. The advantage of diacetylmorphine over morphine is that diacetylmorphine is more fat soluble and therefore more potent by injection, so smaller doses of it are needed for the same analgesic effect. Both of these factors are advantageous if giving high doses of opioids via the subcutaneous route, which is often necessary in palliative care . The medical use of diacetylmorphine, in common with other strong opioids such as morphine , fentanyl and oxycodone , is controlled in the UK by the Misuse of Drugs Act 1971 . In the UK, it is a class A controlled drug and as such is subject to guidelines surrounding its storage, administration and destruction. Possession of diamorphine without a prescription is an arrestable offence. When diamorphine is prescribed in a hospital or similar environment, its administration must be supervised by two people who must then complete and sign a controlled drugs register (CD register) detailing the patient's name, amount, time, date and route of administration. In the case of a physician administering diamorphine, then he/she may administer the drug alone, however the rule requiring two registered practitioners, such as a nurse , midwife or another physician to sign the CD register still applies. The use of a witness when administering diamorphine is to avoid the possibility of the drug being diverted onto the black market . Diacetylmorphine is also used as a maintenance drug to treat certain groups of addicts, normally long term chronic intravenous (IV) heroin users, and even in these situations