Measuring controlled drugs

Author: Tina Zaki
Category: Developing your team, medication, Medicines Management Processes, Pharmacy Information
Date: March 24, 2022

How to prevent unaccounted-for losses of controlled drugs

Harold Shipman, known as Britain’s most prolific serial killer, was successful in diverting a large quantity of controlled drugs (CDs) for his own criminal purposes. The subsequent enquiry against him highlighted major limitations in the information available to audit the prescribing and supply of controlled drugs. This resulted in a new legislative structure to manage drugs that have the potential to be misused, which included the recording of a running balance of stock.

Keeping an accurate record of the quantity of liquid controlled drugs may be challenging as loss of volume can occur by frequent measuring, further complicated by the overage of some liquids during manufacture.

Unaccounted-for losses of controlled drugs by type

During 2018/19, there were 2,899 unaccounted-for losses of controlled drugs in England reported on the reporting tool – an average of eight daily – with methadone recording the highest number of those (see graph below).

Unaccounted-for losses of controlled drugs by type of drug 2018/19 (CQC: The safer management of controlled drugs July 2019)

Carrying out regular balance checks of all Schedule 2 CDs is recommended to identify any discrepancies at the earliest opportunity. This is done by completing a routine visual check alongside a weekly full balance check. For liquid controlled drugs, most organisations accept a 5% overage of the total volume, but parameters may vary between different establishments. The overage can be calculated using the equation below.

If the overage is not within the allowed parameters, a report must be made via the Controlled Drug reporting website which explains the incident and actions implemented to prevent future discrepancies.


  1. Safer management of controlled drugs, The Government’s response to the Fourth Report of the Shipman Inquiry, December 2004
  2. The safer management of controlled drugs, Care Quality Commission: Annual update 2018
  3. NHS East of England Controlled Drug Newsletter, Issue 13, Spring 2019

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