The Use of Clobazam, Midazolam, and Nitrazepam in Epilepsy

Pharmacotherapy for Focal Seizures in Children and Adolescents

Focal-onset seizures are among the most common forms of seizures in children and adolescents and can be caused by a wide diversity of acquired or genetic etiologies. Despite the increasing array of antiseizure drugs available, treatment of focal-onset seizures in this population remains problematic, with as many as one-third of children having seizures refractory to medications. This review discusses contemporary concepts in focal seizure classification and pathophysiology and describes the antiseizure medications most commonly chosen for this age group. As antiseizure drug efficacy is comparable in children and adults, here we focus on pharmacokinetic aspects, drug-drug interactions, and side effect profiles. Finally, we provide some suggestions for choosing the optimal medication for the appropriate patient.

Clobazam as an adjunctive treatment for infantile spasms

Infantile spasms constitute a catastrophic epileptic condition. Seizures in approximately half of children with infantile spasms fail to improve with initial treatment attempts; at present, data regarding alternative treatments are limited. We assessed the efficacy of clobazam as an adjunctive therapy in patients whose seizures failed to respond to initial regimens of standard treatment for infantile spasms. All patients from Severance Children's Hospital who received clobazam as adjunctive therapy for infantile spasms were selected for the study. The efficacy of clobazam was evaluated by assessing the daily spasm frequency. Patients were categorized as complete responders if the spasms disappeared within 2 weeks of introducing clobazam, and the patients became spasm-free during weeks 3 and 4. Tolerability was gauged by analyzing adverse events and discontinuation rates. In all, 171 patients qualified for the analysis. Clobazam was introduced after the administration of 2.6 (median; interquartile range [IQR], 1.0-4.0) failed antiepileptic drugs (AEDs), at the age of 8.2 months (IQR, 6.0-10.0 months). After clobazam therapy was initiated, 38 (22.2%) patients became spasm-free for ≥2 weeks. Thirteen out of the 38 complete responders remained spasm-free until the last follow-up and did not require the administration of other AEDs. In 10 patients, the electroencephalogram (EEG) tracings were also within normal limits. These patients were successfully weaned off of all AEDs. Patients with conditions of unknown etiology, who had fewer prior exposures to AEDs, and had not received prior adrenocorticotropic hormone (ACTH)/steroids were more likely to have complete spasm control than the others. Adverse effects were minor, and only 6 of 101 (6%) patients who experienced adverse events had their treatments discontinued during the 3-month follow-up period. The most common adverse events observed were hypersalivation, sedation, and sleep disturbance. Thus, clobazam might be an effective and safe alternative therapeutic option in patients whose seizures failed to respond to initial regimens of standard treatment for infantile spasms. Further prospective studies on clobazam for infantile spasms, focusing on specific good response groups, dosing protocols, and long-term outcome are needed.

Long-term use of clobazam in Lennox-Gastaut syndrome: experience in a single tertiary epilepsy center

OBJECTIVE

Clobazam (CLB) is a 1,5-benzodiazepine, which is known to be effective for treating refractory partial epilepsy. We have evaluated the long-term efficacy and tolerability of CLB as an add-on therapy in patients with Lennox-Gastaut syndrome (LGS).

METHODS

Forty-six patients with LGS who had received CLB add-on therapy were enrolled in this study. We retrospectively reviewed their clinical characteristics, including type of seizures, use of CLB, efficacy, adverse events, and retention rate.

RESULTS

The mean±SD dose of CLB was 0.70±0.37 mg/kg per day (range, 0.16-1.60 mg/kg per day). After 1 month on CLB, 15 patients (32.6%) became seizure-free and 10 patients (21.7%) had 50% or greater seizure reduction. Response to CLB was not significantly associated with age, sex, or etiology (symptomatic or not). Five (10.8%) of 46 patients maintained seizure remission for more than 12 months. Tolerance developed in 48.0% of initial responders, and the 3-year retention rate by the Kaplan-Meier method was 76.6%. Seven patients (15.2%) reported adverse events, including somnolence and behavioral change, but only one discontinued CLB.

