Clonazepam in the treatment of epilepsy

Neuropsychological deficits in childhood epilepsy syndromes

Seizure disorders are relatively common in childhood, and the International League Against Epilepsy (ILAE) provides a hierarchical classification system to define seizure types. At the final level of classification, specific epilepsy syndromes are defined that represent a complex of signs and symptoms unique to an epilepsy condition. The present review discusses the issues related to several of these epilepsy syndromes in childhood, including those classified as generalized idiopathic epilepsies (e.g., childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy), focal epilepsies (benign rolandic epilepsy, occipital epilepsy, temporal lobe epilepsy, frontal lobe epilepsy) and the "epileptic encephalopathies," including Dravet's Syndrome, West Syndrome, Lennox-Gastaut Syndrome, Myoclonic Astatic Epilepsy, and Landau-Kleffner Syndrome. For each syndrome, the epidemiology, clinical manifestations, treatments, and neuropsychological findings are discussed.

Neuropsychological deficits in childhood epilepsy syndromes

Seizure disorders are relatively common in childhood, and the International League Against Epilepsy (ILAE) provides a hierarchical classification system to define seizure types. At the final level of classification, specific epilepsy syndromes are defined that represent a complex of signs and symptoms unique to an epilepsy condition. The present review discusses the issues related to several of these epilepsy syndromes in childhood, including those classified as generalized idiopathic epilepsies (e.g., childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy), focal epilepsies (benign rolandic epilepsy, occipital epilepsy, temporal lobe epilepsy, frontal lobe epilepsy) and the "epileptic encephalopathies," including Dravet's Syndrome, West Syndrome, Lennox-Gastaut Syndrome, Myoclonic Astatic Epilepsy, and Landau-Kleffner Syndrome. For each syndrome, the epidemiology, clinical manifestations, treatments, and neuropsychological findings are discussed.

Efficacy and safety of clonazepam in refractory neurally mediated syncope

Neurally mediated syncope is a complex syndrome that is often difficult to manage using currently available treatment strategies. The efficacy and safety of clonazepam was evaluated in 35 patients with refractory neurally mediated syncope. All patients had syncope (n = 33) or disabling presyncope (n = 2) and a positive head-up tilt table test (HUTT) despite treatment with one or more of the following therapies: beta-blocker, high-salt diet, fludrocortisone, elastic compression stockings, and disopyramide. Clonazepam was initiated at 0.5 mg/day and titrated in 0.25-0.5 mg/day increments for symptom control. Early (first 8 weeks) symptomatic response was achieved in 31 of 35 (89%) patients. Early HUTT reverted to negative in 29 of 35 (83%) patients. Two patients discontinued clonazepam during early follow-up due to side effects. Thirty-three patients received long-term clonazepam therapy. Twenty-five patients had late HUTT with 21 remaining negative. Of the eight patients who did not have late HUTT, one patient discontinued clonazepam prior to HUTT due to side effects. Seven patients refused late HUTT. All seven patients achieved symptomatic control on clonazepam with two requiring dose titration. Of the 21 patients with a negative late HUTT, 18 achieved symptomatic control with two of these patients requiring dose titration. Two patients who had only partial symptom control despite dose titration achieved total symptomatic control with the addition of disopyramide and beta-blockers. Two patients with a negative late HUTT discontinued clonazepam due to side effects. One patient had been symptomatically controlled while the other had recurrent symptoms with dose limiting side effects occurring after clonazepam dose titration. In the 4 patients with a positive late HUTT, 2 patients were symptomatically controlled, 1 patients required combination therapy with a beta-blocker to achieve symptomatic control, and 1 patient discontinued therapy due to side effects. Overall, 29 of 35 (83%) patients continue to receive clonazepam with symptom control. Based on intention-to-treat HUTT results, 21 of 35 (60%) patients were responders. Four patients required clonazepam dose titration and three required combination therapy with clonazepam plus disopyramide and/or a beta-blocker to achieve control. Clonazepam was discontinued in 6 patients, 5 for side effects and 1 following a transient ischemic attack. Clonazepam appears to be an effective therapeutic alternative in patients with refractory neurally mediated syncope. Based on our preliminary findings, a placebo controlled evaluation of clonazepam in neurally mediated syncope is warranted.

