A filled DEA Form 222 must be kept by the:

The correct answer indicates that the purchaser must keep a filled DEA Form 222 for three years. This form is crucial in the process of ordering and transferring controlled substances, specifically Schedule I and II drugs. The requirement for the purchaser to retain the form for three years aligns with the regulatory standards set forth by the Drug Enforcement Administration (DEA).

This retention period is essential as it allows for appropriate auditing and record-keeping, ensuring accountability in the handling of controlled substances. The three-year timeframe provides a reasonable duration for legal and regulatory compliance checks, allowing for any required investigations or follow-ups by authorities. Keeping the records organized and accessible for this period supports the overall goal of maintaining a safe and regulated pharmaceutical environment.

In contrast, the other options reflect incorrect retention periods for various entities involved in the distribution and management of controlled substances, illustrating that different types of organizations might have different requirements based on regulations.