28 Pa. Code § 25.61 – General provisions.

(a) Persons maintaining stocks or having controlled substances in production areas or on hand for distribution shall provide effective controls and procedures to guard against theft and diversion of the substances.
(b) Physical security controls shall be commensurate with the schedules and quantity of controlled substances on hand and required for normal business operations. If a controlled substance is transferred to a different schedule or a noncontrolled substance is listed on a schedule, or the quantity of controlled substances on hand significantly increases, physical security controls shall be expanded and extended accordingly.
(c) Persons who receive or transfer substantial quantities of controlled substances shall employ security procedures to guard against losses in transit.

This section cited in 28 Pa. Code § 551.3 (relating to definitions); and 49 Pa. Code § 21.284a (relating to prescribing and dispensing drugs).