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A major problem in the treatment of clinical epilepsy with benzodiazepines is the development of tolerance. This is most marked with the 1,5-benzodiazepine, clobazam, but is also noted with the 1,4-benzodiazepine, clonazepam. This study examined the effects of chronic treatment with clobazam, clonazepam and the non-benzodiazepine sodium valproate on the amygdaloid kindled rat with a view to developing an animal model of tolerance. Twice daily intraperitoneal injections of vehicle (1 mL/kg), clonazepam (0.3 mg/kg), clobazam (4.0-8.0 mg/kg) or sodium valproate (200 mg/kg) were given to fully kindled rats for 12 days, in the case of clonazepam and valproate, and for 16 days for clobazam. All rats were stimulated 30-60 minutes (depending on the drug) after the morning dose. The amygdala after-discharge duration (recorded on the EEG) and the seizure stage were determined. While all three drugs initially blocked the kindled seizure, tolerance developed to clonazepam and clobazam but not to valproate. Statistical analysis of the results showed a significant linear trend in the development of tolerance to clonazepam after day 5, but tolerance to clobazam appeared in a more abrupt manner after day 2. The clobazam group were then given a further 2 days of treatment with clonazepam (0.3-0.6 mg/kg) and this blocked the kindled seizures. The amygdaloid kindled rat is a suitable model for studying tolerance to the anticonvulsant effects of benzodiazepines. Further experiments are currently in progress to examine the effectiveness of change-over therapy between clobazam and clonazepam as a means of overcoming tolerance.

Sodium valproate and clonazepam were given in combination to 17 refractory epileptic patients and their progress was reviewed clinically and by EEG's. Even though plasma concentrations of sodium valproate and conventional anticonvulsants were monitored and adjusted according to individual requirements, combination therapy consisting of valproate and clonazepam was ineffective in controlling seizures in the majority of patients. A further 40 patients receiving clonazepam were reviewed in relation to adverse reactions. 22 patients in this group suffered from undesirable effects attributable to clonazepam. These effects were managed by cessation of the drug or a reduction in the dose. The commonest side effects were drowsiness, loss of concentration, irritability and aggression.

Repeated clinical and biochemical evaluations of liver function were performed on 60 patients taking sodium valproate. No clinical evidence of liver disease was found. Biochemical abnormalities were frequently found, but they were far more common in patients treated with multiple anticonvulsants than in patients on valproate alone. A control group of patients taking phenytoin or carbamazepine monotherapy also had a high incidence of biochemical abnormalities. A group of patients started on valproate therapy 6 years previously was followed up. No evidence of liver disease was found in this group. It was concluded that biochemical abnormalities of liver function in patients receiving valproate are not progressive, and in many cases relate to the intake of other drugs. The finding of abnormal liver function tests is not necessarily an indication for ceasing valproate.

Individual dose-plasma level relationships were studied in 14 chronically treated epileptics, 10 of whom were concomitantly receiving other anticonvulsants besides valproate. Linear regression analysis showed each individual relationship to be linear with correlation co-efficients ranging from 0.9137 to 0.9997. A considerable inter-individual variation was found to exist in the slopes of the regression lines (range: 0.86 to 5.72). This may be the consequence of differences in absorption characteristics and metabolic handling of the drug. The results indicate that a proportional rise in plasma sodium valproate levels can be expected following dosage increments in an individual patient. Hourly plasma sodium valproate measurements for 6 hours between 2 successive doses, in the same group of patients, showed that the mean percentage change in post-dose peak plasma levels was 44.5%, and range from 20.7 to 153.5%. Plasma levels returned to values close to pre-dose starting levels 6 hours after the administration of a dose. The large degree of inter-dose fluctuation between doses indicates that it is preferable to use pre-dose plasma sodium valproate levels to guide the clinical management of epileptic patients.

A benzodiazepine drug, clobazam, was evaluated in 14 refractory epileptic patients, nine of whom received the drug double-blind. Ten patients have been given clobazam long enough to assess results. Four showed marked benefit, four failed to respond and two showed a transient benefit which was maintained by dose changes of both clobazam and clonazepam. Side effects were minimal; doses ranged from 15 to 60 mg per day. Clobazam may have place in the treatment of the Lennox Gastaut syndrome and other types of refractory seizures.

The recent discovery that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes a syndrome of Parkinsonism in man and monkey has stimulated the search for a small animal model of Parkinsonism. In this study, MPTP was administered to a series of small animals and observations made on clinical and neurochemical changes. The clinical effects of MPTP in rabbits, guinea pigs, and rats were short lived, and no chronic Parkinsonian syndrome developed. The C57 black mouse, however, although also not showing clinical changes, proved to be an ideal neurochemical model in which to study the effects of MPTP since striatal dopamine levels were reliably reduced to 13% of control values after 4 intraperitoneal injections of 30 mg/kg MPTP. Pathological study of the striatum and substantia nigra in the mouse model failed to show any alteration in neuronal morphology or numbers. Although the effect of MPTP on striatal dopamine lasted for up to 2 weeks after the last MPTP injection, the possibility exists that no neurotoxic effects occur and the observed dopamine depletion is pharmacological only.

The broad results of the treatment of patients with idiopathic Parkinson's disease who have received levodopa or its variants are reported. 50 patients, 24 males and 26 females, with a mean age of 66.5 years were treated with levodopa, in daily doses ranging from 0.25g to 6.0g or 'Sinemet' in daily doses of 300mg to 750mg. Periods of treatment ranged from 4 months to 8 years, with a mean of 4.02 years. The relationships of patients' age, onset of Parkinsonian symptoms and interval between initial treatment with levodopa and the current clinical state were studied. Patients were classified according to their clnical response into 3 categories: satisfactory response, progressive deterioration or intolerance of levodopa. The proportion of patients in each category was 66%, 22% and 12% respectively. The clinical results of treatment correlated with those of Webster Disability Testing Scale. Analysis showed that the majority of patients tolerated levodopa and showed an initially satisfactory response. Patients who responded well were considerably younger than those who failed to respond. Patients receiving the drug for a shorter period (less than 3 years) showed a better response. After 3 years' treatment, the response declined. Patients who had had Parkinson's disease for more than 4 years appeared to do less well than those with recently diagnosed disease, but many patients responded well even when treatment was initiated 10 years after the onset of symptoms. Patients discontinued levodopa treatment because of psychoses, nausea, dyskinesia or exacerbation of urinary incontinence. The commonest side effects were nausea (34%), postural hypotension (22%), psychoses (10%) and 'on-off' phenomena in 12% of patients.

The value of continuous ambulatory EEG monitoring in the management of patients with seizures was assessed. Eighty-seven patients were studied over a two-year period, and 198 recordings were made. In six patients data from the monitor record changed management significantly by suggesting a diagnosis other than that made clinically and by routine EEG. In a further 33 patients data strongly supporting the clinical diagnoses were obtained. In 47 patients no positive diagnostic data were obtained, and in one patient the data could not be reconciled with the clinical picture. The ambulatory EEG was particularly useful for detecting nocturnal fits, such as tonic seizures, and for differentiating genuine seizures from pseudoseizures. Limitations of the instrument include the presence of only four channels and some distortion and degradation of the EEG signal. In spite of these problems, the instrument was found to be a valuable aid in the evaluation of patients with seizures.