The law that created the Medicare drug benefit, or Medicare Part D, mandates that Medicaid beneficiaries who were also eligible for Medicare ("dual eligibles") receive their drug coverage from the Medicare drug program rather than Medicaid. So, rather than be allowed dual eligibles to choose between two programs, when the new Medicare law went into effect, it shifted Medicare-eligible Medicaid beneficiaries into the new program. As it turns out, drug manufacturers benefited handsomely from the switch.