A report says California wasted at least $13 million last year through inefficiencies in the way it delivers drugs to prison inmates.

The report by David Shaw, the inspector general for the state corrections department, says many costly prescriptions are discarded because of poor inventory record-keeping. Others are lost when inmates are transferred or released from prison.

The report, released Thursday, comes as the federal receiver who oversees prison medical care tries to counter accusations that he is spending too much money.

The receiver, J. Clark Kelso, says he is making many of the improvements recommended in the report.

That includes using more generic drugs and tracking the delivery of prescriptions to inmates.