Also check out Sativex:

Sativex approved: In April 2005, Health Canada, the drug regulatory agency for Canada , approved the use of the cannabis-derived drug Sativex® (GW Pharmaceuticals) to treat MS-related pain. The approval was based on a small, four-week clinical trial conducted in the United Kingdom in 66 people with MS, the results of which were published in 2005 (Rog DJ et al. Neurology 2005;65:812-819). Sativex contains extracts from the marijuana plant and is administered as a spray into the mouth. This drug is not approved in the United States. In response to a request by the Committee on Safety of Medicines, an advisory body to the Canadian regulatory authority, GW Pharmaceuticals is now conducting a clinical trial to evaluate Sativex as a treatment for spasticity.