Sativex is derived from whole plant extracts of Cannabis sativa. It contains delta-9-tetrahydrocannabinol (THC), which acts as a partial agonist of cannabinoid CB1 and CB2 receptors, and cannabidiol (CBD), which acts as an indirect antagonist of cannabinoid agonists.1 Sativex reduces overactivity of nerves damaged by MS that would normally result in spasticity, by interacting with cannabinoid receptors that are involved in movement and postural control.2
A two-phase study assessed the efficacy of Sativex in patients with moderate to severe spasticity; the primary endpoint was patient-reported severity of spasticity-related symptoms over a 24-hour period on a ten-point Numeric Rating Scale (NRS), with 0 representing no spasticity and 10 representing worst possible spasticity.
In the initial four-week, single-blind therapeutic phase looking at 572 patients, Sativex reduced mean NRS score for spasticity by 3.01 points from a baseline of 6.91 points, with 48% of patients achieving a more than 20% improvement in mean score over this initial period.
Of the 272 patients who were classified as responders, 241 entered a further 12-week phase in which they were randomised to receive Sativex or placebo. A significantly reduced NRS score was seen in patients receiving Sativex compared with those on placebo (estimated treatment difference 0.84 points, p=0.0002).3
The most common adverse effects seen with Sativex are dizziness (which occurs mainly during the initial titration phase) and fatigue. Both are usually mild to moderate and transient; where the recommended titration schedule is followed the incidence of dizziness and fatigue is greatly reduced.1
Treatment with Sativex must be commenced and supervised by a specialist experienced in the management of spasticity associated with MS. The Home Office has issued an open general licence for Sativex meaning that it can be prescribed and dispensed on an FP10 or FP10(CD) form.
The prescription writing requirements are those of a Schedule 2 drug, in that the dose, form and total quantity must be included in both words and figures.
There is no requirement for pharmacists to keep records in the CD register but they are advised that Sativex should be stored in a locked refrigerator where possible, or in a refrigerator not visible to the public if this is not possible.
- Sativex Summary of Product Characteristics, June 2010.
- GW Pharmaceuticals. Cannabinoid Science: Cannabinoid Compounds. www.gwpharm.com/types-compounds.aspx [June 2010].
- Ambler Z et al. Poster presented at 25th Congress of the European Committee for the Treatment and Research in Multiple Sclerosis (ECTRIMS), Dusseldorf, Germany, September 2009; P844.