An acute and long-term study with a dispersible formulation of levodopa/benserazide (Madopar®) in Parkinson's disease

The clinical efficacy, tolerability and administration regimens of a dispersible formulation of levodopa/benserazide (DM) were investigated in 30 patients with idiopathic Parkinson's disease, complicated by motor fluctuations. All 30 patients showed delayed- “on” phenomenon after administration of the first morning dose of standard levodopa (SM), and 20 showed delayed- “on” phenomenon after the first afternoon dose. Patients were receiving standard formulations of levodopa as monotherapy or in combination. A double-dose study of the dispersible vs the standard formulation was performed in 30 patients, 24 of whom participated in a 36-month, follow-up clinical study. In the long-term study, SM was replaced with DM by substituting the first morning dose or the first morning and first afternoon doses. In the double-dose study, mean latency to “on” after the first morning dose was significantly shorter with DM than with SM (p < 0.001), whereas the duration of “on” was similar with the two preparations. The post-prandial delayed- “on” in the 14 patients who responded to therapy was significantly shorter for DM than for SM (p < 0.001). In the long-term study, the mean latency to “on” in all patients was significantly shorter than at baseline (p < 0.001). Time spent in “on” during the active day increased significantly, and remained stable during the 36-month study. No changes were apparent in the mean dosage of levodopa/day or the number of doses/day, and no acute or long-term adverse events were reported. In conclusion, these results confirm the long-term safety of the dispersible formulation, and its improved efficacy compared with standard levodopa formulations, as monotherapy and in association with slow-release formulations.     

The clinical efficacy of single morning doses of levodopa methyl ester: dispersible Madopar and Sinemet plus in Parkinson disease.

For many patients with Parkinson disease and levodopa-related motor fluctuations, the latency to onset of action of a single dose of a levodopa preparation may be both long and variable. In an effort to find a more rapidly acting and reliable preparation of levodopa, we therefore studied the efficacy of single doses of an oral solution of 250 mg of levodopa methyl ester (ME) with benserazide, 50 mg and of a molar equivalent dose of dispersible Madopar (DM) (50/200) in 13 patients in the fasting state after overnight drug withdrawal. The response of seven of these patients was compared to that after two Sinemet 25/100. The latency to "on" was equally fast with ME and DM, and significantly faster than after standard Sinemet. The duration of "on" was similar with all three. Because of this more rapid relief of "off" periods, both ME and DM offer a potential clinical advantage over standard preparations of levodopa.     

Genetic polymorphism of catechol-O-methyltransferase and levodopa pharmacokinetic-pharmacodynamic pattern in patients with Parkinson's disease.

We explored the potential effect of catechol-O-methyltransferase (COMT) genetic polymorphism on the pharmacokinetics and pharmacodynamics of a standard oral dose of levodopa in patients with Parkinson's disease (PD). We prospectively collected blood samples for COMT genotyping from a population of 104 PD patients. Each patient was examined by a standard oral levodopa/benserazide test, based on simultaneous serial measurements of plasma levodopa concentrations, finger-tapping motor effects and dyskinesia ratings, up to 4 hours after dosing. The main levodopa pharmacokinetic outcome variables were time to peak and peak plasma concentration, plasma elimination half-life, and the area under the plasma concentration-time curve. The main outcome levodopa pharmacodynamic variables were latency, duration, and magnitude of the motor effect elicited by the levodopa test dose, the area under the tapping effect-time curve, and the presence of dyskinesias. Nineteen patients (18%) harbored the low-activity homozygous COMT genotype (A/A), 63 patients (61%) carried the intermediate-activity heterozygous COMT genotype (A/G) and 22 patients (21%) had the high-activity homozygous COMT genotype (G/G). The three groups were comparable for vital and clinical characteristics. No significant difference was found in levodopa main pharmacokinetic-pharmacodynamic variables and dyskinesia incidence among the three subgroups of patients. We failed to identify clinically relevant levodopa pharmacokinetic-pharmacodynamic response patterns associated with the COMT polymorphism in PD patients.     