Seizures with clonazepam: discontinuation and suggestions for safe discontinuation rates in children

Clinical characteristics of clonazepam (CZP) discontinuation seizures were clarified from 17 patients who developed seizure exacerbation after rapid discontinuation, including abrupt discontinuation, reduction, or replacement with nitrazepam (NZP). Safe discontinuation rates of CZP were estimated by comparing these patients with 23 patients without CZP discontinuation seizures. The seizures consisted of status epilepticus or frequent attacks of generalized tonic-clonic seizures (GTC) or non-GTC, and the first attack of GTC. Incidence did not differ significantly between CZP-effective cases and CZP-ineffective cases at discontinuation. The reasons for abrupt discontinuation included adverse effects, insufficient efficacy, difficulty in taking CZP owing to pneumonia, or carelessness of the doctors or the families. Seizure exacerbation occurred 1-6 days after CZP discontinuation. Most of the problems improved with readministration of the original or smaller dosages of CZP or of NZP in an amount threefold or more greater than the original CZP dose. Safe discontinuation rates were estimated to be < or = 0.04 mg/kg for abrupt discontinuation, < or = 0.04 mg/kg/week for reduction, and replacement with NZP of 2.5 or more times the original amount of CZP. These safe discontinuation rates were prospectively confirmed by 84 cases of CZP discontinuation in 54 other patients, and no seizure exacerbation occurred with these discontinuation rates.

Discontinuation of clonazepam after long-term treatment

Frequent unwanted side effects and development of tolerance are the main disadvantages of clonazepam (CZP) in long-term treatment of epileptic patients. A review of the literature shows that CZP tolerance more often appears in severe forms of childhood epilepsy (West and Lennox-Gastaut syndromes) than in other epileptic syndromes. We prospectively studied the consequences of CZP discontinuation in 40 consecutive children with difficult-to-treat epilepsies and multiple-drug therapy. The CZP was reduced stepwise in a variable daily reduction rate (0.003-0.16 mg/kg), while serum levels of the comedication were kept unchanged. In only three children (7.5%), CZP was believed to have had some antiepileptic effect; in 30 (75%) it had been ineffective, whereas in six (15%), a decrease in seizure frequency after CZP discontinuation even suggested a negative therapeutic effect. Discontinuation symptoms, mostly in the form of a transitory exacerbation of seizure frequency, occurred in 19 children (47.5%). These children had a significantly higher CZP dose and longer duration of treatment than did children without discontinuation symptoms, but there was no difference between the two groups related to the rate of CZP discontinuance.

Adverse behavioral response to clonazepam as a function of Verbal IQ-Performance IQ discrepancy

Eight of 38 consecutive patients who received clonazepam had significant behavioral side effects. In these 8 patients, the mean absolute IQ discordance between Verbal IQ (VIQ) and Performance IQ (PIQ) was 17.5 points. Thirty of 38 patients had no adverse behavioral side effects while receiving clonazepam. In these 30 patients, the mean absolute VIQ-PIQ discrepancy was 6.5 points. Full neuropsychological testing had been performed on all patients. The only test variable showing a statistically significant difference was the absolute discrepancy between VIQ and PIQ (P less than 0.0001).

Treatment of the nonconvulsive epilepsies

Eliminating seizures should be the first goal of therapy for nonconvulsive epilepsies, but preventing seizures, i.e., guarding against head injuries and immunizing against agents that attack the nervous system, is the second goal. An accurate diagnosis of seizure type helps ensure that the appropriate medication for that particular form of epilepsy will be prescribed. Drug decisions should also be based on the risk: benefit ratio to the individual patient, and drug interactions should be considered when more than one drug is required. Frequent monitoring of drug serum levels is necessary in the case of multiple drug therapy or until seizures are controlled. Ethosuximide is considered the drug of choice in absence seizures, but valproic acid is equally effective. Although effective in controlling absence seizures, clonazepam is not favored in this indication because of a high incidence of side effects and the development of tolerance. Atonic seizures are generally refractory to treatment, but valproate, clonazepam, and occasionally carbamazepine represent the drugs of choice in management. Phenytoin continues to be a very popular drug for most types of seizures, but carbamazepine, used adjunctively until recently, is effective as monotherapy for the control of partial seizures, particularly those of the complex partial variety.

Pharmacokinetics and side-effects of clonazepam and its 7-amino-metabolite in man

Clonazepam (CNP) and its principal metabolite in plasma, 7-amino-CNP (ACNP), have been investigated in a prospective study of 27 newly diagnosed epileptics and correlated with specified side-effects. At a daily dose of 6 mg, the average plasma levels of both substances were about 50ng/ml, and individual values ranged from 30 to about 80 ng/ml. There was a linear correlation between changes in dose and the resulting plasma levels, which indicates first order elimination kinetics. Side-effects were frequent, but neither their severity nor their occurrence could be related to plasma levels or to the rate of increase in plasma concentration of the drug. Three out of five patients who developed serious dysphoria had significantly high CNP levels. The concentration of ACNP was considerably increased in four patients who subsequently suffered from withdrawal symptoms. Drug interaction with diphenylhydantoin, i.e. decreased CNP level, was observed in all five patients who received both compounds. In general it is not yet possible to define an upper limit for the plasma levels of CNP and ACNP at which toxicity occurs. In patients treated with conventional doses of CNP, measurement of plasma concentration is not required, except in special circumstances, because of the lack of correlation between plasma level and side-effects.