A new study by the University of Pittsburgh Graduate School of Public Health, which will appear in the August 23 issue of the Archives of Internal Medicine, has found that improved drug coverage under Medicare Part D has resulted in a spike in antibiotic use by seniors.

The study of more than 35,000 Medicare beneficiaries showed an encouraging increase in the use of antibiotics for pneumonia but also indicated an increase in costly, broad-spectrum and inappropriate antibiotic use. Use of brand-name drugs especially has increased.

“We found that the use of antibiotics increased in response to reductions in out-of-pocket price after Part D implementation,” the researchers wrote.

Researchers compared antibiotic use two years before and two years after the inception of Medicare Part D coverage, which reduced out-of-pocket drug costs by 13 and 23 percent. Antibiotic use increased the most among beneficiaries who did not have drug coverage prior to enrolling in Medicare Part D.