The discontinuation rates because of adverse reactions in clinical trials were 5%, 6% and 19% for patients randomised to receive cenobamate at doses of 100 mg/day, 200 mg/day and 400 mg/day respectively, compared to 3% in patients randomised to receive placebo. The 400 mg dose was more associated with adverse reactions especially when taken concomitantly with clobazam.
The adverse reactions most commonly leading to discontinuation, in descending order of frequency, were: ataxia (1.6% vs 0.5% placebo), dizziness (1.6% vs 0.5% placebo), somnolence (1.4% vs 0.5% placebo), nystagmus (0.7% vs 0% placebo), vertigo (0.7% vs 0% placebo) and diplopia (0.5% vs 0% placebo). These adverse reactions are dose-dependent and the titration scheme should be strictly followed.
Tabulated list of adverse reactions: Adverse reactions reported in clinical studies are listed in Table 3 per system organ class (SOC) and per frequency. Within each frequency group, undesirable effects are ranked in decreasing order of severity: very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1,000 to <1/100) and rare (≥1/10,000 to <1/1,000). (See Table 3.)

Description of selected adverse reactions: Drug reaction with eosinophilia and systemic symptoms (DRESS): Three cases of DRESS were reported within 2 to 4 weeks of starting cenobamate in studies with high starting doses (50 mg or 100 mg once daily) and weekly or faster titration. When cenobamate was initiated at 12.5 mg/day and titrated every two weeks, in an open-label safety study of 1,340 epilepsy patients, no cases of DRESS were reported.
At the time of prescription, patients should be advised of the signs and symptoms of DRESS and monitored closely for skin reactions. Symptoms of DRESS include typically, although not exclusively, fever, rash associated with other organ system involvement, lymphadenopathy, liver function tests abnormalities and eosinophilia. It is important to note that early manifestations of hypersensitivity, such as fever or lymphadenopathy, may be present even though rash is not evident. If signs and symptoms suggestive of these reactions appear, cenobamate should be withdrawn immediately and an alternative treatment considered (as appropriate). XCOPRI should always be initiated at 12.5 mg once daily and titrated not faster than once every two weeks (see Dosage & Administration and Precautions).
Hypersensitivity: Four (0.9%) Cenobamate treated patients and one (0.5%) placebo patient experienced an event of hypersensitivity. Two patients in the cenobamate dose group experienced events of drug hypersensitivity. One cenobamate treated patient experienced an event of hypersensitivity and 1 cenobamate treated patient experienced an event on eyelid oedema. The placebo patient experienced an event of hypersensitivity. All events were classified as mild or moderate.
Elderly: Safety data from the Pooled Double-Blind and All Phase 2/3 datasets along with PK data from a Phase 1 study showed no additional safety risks in elderly subjects ≥65 years of age at study entry. Additional subgrouping by age for subjects who were ≥65 years of age during study participation showed similar results for adverse reactions in these 87 subjects as compared with the 51 subjects who were ≥65 years of age at study entry (see Dosage & Administration).
View ADR Reporting Link