from some organs in patients receiving blood transfusions, come from an agency database that collects reported complications after a drug hits the market.

Novartis and the FDA said the company has already included the warning information on the drug's label and has alerted doctors.

The agency also urged physicians to monitor at-risk patients, such as those who already have kidney problems as well as the elderly and those taking medications that can affect the kidneys.

In its alert, the FDA said most of the kidney failure patients who died already had other complications and their illness was advanced. It did not say how many cases were reported.

Patients using the drug reported various blood deficiencies known as cytopenia that in some cases also led to death, the FDA said in a statement.

"The relationship of these episodes to treatment with Exjade is uncertain," the agency said, adding that most patients already had disorders often linked to bone marrow failure.

Other complications, including blood vessel inflammation, hives and hypersensitivity, were also reported.

Novartis developed the once-a-day dissolving tablet as an alternative to its infused treatment Desferal, which is given for up 12 hours almost every day.

Patients with blood disorders such as anemia who regularly undergo blood transfusions can experience iron overload, a potentially fatal condition that can overwhelm the liver, heart and other vital organs.

In September 2005, an FDA advisory panel recommended the agency approve Exjade but said they were concerned about the lack of safety data, especially over time. The outside experts also questioned the drug's impact on the liver and urged more study.

The FDA approved the drug later that year, and Europe cleared it in August 2006.

Novartis spokesman John Gilardi defended use of Exjade despite the kidney risks.

"The diseases that we're treating here are fatal if they're not treated. You have a very sick patient group," he told Reuters. "This is not a new issue for Exjade."

Canadian health authorities have also issued a similar advisory, Gilardi added.

Shares of Switzerland's Novartis on the New York Stock Exchange briefly fell more than 1 percent after the FDA alert before recovering. They were up 10 cents at $55.57 in late afternoon trade. The stock fell 1.8 percent in Europe.

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