Single-dose pharmacokinetics of Madopar HBS in patients and effect of food and antacid on the absorption of Madopar HBS in volunteers

Pharmacokinetic studies in parkinsonian patients and healthy volunteers have shown that Madopar HBS behaves as a slow-release formulation of L-dopa and benserazide. In comparison with standard Madopar the rate of absorption is reduced, providing lower peak concentrations of L-dopa. The drug is released and absorbed over a period of 4-5 h, thus maintaining substantial plasma concentrations for 6-8 h after dosing. Although the bioavailability after oral dosing is reduced as compared with standard Madopar (60-70%), this difference seems to be due to incomplete absorption rather than altered disposition of the drug. The presence or absence of food in the stomach has no effect on the absorption of L-dopa from Madopar HBS, but administration of antacids further reduces the bioavailability (45%).

Single-dose studies of a slow-release preparation of levodopa and benserazide (Madopar HBS) in Parkinson's disease

The clinical effects and pharmacokinetic profiles of single doses of Madopar HBS were compared with those of standard Madopar in two studies in patients with Parkinson's disease and 'on-off' fluctuations. In the first study, 10 fasting patients received equivalent doses (200 mg levodopa plus 50 mg benserazide) of each preparation. The clinical response to Madopar HBS was delayed and brief; the relative bioavailability was only 50%. In the second study in 7 non-fasted patients, the effects of 3 capsules of Madopar HBS 125 were compared with those of 2 capsules of standard Madopar 125. Delay to turn on was longer with HBS, but duration of time on, and delay to turn off, were longer with this preparation. The area under the concentration-time curve for plasma levodopa was greater with HBS, and the maximum levodopa concentration was similar to, but achieved later than standard Madopar.

Open study of Madopar HBS, a new formulation of levodopa with benserazide, in 13 patients with Parkinson's disease and 'on-off' fluctuations

In a open study in 13 patients with Parkinson's disease with 'on-off' fluctuations, all (n = 3) or part (n = 10) of the usual intake of levodopa (with peripheral decarboxylase inhibitor) was replaced by Madopar HBS for 5-122 days (median 35). Time 'off' increased in 2 of the 3 monotherapy subjects. With combined therapy, time 'on' was increased in 6, unchanged in 2 and reduced in 2. However, 11 of the 13 patients complained of reduced predictability of clinical response with Madopar HBS. Only 4 of the 13 patients preferred to continue with combined standard plus HBS treatment; this continued treatment led to an increase in time 'on' in 3 and a decrease in involuntary movements in 3 patients. Two of these four patients benefited on both counts.

Anticholinergic-induced chorea in the treatment of focal dystonia

The occurrence of chorea, induced by trihexyphenidyl (benzhexol hydrochloride) during the treatment of five adult patients who had focal or segmental dystonia, is described. The dose at which chorea appeared ranged from 15 to 60 mg/day (mean 31.7 mg/day). All but one patient had developed common adverse effects of this drug (dry mouth, blurred vision, and confusion) at lower doses (mean 21.8 mg per day). There was an inverse relationship between the age of the patient and the dose of trihexyphenidyl at which chorea developed.

Olfactory threshold in Parkinson's disease

Olfactory threshold to differing concentrations of amyl acetate was determined in 78 subjects with idiopathic Parkinson's disease and 40 age-matched controls. Impaired olfactory threshold (previously reported by others) was confirmed in Parkinsonian subjects compared with controls. There was no significant correlation between olfactory threshold and age, sex, duration of disease, or current therapy with levodopa or anticholinergic drugs. In a sub-group of 14 levodopa-treated patients with severe "on-off" fluctuations, no change in olfactory threshold between the two states was demonstrable. Olfactory impairment in Parkinson's disease may involve mechanisms that are not influenced by pharmacologic manipulation of dopaminergic or cholinergic status.

Painful Parkinson's disease

A number of patients with Parkinson's disease complain of severe and distressing pain. Many of them are referred for psychiatric or other inappropriate treatment. The key diagnostic clue to the origin of the pain is that in almost all cases it fluctuates in parallel with the motor changes associated with levodopa treatment. The nature of this temporal association in the individual case, as well as aiding diagnosis, often indicates the need for appropriate modifications in antiparkinsonian therapy, which can be far more effective than conventional analgesic treatments.

