The study, which appears in Rheumatology, was small, brief, and likely the first of its kind, note the researchers. They write that the "encouraging" results warrant larger, longer studies.
The spray, called Sativex, is made by GW Pharmaceuticals, the British drug company that funded the study. It is sprayed into the mouth and the medication is absorbed under the tongue or the inside part of the cheek.
One of the researchers is GW Pharmaceuticals' medical director. Two others disclose having received honoraria from GW Pharmaceuticals.
First, patients rated their pain at rest, during movement, and first thing in the morning. They also rated their quality of sleep.
Next, the patients were given one of two sprays to use every evening for about a month. Sativex was one of those sprays. The other was an empty spray (placebo).
Sativex was given to 31 patients. The other 27 patients got the placebo. No one knew which patients had gotten Sativex.
Sativex contains THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol). Those are key therapeutic compounds in cannabis that have been shown by other studies to produce effects on pain and inflammation, write the researchers.
Compared with the placebo group, patients taking Sativex had notable improvements in pain (including pain during movement and pain at rest), sleep quality, and RA disease activity, the researchers report.
Morning pain didn't change much but was "surprisingly low" to begin with, write Blake and colleagues.
The sprays were only used in the evening to minimize any intoxication. The most common side effects with Sativex were dizziness (eight patients, or 26% of the Sativex group), dry mouth (four patients, or 13%), and lightheadedness (three patients, or 10% of those taking Sativex).