BAKERSFIELD, Calif. (KERO) — The Food and Drug Administration approved new guidelines for a controversial Alzheimer's drug.

The new guidelines state the drug is for patients with early to mid-stage Alzheimer's. Drug maker Biogen said the update was made to clarify the status of the patients involved in studies that led to the drug's approval.

The FDA says its ability to reduce clumps of plaque in the brain is likely to slow Dementia.

Biogen is required to conduct a follow-up study.