Generic-drug utilization exeeds 60 percent in Medicare Part D. The high generic dispensing rate in Medicare Part D is helping to keep Part D premiums and program costs lower than originally forecast. In recent months, numerous studies have shown the important role that increased use of generic drugs can play in lowering health care costs. In addition, competition from generic alternatives helped contribute to prescription drug-spending growth rate in 2005 slowing to its lowest growth rate in over a decade, rising just 5.8 percent.