New research suggests that medicine made from cannabis may dramatically reduce seizures in people with certain severe types of epilepsy.

In two separate clinical trials, researchers tested a purified solution of cannabidiol (CBD), a compound found in cannabis that does not produce a high.

One study involved 120 children with a rare form of the neurological disease called Dravet syndrome that had caused them to have at least four seizures in the past month. They were randomly assigned to take either the CBD or a placebo two times a day and, after 14 weeks, the kids in the CBD group experienced a 39 percent reduction in the frequency of their seizures compared with a 13 percent average reduction in the placebo group.

The second study involved 171 patients, bot children and adults, who have a type of epilepsy called Lennox-Gastaut syndrome. To qualify, participants had to average at least two “drop seizures” – meaning they went limp and fell to the ground – a week. They also took either CBD or a placebo for 14 weeks, and those in the CBD control group experienced a 44 percent drop in the frequency of drop seizure versus an average reduction of 22 percent in the placebo group.

The CBD medicine, called Epidiolex, “is not a silver bullet, but there are children who benefit from this more than they have from other treatments,” said Dr. Elizabeth Thiele, the trial supervisor and director of the Pediatric Epilepsy Program at Massachusetts General Hospital.

Patients in both studies had previously tried several other anti-epilepsy drugs which hadn’t helped. During the studies, they continued taking any other drugs they were already on — an average of three anti-epilepsy drugs — along with the CBD or placebo treatment.

Epidiolex, manufactured by UK-based GW Pharmaceuticals, hasn’t been approved yet by the U.S. Food and Drug Administration and is not yet available for sale, even in states where medical marijuana has been legalized. The studies were presented this week at the American Epilepsy Society Annual Meeting in Texas.