Clobazam for patients with Lennox-Gastaut syndrome and epilepsy

Post hypoxic myoclonus: A tale of two minds

Post hypoxic myoclonus (PHM) is considered a poor prognostic sign and may influence decisions regarding withdrawal of treatment. PHM is generally categorized in literature as either acute or chronic (also commonly referred to as Lance-Adams Syndrome) based on the onset of myoclonus. However, it may be more accurate to differentiate between the various presentations of PHM based on the clinical characteristics and electroencephalogram (EEG) findings for prognostication. Here, we describe a case of a 33-year-old female who presented after a cardiopulmonary arrest. MRI of the brain and cervical spine on admission were unremarkable. Twelve hours later, she developed generalized, stimulus-sensitive myoclonus suggestive of acute PHM. Various medications were trialed, and her symptoms eventually improved on clonazepam. On day 14, she started having resting and intention myoclonus, and dysarthria, consistent with LAS. Several adjustments were again made to her regimen, and she was eventually switched from clonazepam to baclofen which improved her resting myoclonus. This case highlights that PHM can present differently and have a markedly different outcome. It is important to develop a better understanding of the various types of PHM so as to avoid premature withdrawal of care.

Experience in the use of clobazam in the treatment of Lennox-Gastaut syndrome

Clobazam is a 1,5-benzodiazepine used successfully worldwide since the 1970s as an anxiolytic and antiepileptic drug. Since its recent Food and Drug Administration (FDA) approval in the United States in 2011 as adjunctive treatment for Lennox-Gastaut syndrome, it has continued to show sustained efficacy and a better safety and tolerability profile compared with other benzodiazepines. The two randomized, controlled studies that led to the US FDA approval, as well as the follow-up multicenter, open-label study of clobazam, showed ≥50% seizure reduction for more than 50% of Lennox-Gastaut syndrome patients, while none of the other FDA-approved treatments for LGS have demonstrated efficacy rates better than 50%. Clobazam appears to have a safe profile and sustained effectiveness over the first 3 years of use in LGS and other epilepsy syndromes with intractable seizures, which makes it a viable long-term treatment option.

Clobazam therapeutic drug monitoring: a comprehensive review of the literature with proposals to improve future studies

BACKGROUND

Clobazam was recently approved for Lennox-Gastaut syndrome in the United States. There is no published review article focused on clobazam therapeutic drug monitoring (TDM) in English.

METHODS

More than 200 clobazam articles identified by a PubMed search were carefully reviewed for information on clobazam pharmacokinetics. Clobazam is mainly metabolized by a cytochrome P450 (CYP) isoenzyme, CYP3A4, to its active metabolite, N-desmethylclobazam. Then, N-desmethylclobazam is mainly metabolized by CYP2C19 unless the individual has no CYP2C19 activity [poor metabolizer (PM)].

RESULTS

Using a mechanistic approach to reinterpret the published findings of steady-state TDM and single-dosing pharmacokinetic studies, 4 different serum clobazam concentration ratios were studied. The available limited steady-state TDM data suggest that the serum N-desmethylclobazam/clobazam ratio can be useful for clinicians, including identifying CYP2C19 PMs (ratio >25 in the absence of inhibitors). There are 3 possible concentration/dose (C/D) ratios. The clobazam C/D ratio has the potential to measure the contribution of CYP3A4 activity to the clearance of clobazam from the body. The N-desmethylclobazam C/D ratio does not seem to be a good measure of clobazam clearance and should be substituted with the total (clobazam + N-desmethylclobazam) C/D ratio.

CONCLUSIONS

Future clobazam TDM studies need to use trough concentrations after steady state has been reached (>3 weeks in normal individuals and several months in CYP2C19 PMs). These future studies need to explore the potential of clobazam and total C/D ratios. Better studies on the relative potency of N-desmethylclobazam compared with the parent compound are needed to provide weighted total serum concentrations that correct for the possible lower N-desmethylclobazam pharmacodynamic activity. Standardization and more studies of C/D ratios from clobazam and other drugs can be helpful to move TDM forward.

Clobazam: a newly approved but well-established drug for the treatment of intractable epilepsy syndromes

Clobazam, a 1,5-benzodiazepine, was introduced in the 1970s as an anxiolytic and antiepileptic drug. Despite worldwide usage, it was only recently approved in the United States (seizures associated with Lennox-Gastaut syndrome). This article reviews historical and recent data to help practitioners better understand clobazam's clinical properties and usage. In many clinical trials, open-label studies, and retrospective reviews, clobazam was generally associated with ≥50% seizure reduction for more than half of Lennox-Gastaut syndrome patients, with approximately 10% achieving freedom from drop attacks. Efficacy is persistent, with little evidence for development of tolerance. Clobazam's safety profile appears to be similar to that of other benzodiazepines, but with substantially decreased sedation and increased psychomotor performance. Studies suggest clobazam acts through potentiation of gamma-aminobutyric acid type A receptors in a manner similar to other benzodiazepines. However, clobazam appears to display greater selectivity for receptors responsible for anticonvulsant activity than for those involved in sedation.