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At least 19 recordsLinked to original sources
PubMed1979

[Direct determination of clonazepam (Rivotril) and 7-amino clonazepam in plasma by gas-chromatography (author's transl)].

A method is developed for direct gas-chromatographic determination of clonazepam (Rivotril) and its main metabolite, 7-amino clonazepam, in plasma, using desmethylflunitrazepam as internal standard. Following selective extraction, the benzodiazepines are analyzed by gas-chromatography, with a glass column filled with 3% OV17 on Gas Chrom Q and 63Ni electron capture detector. The procedure, which requires neither hydrolysis nor derivatisation, has a good selectivity. The sensitivity is 5 ng/ml of plasma for a valid quantitative determination. We have to improve this limit for fine pharmacokinetic studies, but the method is already available for therapeutic and pharmacovigilance controls. It is also suitable for diagnostic of eventual overdosing or poisoning, based on plasma or urine analysis.

Benzodiazepinones↗
PubMed1976

[Central effects of clonazepam].

The effects of oral administration of clonazepam, a new benzodiazepine derivative (F. Hoffmann-La Roche), on the central nervous system were compared with those of diazepam and several anticonvulsants in mice and rats. 1) Clonazepam exhibited a moderate inhibitory effect on the locomotor activity observed with open-field situation in mice and no effect in rats, while it inhibited markedly the rearing behavior in both animals, the duration of action being approximately six hours. 2) Clonazepam potentiated the methamphetamine-induced hyper-locomotor activity in mice whereas trimethadione had no effect. 3) Clonazepam inhibited with a moderate potency the conditioned avoidance response and response to a fixed-ratio (FR 20) schedule of food reinforcement in rats, the potency being a little weaker than that of diazepam. 4) The muscle relaxant effect of clonazepam determined by the traction test was slightly more potent as compared with that of diazepam. Thiopental hypnosis was markedly potentiated after clonazepam. 5) The clonic (CL), tonic-flexor (TF) and extensor convulsions (TE) induced by pentetrazol were strongly inhibited after clonazepam in mice, anticonvulsant potency against CL and TE of clonazepam being approximately 23 and 21 times stronger than that of diazepam, 3333 and 3846 times that of trimethadione, and over 3047 and 178 times that of phenytoin, respectively. Clonazepam reduced markedly CL and TE elicited by bemegride with about 12 to 14 times stronger potency than diazepam. On the contrary, the anticonvulsant effect of clonazepam against TE of maximal electroshock seizure evoked by supramaximal current was weak, the potency being 0.71 times weaker than that of phenacemide, 0.14 times than phenytoin and 0.24 times than phenobarbital. By the combined administration of clonazepam with other anticonvulsants such as trimethadione and phenytoin against pentetrazol convulsion, and phenacemide, phenytoin and phenobarbital against maximal electroshock seizure, the antagonistic effect of these anticonvulsants was potentiated by 4 to 5 times. 6) The acute toxicity (LD50) of clonazepam was weak but that of phenacemide or phenytoin was potentiated to a certain degree by combined administration with clonazepam. The results suggest that clonazepam has a psychopharmacological profile similar to that of benzodiazepines with a particularly potent anticonvulsant effect on pentetrazol and bemegride convulsions, and the anticonvulsant effect is synergic with that of other anticonvulsants.

Animals↗
PubMed1977

Radioimmunoassay of the anticonvulsant agent clonazepam.

A simple and specific radioimmunoassay was developed for the determination of the anticonvulsant agent clonazepam directly in plasma without extraction. Antibodies to clonazepam were produced in rabbits after immunization with an immunogen prepared by covalently linking the 3-hemisuccinyloxy derivative of clonazepam to bovine serum albumin. When employing 3H-clonazepam as the tracer, the radioimmunoassay has a limit of sensitivity of 5 ng/ml using a 0.1-ml sample of plasma. The antibodies exhibited a high degree of specificity for clonazepam; no cross-reactivity was observed with its 7-amino and 7-acetylamino metabolites nor with a number of other widely prescribed anticonvulsant agents that might be administered in conjuction with clonazepam. Satisfactory agreement was obtained for the plasma levels of clonazepam in humans when samples were assayed by the radioimmunoassay and an established electron-capture GC technique. By virtue ot its simplicity, the radioimmunoassay offers a distinct advantage to the clinician for monitoring plasma clonazepam levels and the compliance of patients undergoing anticonvulsant therapy with the drug.

