Diastat (diazepam rectal gel) is a rescue medicine that is used in emergency situations to stop acute repetitive seizures. It is marketed by Bausch Health, formerly known as Valeant Pharmaceuticals.
The medicine is approved by the U. S. Food and Drug Administration (FDA) for the treatment of refractory seizures. In Dravet syndrome patients, it is commonly used to quickly stop a seizure before it progresses to status epilepticus. Diastat is not intended to replace daily anticonvulsants.
How Diastat works
The active component of Diastat, diazepam, is a GABA agonist, a molecule that acts similar to GABA. GABA is a signaling molecule that inhibits the activity of nerve cells. It does so by binding to GABA receptors. Diazepam binds to one class of GABA receptors called GABAA receptors and mimics GABA’s action.
The majority of Dravet syndrome patients carry a mutation in the SCN1A gene, which provides instructions to build a subunit of sodium channels called NaV1.1. Brain cells communicate with each other through electric signals, and sodium channels are essential for signal transduction. The SCN1A mutation is thought to affect mainly GABA-releasing neurons, which leads to irregular signaling in the brain and seizures.
Diazepam is thought to decrease seizure frequency in Dravet syndrome patients by compensating for the impaired activity of GABA-releasing neurons.
Diastat in clinical trials
The effectiveness and safety of Diastat have not been tested in patients with Dravet syndrome and children younger than two. Two randomized, double-blind, placebo-controlled clinical trials showed, however, that Diastat can efficiently control acute repetitive seizures.
In the first trial, 91 participants (47 children and 44 adults) with a history of acute repetitive seizures were selected randomly to receive either Diastat or an identical-looking placebo. Doses ranged from 0.2 mg per kilogram (kg) of body weight, to 0.5 mg per kg, depending on the age of the patient. The first dose was given at the onset of a seizure episode. Children were treated again four hours after the first dose and were observed for 12 hours. Adults received the second dose four hours, and a third dose 12 hours after the first dose and were observed for 24 hours. The frequency of seizures was significantly lower in children and adults receiving Diastat compared to patients receiving placebo. The time to the first seizure recurrence also was significantly longer in the Diastat group than in the placebo group.
In the second trial, 114 epilepsy patients were selected randomly to receive either Diastat or a placebo. Diastat was given at a dose of between 0.2 mg per kg and 0.5 mg per kg, depending on the age of the patient. At the onset of an acute repetitive seizure episode, participants received a single dose of Diastat or a placebo. They were observed for 12 hours. During this period, patients in the Diastat group experienced no seizures; the placebo group experienced a median of two seizures. There also were more seizure-free patients in the Diastat group (55 percent) than in the placebo group (34 percent). The difference of both parameters was statistically significant.
Additional information
Rectal administration of Diastat requires the removal of clothing, which can be socially embarrassing when used outside of the home. A diazepam nasal spray is in development, and a Phase 1 clinical trial (NCT02724423) at the Washington University School of Medicine in Missouri is currently recruiting epilepsy patients.
Patients who use Diastat on a regular basis can develop resistance to the medication. It is recommended to use Diastat only in an emergency to prevent resistance.
Common side effects of Diastat include dizziness, headache, stomach pain, lack of coordination, and drowsiness.
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