Abstract: Two randomized controlled trials were included, with a total of 115 participants. One study compared clonazepam to carbamazepine as monotherapy for participants with newly diagnosed psychomotor epilepsy (a condition corresponding to what is now termed mesial temporal lobe epilepsy). One study (published as abstract) compared clonazepam to ethosuximide as monotherapy for children with absence seizures. Based on the available data and the details on methodology provided, we judged both studies as being at unclear or high risk of bias for the domains assessed. In the study comparing clonazepam to carbamazepine, no difference was found between the groups regarding the proportion of participants who were seizure-free at one month after randomization (risk ratio (RR) 1.97, 95% confidence interval (CI) 0.99 to 3.94; 30 participants; very low-certainty evidence), three months after randomization (RR 1.19, 95% CI 0.62 to 2.29; 26 participants; very low-certainty evidence), and six months after randomization (RR 0.50, 95% CI 0.09 to 2.73; 9 participants; very low-certainty evidence). No statistical difference was found between clonazepam and carbamazepine in terms of proportion of participants with TEAEs leading to discontinuation (RR 2.61, 95% CI 0.80 to 8.52; 36 participants; very low-certainty evidence) and in terms of dropouts/withdrawals due to side effects, lack of efficacy or other reasons (RR 1.56, 95% CI 0.61 to 4.02; 36 participants; very low certainty evidence). The study did not provide any information on our other prespecified outcomes of interest. The study comparing clonazepam to ethosuximide did not provide any data on efficacy. The proportion of dropouts/withdrawal was higher in the group receiving clonazepam compared to the group receiving ethosuximide (RR 3.63, 95% CI 1.12 to 11.74; 79 participants; very low-certainty evidence). No information on other outcomes of interest was provided in this study. There is only limited and very low-certainty evidence from randomized controlled trials on the efficacy and tolerability of clonazepam used in monotherapy for the treatment of epilepsy. No difference in efficacy and tolerability was found in a small trial comparing clonazepam to carbamazepine for the treatment of mesial temporal lobe epilepsy. Clonazepam was less well tolerated than ethosuximide in a trial of children with absence seizures, however no comparative data on efficacy were provided. There is currently insufficient evidence to support the use of clonazepam as monotherapy treatment for epilepsy.

Plain-language summary: We identified only two small trials comparing clonazepam with a different drug in two different epileptic syndromes, mesial temporal lobe epilepsy (the most common and well-defined focal epilepsy with seizures originating in the internal part of the temporal lobe of the brain) and absence seizures (generalized seizures causing lapses of awareness). In the study conducted in mesial temporal lobe epilepsy, clonazepam was compared to carbamazepine (an antiepileptic drug used to treat focal epilepsy). In the study on absence seizures, clonazepam was compared to ethosuximide (a medication used to treat absence seizures). We judged both studies as being of poor quality. The studies did not follow the participants for long enough, and the total of participants was too low to draw definite conclusions on the role of clonazepam used in monotherapy. Results on tolerability were not reported consistently across the studies. No differences were found between clonazepam and carbamazepine in the proportion of seizure-free participants; however, this does not mean that clonazepam and carbamazepine have the same efficacy, as the lack of difference can be due to the small number of people included. The study comparing clonazepam with ethosuximide provided no results on efficacy. No differences were found between the two medications in terms of tolerability. However, the proportion of people who dropped out or withdrew from the study due to side effects, lack of efficacy or other reasons was higher in the clonazepam group compared to the ethosuximide group. So far, the evidence on the efficacy and tolerability of clonazepam used as a single antiepileptic drug for the treatment of epilepsy is scarce and of very low certainty; hence insufficient to base decisions on its use in monotherapy.