Familial dystonia and visual failure with striatal CT lucencies

A unique disorder is described in seven members of two families in whom dystonia was variably associated with subacute visual loss or asymptomatic optic atrophy, and striking bilateral symmetrical lucencies on CT scan, especially involving the putamen. It is possible that this is a variant of Leigh's disease. However, there were considerable differences between these patients and those with pathologically proven Leigh's disease. This condition must be excluded in all patients thought to have idiopathic dystonia, subacute visual failure similar to Leber's optic neuropathy, or a combination of these disorders.

Repeated levodopa infusions in fluctuating Parkinson's disease: clinical and pharmacokinetic data

The short-term efficacy of continuous intravenous infusions of levodopa (with oral peripheral decarboxylase inhibitor) in abolishing or reducing "on-off" fluctuations in patients with Parkinson's disease is well established. However, there are suggestions that clinical response may be less good with longer infusions, or infusions on consecutive days. We therefore gave intravenous infusions of levodopa to three such subjects on five consecutive days (6 h on day 1, 12 h/day on days 2 to 5). One subject's symptoms were perfectly controlled, one experienced one "off" period per day, and the third developed one or two off-periods per day. Nevertheless, clinical control in all three subjects was superior with levodopa infusions to that seen on optimum oral therapy. Plasma levodopa concentrations during the infusions could be correlated with off to on, and with on to off switches. In general, subjects needed higher plasma levodopa levels to turn "on" than to keep them mobile once on, and the threshold levels below which off-periods supervened were lower still. These experiments show that repeated intravenous infusions of levodopa are very effective in some parkinsonian subjects, who may be suitable candidates for prolonged parenteral treatment with alternative, more highly soluble, dopaminergic drugs.

Menstrual-related fluctuations in Parkinson's disease

Eleven of 12 premenopausal women with idiopathic Parkinson's disease recognised an increased severity of their symptoms for a few days before and during menstruation.

Ramsay Hunt syndrome and coeliac disease: a new association?

Two patients with the syndrome of Ramsay Hunt (dyssynergia cerebellaris myoclonica, DCM), associated with malabsorption due to adult coeliac disease, are reported. Both presented with progressive cerebellar ataxia, action myoclonus, and epilepsy. One had gastrointestinal symptoms (recurrent diarrhea and weight loss which responded satisfactorily to a gluten-free diet), but the other did not. In both patients, jejunal biopsy revealed subtotal villous atrophy; serum folate and vitamin E level were also reduced. Neither a gluten-free diet nor vitamin supplements improved the neurological picture. However, some symptomatic relief was afforded by treatment with clonazepam, sodium valproate, carbamazepine, and piracetam. It could be argued that the association between these two disorders is coincidental. However, since we have found this combination in 2 of 14 consecutive cases with DCM, a causal relationship seems likely, although the underlying mechanism remains unknown. Patients with the Ramsay Hunt syndrome should be investigated for malabsorption, and also undergo small intestinal biopsy.

Micturition disturbance in Parkinson's disease

Ten men with longstanding idiopathic Parkinson's disease (IPD) were investigated by urodynamic and electromyographic methods. The urodynamic studies were repeated after stopping anti-Parkinsonian medication for several hours. All patients showed a difference between the two studies, but the changes were unpredictable. Three patients who had high residual urine volumes in both studies were thought to have prostatic obstruction. EMG analysis showed no evidence of a lower motor neurone lesion affecting the striated urethral sphincter. It was concluded that micturition difficulty in the patient with IPD is due to detrusor hyperreflexia, influenced by the basal ganglia, which is not associated with impaired striated urethral sphincter activity.

