A cannabis-based drug has been approved to treat the symptoms of multiple sclerosis.
Sativex is thought to be the first drug to tackle the symptoms of spasticity – involuntary muscle stiffness and spasms – associated with the condition.
The mouth spray will be made available after being approved by the medicines regulator.
It is the first cannabinoid medicine derived from whole plant extracts of the cannabis sativa plant, and is only the second cannabinoid drug to be licensed by the Medicines and Healthcare products Regulatory Agency (MHRA).
Cannabis is a Class B drug, and using it for medicinal purposes remains illegal in the UK.
But doctors can prescribe Sativex to MS patients experiencing the spasms and cramping associated with spasticity.
MS charities welcomed the regulator's approval of the drug, which was developed by UK-based GW Pharmaceuticals.
Pam Macfarlane, chief executive of the MS Trust, described the launch as a milestone.
She said: "We have been aware for a long time, based on comments from people with MS, that cannabis-based medicines can significantly improve spasticity, which is a common, complex symptom of MS."