Epidiolex is a prescription medication used to treat seizures caused by three specific conditions: Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex. It is approved for patients one year of age and older, making it one of the few options available for very young children with these severe forms of epilepsy. The active ingredient is cannabidiol (CBD), a compound derived from the cannabis plant, but unlike marijuana or recreational CBD products, Epidiolex is a pharmaceutical-grade formulation that has gone through rigorous clinical testing.
The Three Conditions Epidiolex Treats
All three conditions Epidiolex targets involve drug-resistant seizures, meaning patients have already tried other medications without adequate relief. These are not mild or occasional seizures. They are frequent, often debilitating, and in many cases begin in infancy or early childhood.
Lennox-Gastaut syndrome (LGS) typically appears between ages 3 and 5 and causes multiple types of seizures, including “drop seizures” where a person suddenly loses muscle tone and falls. These can happen dozens of times a day and carry a high risk of injury. LGS also affects cognitive development over time.
Dravet syndrome begins in the first year of life and is one of the most severe childhood epilepsies. Seizures are prolonged, frequently triggered by fever, and resistant to most standard treatments. Children with Dravet syndrome often experience developmental delays and have an elevated risk of sudden unexpected death in epilepsy.
Tuberous sclerosis complex (TSC) is a genetic condition that causes noncancerous growths in the brain and other organs. The brain growths disrupt normal electrical activity, leading to seizures in roughly 85% of people with TSC. These seizures often start in infancy and can be difficult to control.
How Well It Works
Epidiolex doesn’t eliminate seizures entirely for most patients, but it can significantly reduce how often they occur. In clinical trials for Lennox-Gastaut syndrome, patients experienced a 48% to 71% median reduction in drop seizure frequency within 28 days. That kind of decrease can be life-changing for someone who was falling multiple times a day.
For tuberous sclerosis complex, a randomized trial of 224 patients found that those taking Epidiolex saw roughly a 49% reduction in their primary seizure type over 16 weeks, compared to 27% for those on a placebo. Notably, the lower dose (25 mg/kg per day) worked just as well as the higher dose (50 mg/kg per day) while causing fewer side effects.
Epidiolex is always used alongside other seizure medications, not as a standalone treatment. It’s added when existing drugs aren’t doing enough on their own.
How CBD Differs From Standard Seizure Drugs
Despite being derived from cannabis, Epidiolex does not work through the body’s cannabinoid receptors, the same receptors that THC activates to produce a high. The exact way it reduces seizures is still not fully understood, which is unusual for an FDA-approved drug but not unheard of in epilepsy treatment. Several older seizure medications also have mechanisms that aren’t completely mapped out. What matters clinically is that the effect has been demonstrated in controlled trials.
Epidiolex contains no THC and does not cause intoxication. It was initially placed in Schedule V of the Controlled Substances Act in 2018, the least restrictive category, and has since been descheduled at the federal level.
What to Expect During Treatment
Epidiolex comes as a liquid taken by mouth. The dose is based on body weight, starting low and gradually increasing over several weeks. Most patients begin at 5 mg per kilogram of body weight per day, split into two doses. After one week, this is typically doubled to 10 mg/kg per day. If seizures aren’t adequately controlled at that level, the dose can continue to increase in weekly steps up to a maximum of 20 mg/kg per day.
This slow titration helps minimize side effects and gives the care team time to monitor how your body responds. Bloodwork to check liver function is required before starting treatment, then at 1 month, 3 months, and 6 months. Additional blood tests are needed whenever the dose changes or when other medications that affect the liver are added or adjusted.
Side Effects and Liver Monitoring
The most commonly reported side effects in clinical trials include sleepiness, decreased appetite, diarrhea, fatigue, and sleep disturbances. For many patients, these effects are mild and tend to lessen over time as the body adjusts.
Sleepiness is particularly common in people who also take clobazam, one of the drugs frequently prescribed alongside Epidiolex for Lennox-Gastaut syndrome. This happens because Epidiolex slows the breakdown of clobazam in the body, effectively raising its levels in the blood. If excessive drowsiness becomes an issue, your doctor may lower the clobazam dose rather than discontinuing Epidiolex.
The most serious concern is liver injury. Epidiolex can cause elevations in liver enzymes, which is why regular blood monitoring is built into the treatment plan. The risk is higher in patients who also take valproate, another common epilepsy medication, and in those on higher doses. Symptoms to watch for include nausea, vomiting, abdominal pain, dark urine, or yellowing of the skin. Liver enzyme elevations are typically reversible when caught early through routine testing.
Interactions With Other Seizure Medications
Because Epidiolex is always used in combination with other drugs, interactions matter. Beyond clobazam, it can modestly raise blood levels of several other seizure medications, including rufinamide, topiramate, zonisamide, and eslicarbazepine. In studies, these increases were generally small (ranging from about 9% to 24%) and stayed within normal therapeutic ranges, meaning they didn’t cause additional problems for most patients.
Still, the combination effects are one reason why close follow-up is important during the first several months of treatment. Your care team will likely check blood levels of your other medications and adjust doses as needed to find the right balance.