Controlled Drug
The United Kingdom Misuse of Drugs Act 1971 aimed to control the possession and supply of numerous listed drugs and drug-like substances.  The act allowed and regulated the use of some Controlled Drugs (designated CD) by various classes of persons (e.g. doctors) acting in their professional capacity.
In clinical practice, this mostly applies to the use of strong opiates for pain management and some amphetamine-like stimulants used for Attention-deficit hyperactivity disorder; both of which are regulated under Schedule 2.
The Royal Pharmaceutical Society of Great Britain maintains a live database that allows you to check the Legal Classification of Medicines.

# Schedules
Special responsibilities are placed upon pharmaceutical wholesalers, pharmacies and doctors in the stocking, distribution, issuing of prescriptions, supply and disposal of items listed under the first three of the schedules.  The regulations have been further tightened since Dr Harold Shipman used diamorphine to murder hundreds of his patients during the late 20th century.

## Schedule 1 - CD Lic
Drugs which are not used medically, and thus their possession and supply is prohibited; e.g. cannabis and LSD

## Schedule 2 - CD
Substances subject to the full controlled drug requirements; e.g. diamorphine (heroin), pethidine, cocaine. Prescriptions have previously had to be written out by hand with full details of the form and strength of the preparation. The total quantity has to be written out in both words and figures.  It is an offence for a doctor to issue an incomplete prescription or for a pharmacist to dispense a controlled drug unless all the required details are given.
It is the prescriber's responsibility to minimise the risk of dependence or misuse by ensuring that such drugs are not started for a particular patient without good cause, that the dose is not increased to the point where dependency is more likely, and to avoid being an unwitting source of supply for addicts. The quantities of controlled drugs prescribed should match the likely needs of the patients until the next clinical review and prescription forms should be secured against theft.
The safe custody requirements ensures that pharmacists and doctors holding stock of controlled drugs must store them in securely fixed locked containers and maintain a written register.  Disposal of expired stock must be witnessed by a designated inspector (either a local drug-enforcement police officer or official from health authority).

## Schedule 3 - CD No Reg
Include drugs subject to the same prescription requirements as Schedule 2 drugs, but not the safe custody requirements, nor need to maintain registers; e.g. barbiturates and temazepam. Phenobarbitone is exempt from the requirement of prescriptions needing to be fully written out by hand, although the date must still be hand written, and temazepam is exempt from all prescription requirements (i.e. only restricted re wholesale distribution and storage requirements).

## Schedule 4
Controlled drug prescription requirements and safe custody requirements do not apply.  Included drugs are Benzodiazepines, other than temazepam and flunitrazepam, and androgenic and anabolic steroids.

## Schedule 5 - CD Inv
Includes items, which because of their strength are exempt from all requirements other than the need to retain invoices for two years.