Lisuride in dystonia

Lisuride hydrogen maleate, 0.4 to 5 (mean, 3) mg/d, was given orally to 42 subjects with various types of dystonia. In seven of the eight patients who improved (one with segmental dystonia, one with myoclonic dystonia, two with spasmodic torticollis, two with cranial dystonia, and two with tardive dystonia), the response was confirmed by double-blind placebo substitution. No patients with a suspected structural brain lesion improved. There was no consistent pattern of response among those patients with different forms of idiopathic (primary) dystonia. Lisuride improved some patients, but had no effect on other, apparently identical, patients.

Anti-parkinsonian drugs today

The drug treatment of Parkinson's disease has progressed through 3 main stages: firstly, the use of anticholinergic drugs and amantadine; then the introduction of levodopa and its association with peripheral decarboxylase inhibitors; and finally the use of direct acting dopamine agonist drugs. Levodopa, however, remains the most effective single drug in Parkinson's disease. Unfortunately, the side effects associated with long term levodopa treatment today constitute an important cause of functional disability. 'Positive' side effects such as involuntary movements and psychiatric disorder remain difficult to manage without causing an increase in Parkinsonian immobility; conversely, management of the 'negative' phenomenon of the 'off' period is limited by these same side effects. This has generated renewed interest in the highly complex pharmacokinetic and pharmacodynamic properties of levodopa, with the aim of reducing fluctuations in plasma levodopa (and hence brain dopamine) concentrations by sustained release oral or continuous parenteral administration of the drug.

Cortical reflex myoclonus responds to intravenous lisuride

Six patients with myoclonus were given 0.1-0.15 mg lisuride i.v. All patients had stimulus-sensitive myoclonus and an increased size of somatosensory evoked potentials, and in three there was electrophysiological evidence of a cortical event time-locked to the jerks. All subjects showed a considerable diminution of spontaneous, action- and stimulus-evoked jerking. Lisuride has potent central dopaminergic and serotonergic actions. Administration of the dopamine agonists levodopa or apomorphine had no effect on myoclonic jerking in any of the six patients. Detailed pharmacological analysis of the myoclonus in one patient showed that levodopa, apomorphine, and haloperidol had no effect, and that haloperidol did not prevent the therapeutic action of lisuride. 5-Hydroxytryptophan abolished the myoclonus, and methysergide prevented the beneficial effect of lisuride, although it did not alter spontaneous myoclonus. These observations suggest that lisuride improves some types of reflex, stimulus-sensitive cortical myoclonus by a serotonin agonist action.

Dopa dose-dependent sexual deviation

Changes in sexual behaviour in patients with Parkinson's disease treated with levodopa are well recognized. Barbeau (1969) was the first to draw attention to “a clear-cut visually evident increase in libido” occurring in at least four out of 62 male parkinsonian patients treated with levodopa. Hyyppa et al (1970) reported that among 41 treated patients 10 experienced an increase of libido. De Ajuriaguerra et al (1972) reported that 29 out of 202 treated patients spontaneously told the authors of their satisfaction in respect of sexual behaviour. They commented “despite a few complaints from their spouses we do not believe there are any grounds to support the hypothesis of hypersexuality, but rather a more or less complete return to normal”. Similarly, Duvoisin and Yahr (1972) found that 8 per cent of a total of 283 patients reported an increase in sexual activity that “generally appeared to represent a partial return towards normalcy”. However, hypersexuality during levodopa therapy in parkinsonian patients was seen in senile dements, or as a feature of a more generalized disturbance, e.g. hypomanic behaviour. The subsequent experience of other authors (Bowers et al, 1971; Shapiro, 1973; Ballivet et al, 1973) has left no doubt that frankly hypersexual behaviour, albeit uncommon, may be provoked by levodopa treatment. Goodwin (1971) reviewed the literature on 908 patients and found an incidence of 0.9 per cent and Shapiro (1973) concurred, with an incidence in the region of 1 per cent of treated patients. Bowers et al (1971) reported 7 out of 19 patients on levodopa who indicated an activation of sexual behaviour on a combined scale of feeling and performance at some time during levodopa therapy. They divided the subjects into three groups: firstly patients who showed increased sexual drive apparently independent of motor improvement, secondly others whose sexual drive increased proportionately with their mobility, and thirdly those who developed hypersexual behaviour as part of an acute brain syndrome with an agitated and confused state.