Animals↗
PubMed1976

[Antiepileptic activity of clonazepam--an antiepileptic benzodiazepine derivative].

Clonazepam, an antiepileptic benzodiazepine derivative was administered into 30 patients mainly with incurable type epilepsy. Results were as summarized below: (1) Clonazepam was effective in 44.4% of 36 cases of seizures. The initial effect was noticed in 55.6%. (2) Clonazepam was proved to have a broad spectrum in its efficacy. It showed the highest rate of effectiveness, 71.4%, on psychomotor seizures. (3) Clonazepam was effective in all 4 cases of the photogenic epilepsy which shows the photosensitivity in the EEG. With the exception of 1 case, the sensitivity in the EEG also disappeared responding to clonazepam. (4) The Jacksonian type of the partial motor seizure disappeared in 2 cases after the administration with clonazepam. (5) The effects of clonazepam of EEG were examined in 24 patients. The abnormality of the basic activity, the diffuse epileptic discharge and the focal epileptic discharge were improved in 29.2%, 61.5% and 66.7%, respectively. In addition, the rate of the clinical effectiveness was high in the cases with the centrencephalic discharge. (6) Side effects were observed to have appeared in 38.9% of the patients. They were mostly drowsiness and ataxia. (7) Based on the above-mentioned results, it can be claimed that clonazepam is effective on psychomotor seizures, photogenic epilepsy and the secondary type of generalized convulsion (Jacksonian).

Adolescent↗
PubMed1978

Time-course of interaction between carbamazepine and clonazepam in normal man.

The applicability of a pharmacokinetic model for drug interactions by enzyme induction was tested by chronic dosing situation using carbamazepine (Tegretol) as the inducer and clonazepam (Clonopin) as the drug affected. Seven healthy subjects received one 1.0 mg clonazepam tablet once a day for 29 days and one 200 mg carbamazepine tablet once a day from days 8 to 29. Plasma levels of clonazepam were measured by electron-capture gas-liquid chromatography and those of carbamazepine and its epoxide metabolite by gas chromatographic-chemical ionization-mass spectrometry. Clonazepam plasma levels reached an initial steady-state by day 7 and declined to a lower steady-state over 5 to 15 days after additions of carbamazepine. The decrease in clonazepam levels ranged between 19% and 37%. Autoinduction of carbamazepine metabolism was also evident. Urinary excretion of D-glucaric acid increased 2- to 4-fold following carbamazepine administration (p less than 0.005). This increase provided additional evidence that the present interaction was due to enzyme induction. Experimental clonazepam levels were fitted to an induction pharmacokinetic model for multiple dosing with an exponentially increasing clearance. Induced half-lives of clonazepam (mean = 22.5 +/- 11.5 hr) were shorter (p less than 0.005) than control values (32.1 +/- 16.6 hr). Apparent enzyme(s) turnover half-lives ranged between 1 and 6 days.

Adult↗
PubMed1979

Antimyoclonic action of clonazepam: the role of serotonin.

Clonazepam (5-(2-chlorophenyl)-1,3-dihydro-7-nitro 2H-1,4 benzodiazepin-2-one) (2 mg/kg) reduced a p,p'-DDT-induced myoclonus in mice by 50%. This antimyoclonic action of clonazepam was counteracted by the serotonin (5-HT) receptor blockers methysergide, metergoline and cinnanserin and potentiated by the 5-HT uptake inhibitors fluoxetine and chlorimipramine. Clonazepam (4 mg/kg) reduced plasma tryptophan by 27%, but had no effect on brain tryptopham, 5-HT, 5-hydroxyindoleacetic acid, 5-HT synthesis and 3H-5-HT receptor binding. Clonazepam (10(-5) M) inhibited brain synaptosomal 3H-5-HT uptake by 23% and increased 3H-5-HT release by 24%. However, 2-8 mg/kg of clonazepam administered intraperitoneally had no effect on 5-HT uptake or release. gamma-Aminobutyric acid (GABA) agonists (muscimol, acetylenic GABA, amino-oxyacetic acid) and the GABA antagonists bicuculline and isoniazid had no effect on p,p'-DDT-induced myoclonus. Furthermore, bicuculline did not counteract the antimyoclonic effect of clonazepam. We suggest that the antimyoclonic action of clonazepam is mediated by enhancement of serotonergic rather than GABAergic neurotransmission.

