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Older Heart Failure Patients Receive Improper Diabetes Drug

Krysten Modrzejewski

A new study shows that Medicare patients with heart failure and diabetes mellitus commonly leave the hospital with a prescription for an antidiabetes agent that could seriously worsen their health.

Product labeling for metformin and the class of antidiabetic agents known as thiazolidinediones advises against the use of these drugs in patients with certain types of heart failure. Metformin increases the risk of life-threatening lactic acidosis in patients whose heart failure requires drug treatment, and thiazolidinediones---such as pioglitazone and rosiglitazone---increase patients' fluid volume, which can exacerbate heart failure in patients whose disease is already moderate to severe.

A medical record review of two samples of over 25,000 Medicare patients was performed. The records of patients with a primary diagnosis of heart failure and a concurrent diagnosis of diabetes were collected. Metformin or thiazolidinedione use in this subset of patients was determined by a prescription for either agent at hospital discharge.

In the first data sample, collected from April 1998 to March 1999, 7.1% of patients were discharged with a prescription for metformin, and 7.2% had a prescription for a thiazolidinedione. Of those patients discharged with a metformin prescription, 88% of the patients were taking the drug upon admission.

In the second data sample, collected from July 2000 to June 2001, 11.2% of patients were discharged with a metformin prescription, and 16.1% were discharged with a thiazolidinedione prescription. Similar to the first group, 87% of the patients discharged with a metformin prescription were taking metformin on admission.

By 2001, one fourth of these Medicare patients, who had been in the hospital because of heart failure, were leaving the facility with a prescription for an antidiabetic agent that could aggravate their cardiac problem or increase their risk for a potentially fatal metabolic condition.

At discharge, 98% of the patients treated with metformin were already being treated with at least one drug commonly used to treat heart failure, which is contraindicated in the product labeling.

The findings, which were reported in the July 2, 2003, edition of Journal of the American Medical Association, confirm a trend that limited data have suggested.

Excluded from the study were patients without social security numbers, those on hemodialysis, transferred patients, patients who left against medical advice, patients younger than 65 years, and those who did not survive to discharge.

The authors cited the possible reasons why prescribing these agents in heart failure occurred. Some physicians may not aware of the risks, or they may believe glucose control is a benefit than is more important than the risk of lactic acidosis; alternatively, they may believe that these risks are overestimated.

The authors suggested the need for safe diabetic drug therapy, and further studies need to be done to determine what are the consequences of the current pattern of use with metformin and thiazolindiones in diabetic patients with moderate to severe heart failure.