CONCLUSIONS

Clobazam add-on therapy was effective and very tolerable in patients with LGS.

Clobazam for patients with Lennox-Gastaut syndrome and epilepsy

Lennox-Gastaut syndrome (LGS) is a form of childhood epileptic encephalopathy that continues to be challenging to treat and manage. The available treatments have failed to provide good control for patients with this devastating epilepsy syndrome. Clobazam is a promising antiepileptic medication, given its effectiveness and relatively low rates of adverse effects. It has been studied and used in several countries for the treatment of refractory seizures, including those that occur with LGS. Clobazam (Onfi™; Lundbeck Inc., IL, USA) has been studied in the USA to demonstrate its efficacy and safety for the treatment of seizures associated with LGS, and Phase II and III trials have recently been completed. This article will explore the use of clobazam in the treatment of LGS and present the results of Phase II and III studies, along with an overall summary of the treatment of LGS, as well as the possible role of clobazam in a treatment algorithm. We based this article on the most relevant reports with the term 'clobazam' found through a Medline search (1966-2011).

Update on the Genetic Polymorphisms of Drug-Metabolizing Enzymes in Antiepileptic Drug Therapy

Genetic polymorphisms in the genes that encode drug-metabolizing enzymes are implicated in the inter-individual variability in the pharmacokinetics and pharmaco-dynamics of antiepileptic drugs (AEDs). However, the clinical impact of these polymorphisms on AED therapy still remains controversial. The defective alleles of cytochrome P450 (CYP) 2C9 and/or CYP2C19 could affect not only the pharmacokinetics, but also the pharmacodynamics of phenytoin therapy. CYP2C19 deficient genotypes were associated with the higher serum concentration of an active metabolite of clobazam, N-desmethylclobazam, and with the higher clinical efficacy of clobazam therapy than the other CYP2C19 genotypes. The defective alleles of CYP2C9 and/or CYP2C19 were also found to have clinically significant effects on the inter-individual variabilities in the population pharmacokinetics of phenobarbital, valproic acid and zonisamide. EPHX1 polymorphisms may be associated with the pharmacokinetics of carbamazepine and the risk of phenytoin-induced congenital malformations. Similarly, the UDP-glucuronosyltransferase 2B7 genotype may affect the pharmacokinetics of lamotrigine. Gluthatione S-transferase null genotypes are implicated in an increased risk of hepatotoxicity caused by carbamazepine and valproic acid. This article summarizes the state of research on the effects of mutations of drug-metabolizing enzymes on the pharmacokinetics and pharmacodynamics of AED therapies. Future directions for the dose-adjustment of AED are discussed.

Acute administration of benzodiazepines as part of treatment strategies for epilepsy

Ad-hoc administration of benzodiazepines (BZD) is well established in status epilepticus, but intermittent BZD use in the treatment of chronic epilepsy is little known beyond catamenial epilepsy. We aim to assess the use of acute drug administration (ADA) in the treatment of 24 patients with epilepsy (9 idiopathic generalized, 14 focal symptomatic/cryptogenic, 1 migraine-epilepsy) receiving ADA for (1) prevention of generalized tonic-clonic seizures (GTCS) after minor seizures, (2) prevention of seizures at perceived risk, (3) prevention of seizure clusters. Standard ADA was 10 mg oral clobazam (CLB); one patient received 10 mg rectal diazepam. Concomitant antiepileptic drugs (AED) remained unchanged whenever possible. Ten patients used ADA always correctly, 7 mostly, 7 sporadically or not. Outcome considering seizure control was positive in 44% of all patients (59% of those who actually used ADA): 5 patients seizure free, 1 free of disabling seizures, 4 with >50% reduction in seizure frequency. Eleven had minor or no improvement, 3 patients could not be rated. Thirteen (of 19 possible) patients attempted prevention of seizures or clusters, 10 with full or >50% success (52.6 resp. 76.9%). Prevention of clusters sometimes required higher or repetitive CLB dosing. Self rating of patients who did use ADA was positive or very positive in 88.2%. Retention rate was 66.7% of all patients, and 88.2% of those using ADA. The best results were obtained in idiopathic generalized epilepsy (IGE) patients with seizures habitually triggered by typical factors (sleep deprival, alcohol) but also some others were successful. The only adverse effect was gait ataxia in a multiple-handicapped patient. ADA is an elegant and often successful but underused treatment option for selected patient groups where it can make the difference between becoming seizure free or not. Depending on the individual case it can be applied as monotherapy or in combination with a basis AED. A controlled investigation should follow.