Animals↗
PubMed1978

[Influence of clonazepam, an anticonvulsant benzodiazepine drug, on the rat brain monoamine containing neurons especially on dopaminergic neurons (author's transl)].

Clonazepam at two doses of 1 mg/kg i.p. significantly decreased 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) contents in the rat caudatus and cortex but not so in the olfactory tubercle, septum and hypothalamus. The drug decreased dopamine (DA) turnover rate in the caudatus, but did not inhibit tyrosine hydroxylase activity. The drug significantly enhanced stereotyped behavior induced by apomorphine and d-methamphetamine. Clonazepam enhanced apomorphine-induced decrease in striatal HVA, and cortical DOPAC and HVA contents, and d-methamphetamine-induced decrease in cortical DOPAC content. Reserpine pretreatment did not affect apomorphine-induced stereotypy and its enhancement with clonazepam. The drug did not activate adenylate cyclase nor DA-sensitive adenylate cyclase in the striatal homogenates and did not change cyclic AMP content in the caudatus. The drug inhibited phosphodiesterase activity in caudate and cortical homogenates but not in vivo. Clonazepam did not alter ChAc and AChE activities in the caudatus, 6 other cerebral regions and the spinal area. Clonazepam also decreased NE turnover in the caudatus and 5-HIAA contents in the brainstem area. These neurochemical and behavioral effects of clonazepam indicate probable postjunctional DA stimulation in the striatum and cortex of the type not linked with adenylate cyclase and phosphodiesterase but probably due to activation of inhibitory gamma-amino butyric acid (GABA) neurons on the strio-nigral pathway.

Acetylcholinesterase↗
PubMed1976

Clonazepam in the treatment of epilepsy. A clinical long-term follow-up study.

Sixty-eight patients with various types of epileptic seizures have been treated with clonazepam (Rivotril). Fifty-four patients could be evaluated. In 44 patients, clonazepam was used as a supplement to insufficient previous medication. Ten patients received clonazepam alone. The mean duration of treatment was 2 years and 7 months. Thirty-three patients are still on clonazepam, with a mean duration of treatment of 3 years and 4 months. In 34 patients (63%) a reduction of more than 50% was seen in the seizure frequency of the only type suffered by a patient, or of one of several types. No significant decrease in antiepileptic potency with time was observed. Medication was withdrawn in a total of 21 of the 54 patients because of freedom from seizures (2 patients), lack of effect (7 patients), increased frequency of seizures (3 patients), or lack of cooperation and/or side-effects (3 patients). In 5 patients, the drug may have provoked new types of epileptic seizure. This long-term follow-up study seems to substantiate the favorable antiepileptic properties of clonazepam.

Adolescent↗
PubMed1977

Clonazepam, baclofen and placebo in the treatment of spasticity.

25 patients with multiple sclerosis (MS) and other spastic disorders, 33 MS patients and 10 control patients with MS were given clonazepam, baclofen or placebo over a period of 5 days to 20 weeks. Both clonazepam and baclofen were significantly more effective than placebo in the treatment of spasticity (p less than 0.005 or p less than 0.01). A clinical trial of clonazepam versus baclofen was carried out and this showed no significant difference between the two drugs. However, there was indication that clonazepam influenced with better improvement in patients with slight muscle hypertonia mainly of cerebral origin. Patients with more severe forms, mainly of spinal spasticity, benefited rather from baclofen treatment (Fisher's test, p = 0.003). There was suggestion that combination of the two drugs may be more effective in some patients than than clonazepam or baclofen alone.

