A Study of the Safety and Effectiveness of Nabiximols (Sativex), for the Relief of Symptoms of Spasticity in Subjects, From Part B, With Multiple Sclerosis.

The purpose of this study is to determine the effective dose range and to demonstrate a non-effective dose range of Sativex compared with placebo in relieving symptoms of spasticity due to multiple sclerosis, in subjects identified as having a capacity to respond to Sativex. This multi-center study will be conducted in two parts. All participants enrolled into the trial will receive Sativex during one of two parts of the study, but they will not know which part.