Antiseizure activity of novel gamma-aminobutyric acid (A) receptor subtype-selective benzodiazepine analogues in mice and rat models

The antiseizure activity of benzodiazepines (BDZs) 1-5 in mice and rats as animal models is described. These BDZs have selective efficacy for alpha2beta3gamma2 and alpha3beta3gamma2 GABA(A)-receptors. Significant anticonvulsant activity with little or no motor impairment and therapeutic indexes (TI) of 2.8-44 (mice, ip) were observed for compounds 2-4 in the subcutaneous metrazole seizure (scMET) test. In rats, orally (po) the TI was >5 to 105. These compounds represent novel leads in the search for anticonvulsants devoid of sedative, ataxic, and amnestic side effects.

Benzodiazepines in epilepsy: pharmacology and pharmacokinetics

Benzodiazepines (BZDs) remain important agents in the management of epilepsy. They are drugs of first choice for status epilepticus and seizures associated with post-anoxic insult and are also frequently used in the treatment of febrile, acute repetitive and alcohol withdrawal seizures. Clinical advantages of these drugs include rapid onset of action, high efficacy rates and minimal toxicity. Benzodiazepines are used in a variety of clinical situations because they have a broad spectrum of clinical activity and can be administered via several routes. Potential shortcomings of BZDs include tolerance, withdrawal symptoms, adverse events, such as cognitive impairment and sedation, and drug interactions. Benzodiazepines differ in their pharmacologic effects and pharmacokinetic profiles, which dictate how the drugs are used. Among the approximately 35 BZDs available, a select few are used for the management of seizures and epilepsy: clobazam, clonazepam, clorazepate, diazepam, lorazepam and midazolam. Among these BZDs, clorazepate has a unique profile that includes a long half-life of its active metabolite and slow onset of tolerance. Additionally, the pharmacokinetic characteristics of clorazepate (particularly the sustained-release formulation) could theoretically help minimize adverse events. However, larger, controlled studies of clorazepate are needed to further examine its role in the treatment of patients with epilepsy.

Impact of CYP2C19 polymorphisms on the efficacy of clobazam therapy

Background: Clobazam-induced adverse reactions have been reported in cases with CYP2C19 defective allele(s). However, the relevance of the CYP2C19 genotypes to clobazam therapy remains to be clarified. Methods: The association between CYP2C19 genotypes and the antiepileptic and adverse effects of clobazam was retrospectively investigated in 110 Japanese subjects, in relation to clobazam and N-desmethylclobazam (N-clobazam) concentrations. Results: There were 41 (37.3%) homozygous extensive metabolizers (EMs), 44 (40.0%) heterozygous EMs, and 25 (22.7%) poor metabolizers (PMs). The response rate was significantly greater in PMs and heterozygous EMs than homozygous EMs with a gene–dose effect (65.2, 47.6 and 33.3%, respectively), and the adjusted odds ratio (95% CI) of PM versus homozygous EMs was 9.88 (2.47–39.56; p = 0.001). However, the genotypes did not affect the development of tolerance or adverse reactions, although the incidence of some adverse symptoms was insignificantly higher in PMs. The N-clobazam concentration (µg/ml) increased with the number of CYP2C19-defective alleles (0.92 ± 0.61, 2.14 ± 1.69 and 7.70 ± 6.04, respectively; p < 0.001), while the clobazam concentration was 1.5-fold greater in those with at least one variant. Conclusion: CYP2C19 genotype had an impact on the efficacy of clobazam, thus indicating that N-clobazam plays an important role in long-term clobazam therapy.