Diurnal motor variations to repeated doses of levodopa in Parkinson's disease

Patients with Parkinson's disease (PD) in long-term levodopa therapy often complain of worsening of motor symptoms in the afternoon and evening. The pathophysiology of this phenomenon is not known. We evaluated the motor response to repeated doses of levodopa during a 12-hour period in 52 parkinsonian patients (19 de novo, 20 stable, and 13 wearing-off). On the day of the study, all patients received standard doses of levodopa/carbidopa at 8:00 a.m., 12:00 noon, and 4:00 p.m. Motor measurements such as tapping test, walking time, and tremor score, and blood samples for levodopa and 3-O-methyldopa (3OMD) plasma analysis, were performed hourly. Mean motor scores and pharmacokinetic data, evaluated for a period of 3 hours after each levodopa dose, were compared. In de novo patients, we did not observe diurnal changes in motor score, whereas a progressive daytime worsening was visible in stable and wearing-off patients. No significant difference in levodopa pharmacokinetics after each levodopa dose was observed within each patient group, whereas 3OMD plasma levels significant increased with repeated levodopa administrations. However, no significant correlation between motor scores and 3OMD plasma levels was observed, suggesting that the diminishing motor response to afternoon and evening doses of levodopa in patients in long-term levodopa therapy does not relate to the pharmacokinetics of the drug. It is possible that this phenomenon may be an expression of the occurrence of tolerance to repeated doses of levodopa.     

Variation in the dopaminergic response during the day in Parkinson disease

OBJECTIVE: In many parkinsonian patients with fluctuating disease the early morning levodopa dose is more effective than the following dose on the same day. In this study we investigated whether the poor responsiveness to the early afternoon dose of levodopa depends only on peripheral and central levodopa pharmacokinetics or also on pharmacodynamic factors. METHODS: Ten parkinsonian patients experiencing postprandial drug-resistant off periods received two boluses of apomorphine by subcutaneous injection at 8 am and 3 pm on two nonconsecutive days. On day 2, therapy was stopped at 11 am. For each bolus we determined time to on, duration of the on state, magnitude of benefit, and levodopa and apomorphine plasma levels at baseline and immediately after patients reached the on state. RESULTS: The mean duration of on phases was significantly shorter and the apomorphine plasma level needed to reach the on state was significantly higher in the afternoon than in the morning (P<0.01 by paired t test). CONCLUSIONS: This study suggest that there is a change in responsiveness to dopaminergic stimulation during the day. The less effective dopaminergic response in afternoon depends on pharmacodynamic factors and not only on peripheral and central levodopa pharmacokinetic.     

Crossover comparison of IPX066 and a standard levodopa formulation in advanced Parkinson's disease

The objective of the study was to compare the pharmacokinetics, motor effects, and safety of IPX066, a novel extended‐release formulation of carbidopa‐levodopa, with an immediate‐release carbidopa‐levodopa formulation in advanced Parkinson's disease. We performed an open‐label crossover study in 27 subjects with advanced Parkinson's disease experiencing motor fluctuations on levodopa therapy. Subjects were randomized 1:1 to 8 days' treatment with either immediate‐release carbidopa‐levodopa followed by IPX066 or IPX066 followed by immediate‐release carbidopa‐levodopa. Pharmacokinetic and motor assessments were undertaken on day 1 for 8 hours (following a single dose) and on day 8 for 12 hours (during multiple‐dose administration). Following a single dose of IPX066 or immediate‐release carbidopa‐levodopa, plasma levodopa concentrations increased at a similarly rapid rate and were sustained above 50% of peak concentration for 4 hours with IPX066 versus 1.4 hours with immediate‐release carbidopa‐levodopa (P < .0001). Multiple‐dose data showed IPX066 substantially reduced variability in plasma levodopa concentrations despite a lower dosing frequency (mean, 3.5 vs 5.4 administrations per day). In addition, total levodopa exposure during IPX066 treatment was approximately 87% higher, whereas the increase in levodopa C_max was approximately 30% compared with immediate‐release carbidopa‐levodopa. Both products were well tolerated. IPX066 provided more sustained plasma levodopa concentrations than immediate‐release carbidopa‐levodopa. Larger, longer‐term, well‐controlled studies should be conducted to provide rigorous assessment of the clinical effects of IPX066. © 2011 Movement Disorder Society     

Pharmacokinetics of etilevodopa compared to levodopa in patients with Parkinson's disease: an open-label, randomized, crossover study