Adolescent↗
PubMed1976

Clonazepam: a review of its pharmacological properties and therapeutic efficacy in epilepsy.

Clonazepam or 5-(2-chlorphenyl)-1, 3-dihydro-7-nitro-2H-1,4benzodiazepin-2-one, is a close structural and pharmacological relative of nitrazepam. It has a broad spectrum of activity against the various types of epilepsy, and is effective in many patients whose condition has proved resistant to other antiepileptic drugs. Its chief uses are in status epilepticus, in which intravenous clonazepam may replace diazepam as the drug of first choice, and in the minor motor seizures of childhood, particularly petit mal absences, the Lennox-Gastaut syndrome and infantile spasms. Clonazepam is also at least as effective as current treatment in psychomotor and myoclonic epilepsies, but seems unlikely to replace phenytoin and the barbiturates in the treatment of grand mal or focal motor seizures except in patients resistant to standard therapy. Initial success with clonazepam can be followed by loss of effect, but benefit can often be restored, at least initially, by temporary interruption and re-institution of treatment. Side-effects are common with clonazepam. Most patients experience drowsiness and fatigue, which are frequent causes of withdrawal, together with lesser incidences of ataxia, dystonia, hypotonia, and hyperactivity. These effects usually disappear with continued therapy, and are minimised by gradual introduction of the drug over 2-4 weeks. Hypersalivation and excessive bronchial secretion may be a problem in children and infants.

Absorption↗
PubMed1978

Improved micromethod for determination of underivatized clonazepam in serum by gas chromatography.

We describe a gas-chromatographic micromethod, with use of a solid injection system and an electron capture detector, for determination of underivatized clonazepam in serum. Vigorous mixing of 100 microliter of serum with 20 microliter of borate buffer (pH 9.0) and 100 microliter of a cyclohexane/dichloromethane mixture (4/6 by vol) containing methyl nitrazepam as internal standard suffices to extract 86% of the clonazepam into the organic layer. We obtained a linear response curve for clonazepam in serum in the concentration range 5 to 150 microgram/liter. The lowest detectable concentration by our method is about 1 microgram/liter of serum. Interference by several anticonvulsant drugs, metabolites, and related compounds was investigated. The assay is simple, rapid, and suitable for clinical routine determination of clonazepam in serum in therapeutic concentrations. We illustrate the steady-state concentration of clonazepam in serum during chronic oral administration to 28 patients.

Benzodiazepinones↗
PubMed1977

An 125I-radioimmunoassay for the determination of the anticonvulsant agent clonazepam directly in plasma.

A simple and specific 125I-radioimmunoassay (RIA) for the determination of the anticonvulsant agent clonazepam directly in plasma has been developed using a previously reported antiserum to the drug. The 125I-radioligand was prepared by reaction of 3-aminoclonazepam with a commercially available acylating reagent, 125I-N-succinimidyl 3(4-hydroxyphenyl) propionate, of high specific activity (approximately 1500 Ci/mM). The method has a workable range between 5 and 100 ng/ml of clonazepam using a 10 mu1 sample of plasma for analysis, which is satisfactory for routine clinical monitoring. The intra and inter-assay coefficients of variation did not exceed 3 and 9% respectively. Recovery of clonazepam was quantitative when the drug was added to a pool of plasma obtained from subjects who had received a wide variety of other anticonvulsants. Clinical plasma samples from subjects receiving clonazepam chronically were assayed for clonazepam by the new 125I-RIA and a previously reported 3H-RIA. The data was subjected to linear regression analysis which gave a slope, intercept and correlation coefficient of 1,-0.33 ng/ml and 0.994 respectively and demonstrated that the two methods are equivalent. However, the 125I-RIA is more rapid and less costly for routine monitoring than the 3H-RIA.

Benzodiazepinones↗
PubMed1976

Clonazepam in the treatment of epilepsy. A controlled clinical trial in simple absences, bilateral massive epileptic myoclonus, and atonic seizures.