Clobazam monotherapy in drug naïve adult patients with epilepsy

PURPOSE

Evaluation of the efficacy and side effects profile of Clobazam in a 24-week open-labelled trial involving 26 cases of drug naïve adult patients with epilepsy.

METHODS

The study was an open labelled unicentre trial in which only drug naïve cases with epilepsy were included. A total of 26 cases were recruited. One case was dropped because he did not complete the desired follow up. Seizure type and frequency were recorded and follow up was done at 4, 8, 12, 18 and 24 weeks after initiation of therapy. The change in seizure severity, the dose of Clobazam required and development of side effects were recorded.

RESULTS

The seizure types included GTCS (n=16), complex partial seizures (n=4), focal motor seizures with secondary generalisation (n=3) and juvenile myoclonic epilepsy (n=2). Out of 25 patients, 16 (64%) became seizure free, while five (20%) had >50% reduction in their seizure frequency. Thus, these 21 patients (84%) were considered to be well controlled. The commonest side effect seen was sedation, which was noted in 4 of the 25 patients (16%). However, in none of these four patients sedation was significant enough to warrant stoppage of therapy. Weight gain, gait ataxia, loss of short-term memory and breakthrough seizures were noted in one patient each.

CONCLUSIONS

The efficacy of Clobazam coupled with the lack of significant side effects noted in our study makes it merit consideration as monotherapy in adult patients with epilepsy.

Pharmacokinetics and pharmacodynamics of midazolam administered as a concentrated intranasal spray. A study in healthy volunteers

AIMS

To investigate the pharmacokinetic and pharmacodynamic profile of midazolam administered as a concentrated intranasal spray, compared with intravenous midazolam, in healthy adult subjects.

METHODS

Subjects were administered single doses of 5 mg midazolam intranasally and intravenously in a cross-over design with washout period of 1 week. The total plasma concentrations of midazolam and the metabolite 1-hydroxymidazolam after both intranasal and intravenous administration were described with a single pharmacokinetic model. beta-band EEG activity was recorded and related to midazolam plasma concentrations using an exponential pharmacokinetic/pharmacodynamic model.

RESULTS

Administration of the intranasal spray led to some degree of temporary irritation in all six subjects, who nevertheless found intranasal administration acceptable and not painful. The mean (+/-s.d.) peak plasma concentration of midazolam of 71 (+/-25 ng ml-1) was reached after 14 (+/-5 min). Mean bioavailability following intranasal administration was 0.83+/-0.19. After intravenous and intranasal administration, the pharmacokinetic estimates of midazolam were: mean volume of distribution at steady state 1.11+/-0.25 l kg-1, mean systemic clearance 16.1+/-4.1 ml min-1 kg-1 and harmonic mean initial and terminal half lives 8.4+/-2.4 and 79+/-30 min, respectively. Formation of the 1-hydroxymetabolite after intranasal administration did not exceed that after intravenous administration.

CONCLUSIONS

In this study in healthy volunteers a concentrated midazolam nasal spray was easily administered and well tolerated. No serious complications of the mode of administration or the drug itself were reported. Rapid uptake and high bioavailability were demonstrated. The potential of midazolam given via a nasal spray in the acute treatment of status epilepticus and other seizure disruptions should be evaluated.

Treatment of status epilepticus

The approach to treatment of status epilepticus has changed because of the demonstration of decreased mortality with rapid intervention, completion of a randomized, double-blind VA Cooperative study comparing first-line agents, and further understanding of the pathophysiologic changes discovered in experimental animal studies. This article reviews the treatments of generalized convulsive status epilepticus in the prehospital, emergency department, and intensive care unit settings.