• The primary endpoint is the mean pain due to MS NRS score measured at the end of treatment (week 14). [ Time Frame: 14 weeks ] [ Designated as safety issue: No ]
• The Numerical Rating Scale (NRS) measure of pain intensity has been selected as the primary efficacy endpoint. Unidimensional pain scales such as the 11-point NRS have been used extensively and validated for somatic and neuropathic pain [ Time Frame: 14 weeks ] [ Designated as safety issue: No ]

• The primary endpoint is the mean pain due to MS NRS score measured at the end of treatment (week 14).
• The Numerical Rating Scale (NRS) measure of pain intensity has been selected as the primary efficacy endpoint. Unidimensional pain scales such as the 11-point NRS have been used extensively and validated for somatic and neuropathic pain

• Proportion of subjects showing a 30% or more and 50% or more improvement in their primary endpoint scores between baseline and end of treatment [ Time Frame: 14 weeks ] [ Designated as safety issue: No ]
• Change in pain from baseline to end of the treatment using the NPS (Neuropathic Pain Scale) [ Time Frame: 14 weeks ] [ Designated as safety issue: No ]
• Break-through analgesia usage [ Time Frame: 14 weeks ] [ Designated as safety issue: No ]
• BPI (Brief Pain Inventory) short form [ Time Frame: 14 weeks ] [ Designated as safety issue: No ]
• SGIC (Subject Global Impression of Change) [ Time Frame: 14 weeks ] [ Designated as safety issue: No ]
• Sleep Quality [ Time Frame: 14 weeks ] [ Designated as safety issue: No ]

• proportion of subjects showing a 30% or more and 50% or more improvement in their primary endpoint scores between baseline and end of treatment
• change in pain from baseline to end of the treatment using the NPS (Neuropathic Pain Scale)
• Break-through analgesia usage
• BPI (Brief Pain Inventory) short form
• SGIC (Subject Global Impression of Change)
• Sleep Quality

The purpose of this study is to find out if cannabis-based medicine compared to a dummy medicine (placebo that contains no active ingredient) can help the central neuropathic pain patients experience as a result of multiple sclerosis. This type of pain "central neuropathic pain" is described as shooting, stabbing, burning or searing like sensation, which is often worse at night.

GW has shown in phase II and III studies that Sativex has analgesic properties that are effective in relieving neuropathic pain. These studies suggested that Sativex is well tolerated and may also improve sleep and quality of life. GW is conducting this study to further demonstrate these effects.

• Drug: Sativex
• Drug: Placebo

Inclusion Criteria:

• Any disease sub-type of MS of at least two years duration
• Central neuropathic pain (CNP) of at least three months and expected to remain stable for the study duration
• Moderate CNP defined by NRS pain score at baseline sum to at least 24
• Subject established on or previously tried and failed analgesic therapy for CNP
• If receiving disease modifying medications, stable dose for 3 months and maintained for study duration

Exclusion Criteria:

• Subjects whose identified pain is likely to be nociceptive, musculoskeletal (including spasms) peripheral neuropathic or psychogenic in origin, or due to trigeminal neuralgia.
• Other non central neuropathic pain of a severity which is likely to interfere with the patients assessment of CNP
• medical history suggests subject is likely to relapse/remit during course of study
• history of schizophrenia (including family history), other psychotic illness, severe personality disorder or other significant psychiatric disorder other than depression associated with MS
• known or suspected history of alcohol abuse, epilepsy or recurrent seizures or hypersensitivity to cannabinoids
• travel outside of the country of residence planned during the study
• significant cardiac, renal or hepatic impairment
• subjects with current recreational cannabis, medicinal cannabis or synthetic cannabinoid based medications within 3 months prior to study entry and unwilling to abstain for the duration of the study