In a controlled clinical investigation based on ten patients with simple absences and ten patients with myoclonic atonic seizures, all patients who had insufficient response to conventional antiepileptic treatment received clonazepam (Rivotril [Denmark]; Clonopin, comparable US product) combined with previous antiepileptic drugs. The effects of the combined use of clonazepam and the previous antiepileptid drugs were compared with the effects of placebo combined with the same drugs. The trial was single-blind crossover with sequential analysis. In a daily dose of usually 3 to 6 mg, depending on patient age, the antiepileptic effect of clonazepam was significantly superior to placebo and was estimated as remarkably good. Side-effects of somnolence, fatigue, drowsiness, and coordination disturbances occurred in most of the patients, but subsided spontaneously or could be controlled by slow increase or slight reduction of dosage. Mental sideeffects such as agitation, confusion, and aggressiveness were more troublesome and caused discontinuation of clonazepam in two patients.

Adolescent↗
PubMed1979

Kinetics of biotransformation of clonazepam to its 7-amino metabolite in the monkey.

The pharmacokinetic behavior of the 7-amino metabolite of clonazepam administered exogenously and formed endogenously from the parent drug was studied in a group of rhesus monkeys using constant rate intravenous infusions. Plasma levels of the 7-amino metabolite and/or clonazepam were determined with a GC-CI-MS method. The biological half-life of the 7-amino metabolite (2.2 +/- 1.0 hr) was shorter than that of clonazepam (4.9 +/- 0.2 hr). Total body clearance of the metabolite (0.83 +/- 0.16 liters/hr/kg) was larger than that of the parent drug (0.55 +/- 0.09 liters/hr/kg). The kinetics of in vivo biotransformation were described by a two-compartment model in which formation and disposition of the metabolite follow first-order processes. The fraction of a dose of clonazepam appearing in the systemic circulation as 7-amino metabolite was 0.70 +/- 0.30. This value may underestimate the actual fraction formed, if the metabolite is susceptible to first-pass metabolism following in situ formation.

Amines↗
PubMed1977

Lack of effect of clonazepam on serum levels of diphenylhydantoin, phenobarbital and carbamazepine.

The influence of clonazepam on steady-state serum levels of diphenylhydantoin, phenobarbital and carbamazepine was studied in 22 patients with epilepsy receiving one or two of these drugs. Clonazepam was given in slowly increasing doses for 2 weeks until a maximum dose of 4-6 mg per day was reached; thereafter the dose was kept constant. The serum levels of diphenylhydantoin, phenobarbital and carbamazepine were determined once a week for at least 6 weeks. During clonazepam medication in ordinary doses the serum levels of the drugs in question were unaltered. Thus, it is unlikely that the antiepileptic effect of clonazepam in these patients even partly may be due to increased serum levels of these other drugs mentioned.

Adolescent↗
PubMed1977

Treatment of epilepsy with clonazepam and its effect on other anticonvulsants.

Clonazepam was added to the treatment of patients with poorly controlled epilepsy in a double-blind trial and an open trial. Considerable improvement occurred with patients with myoclonic jerks and tonic-clonic convulsions, and with photosensitive epilepsy. Patients with atypical petit mal and focal epilepsies also improved. Drowsiness was initially common but lasted only a short time. No evidence was found for an action of clonazepam on the metabolism of other drugs, but treatment with phenobarbitone lowered serum concentrations of clonazepam. We conclude that clonazepam is particularly valuable in epilepsy with associated myoclonsu and in photosensitive epilepsy.

Adolescent↗
PubMed1977

Concentration of clonazepam in serum and cerebrospinal fluid of the sheep.

Following intravenous administration of clonazepam to sheep there was rapid equilibration of cerebrospinal fluid and unbound serum concentrations of the drug. The pharmacokinetics of clonazepam in sheep describe a 2-compartment model and the large volume of distribution suggests tissue binding of clonazepam. There was wide variation in serum concentration and at least 2 mg of clonazepam was necessary to attain the recommended therapeutic concentration.

Animals↗