Date-rape drugs may not be as prevalent as had been previously thought, according to new research.
Rohypnol is prescribed for people suffering from severe insomnia
But what are these substances and how do they affect those who are drugged?
Rohypnol has, for some time, been referred to as a date-rape drug.
It has been used by rapists to drug their victims prior to an attack.
Rohypnol - trade name for flunitrazepam - is a sedative which is used for the treatment of sleep disorders such as insomnia.
It is about 10 times stronger than Valium.
If combined with alcohol, the drug can increase the feeling of drunkenness and lower inhibitions. It can also lead to loss of memory.
It dissolves quickly and leaves no odour or taste, meaning it cannot be detected by potential victims.
The drug begins to take effect in about 30 minutes and lasts roughly eight hours.
Gamma-hydroxybutryate (GHB) is also reported to have been used to incapacitate rape victims.
The substance, which is thought to have first appeared in the mid 90s, is sometimes referred to as liquid ecstasy. It was made illegal in 2003.
As well as being known as a date-rape substance, it is also used by clubbers and some body-builders use it to aid muscle growth.
The substance can induce a "high" in small doses, but larger amounts produce an anaesthetic effect which can put people into a coma and even cause death.
It is potentially lethal when mixed with other substances - particularly alcohol.
The substance is usually sold as a salty tasting colourless liquid, which has no distinguishing smell.
Victims are often afraid of what will happen when they report the rape
Once consumed, a person's inhibitions are lowered, making the victim - or user - talkative and elated.
The Class C drug takes about 10 minutes to an hour to take effect and the symptoms can last up to a day.
It can also be bought as a powder and a pill and in extreme cases the drug has been injected.
In the past the Advisory Council on the Misuse of Drugs (ACMD) has said the drug - the possession of which carries a maximum penalty of two years imprisonment - was being "widely misused and has harmful effects".
One user described its effects to Plymouth University researchers: "(I) felt like I was drifting away in my own little bubble of consciousness, but my friends said I was puking and out of it."
In order to avoid being drugged, police advice people not to accept a drink from somebody they do not completely trust.
People are also advised not to share or exchange drinks or leave a drink unattended, even when visiting the toilet.