"Dose failures" and "delayed on" phenomena following an intake of levodopa dose in patients with Parkinson's disease (PD) with motor fluctuations may be caused by stagnation of poorly soluble levodopa in the atonic stomach. Etilevodopa is a unique, highly soluble prodrug of levodopa. When ingested, etilevodopa is more readily dissolved in the stomach than levodopa. It passes unchanged through the stomach to the duodenum, where it is rapidly hydrolyzed by local esterases and rapidly absorbed as levodopa. To compare the pharmacokinetics of three different modes of etilevodopa/carbidopa administration with standard levodopa/carbidopa tablets in fluctuating PD patients, 29 patients with PD and response fluctuations were enrolled in an open-label, randomized, four-way crossover study of single doses of 4 treatments: swallowed etilevodopa/carbidopa tablets, etilevodopa/carbidopa tablets dissolved in water, etilevodopa oral solution with carbidopa tablets, and standard levodopa/carbidopa tablets. To measure the maximal concentration (Cmax), time to Cmax (tmax), and area under the curve (AUC) of plasma levodopa, etilevodopa, and carbidopa, blood samples were drawn before drug administration and at intervals up to 240 minutes thereafter. Plasma levodopa tmax was significantly shorter with all three modes of administration of etilevodopa (mean of about 30 minutes) than with levodopa treatment (mean of 54 minutes). During the first 45 minutes after drug ingestion, plasma levodopa AUC was significantly greater after etilevodopa administration than after levodopa administration. Levodopa AUC for 0 to 1 hour and 0 to 2 hours were also significantly greater following administration of etilevodopa/carbidopa swallowed tablets than following administration of levodopa/carbidopa tablets. Mean levodopa Cmax was in the range 2.3 to 2.7 microg/mL for all treatments. Levodopa Cmax was significantly greater following treatment with etilevodopa swallowed tablets than with levodopa tablets. Etilevodopa/carbidopa was well tolerated, with a safety profile comparable to that of levodopa/carbidopa. The shorter levodopa tmax observed with etilevodopa potentially translates to a shorter time to "on". Clinical trials with etilevodopa/carbidopa tablets should be carried out in PD patients with response fluctuations such as "delayed on" and "dose failures".     

Entacapone increases levodopa exposure and reduces plasma levodopa variability when used with Sinemet CR

Entacapone is a catechol-O-methyltransferase (COMT) inhibitor used as an adjunct to levodopa/dopa decarboxylase inhibitors in the treatment of Parkinson's disease. Entacapone increases the bioavailability and reduces the daily variation of plasma levodopa when administered with standard levodopa preparations. These parameters were studied when entacapone was administered with a controlled-release levodopa preparation after repeated administrations throughout the day in 16 healthy male volunteers. On 2 test days, 200 mg entacapone or placebo was administered 4 times during the day at 4-hour intervals concomitantly with a single dose of controlled-release levodopa/carbidopa 100 mg/25 mg (Sinemet CR). Plasma levodopa, 3-O-methyldopa (3-OMD), and carbidopa concentrations were measured before intake of the medication and then every 30 minutes for 16 hours (until midnight), and less frequently up to 24 hours after the first levodopa dose. The minimum, maximum, and average concentration of levodopa; the daily variation of levodopa concentration; and the area under the time concentration curve (AUC) were calculated. The mean (+/-SD) plasma levodopa AUC was 39% (P = 0.0001) higher with entacapone (11,802 +/- 1454 ng/hour/mL) compared with placebo (8465 +/- 927 ng/hour/mL). The daily variation of plasma levodopa was reduced by about 25% with entacapone (P < 0.01). Entacapone significantly reduced plasma 3-OMD concentration by about 50% (P = 0.0001), indicating marked COMT inhibiting activity. There were no differences in plasma carbidopa concentrations. Entacapone significantly increased the bioavailability of levodopa and reduced its daily variation when administered concomitantly with a controlled-release levodopa preparation.     

Kinetic-dynamic relationship of oral levodopa: possible biphasic response after sequential doses in Parkinson's disease.

The potential difference in the concentration-effect relationship of oral sequential doses of levodopa was explored in six Parkinsonian patients with complex fluctuating response. These patients showed "wearing-off phenomena" characterized by a transient worsening of motor function at the end of the first morning dose response to below baseline values and complained of a progressive reduction of levodopa effect during the day. A first standard levodopa dose was given in the morning, after an overnight fast and levodopa withdrawal. A second equal levodopa dose was administered immediately at the end of the first dose deterioration phase. Postimprovement worsening of motor response was also observed after the second levodopa dose in all patients. No significant difference in the pharmacokinetics of levodopa or in duration or magnitude of motor response could be appreciated between the two doses. These results further support the suggestion that, under controlled dietary conditions, plasma levodopa levels and effects relationship is reproducible between doses. Moreover, even when transient deterioration of motor function occurs between levodopa doses, the central dopaminergic system appears to remain responsive to the drug.     

Levodopa pharmacokinetics and motor performance during activities of daily living in patients with Parkinson's disease on individual drug combinations

Pharmacokinetics and pharmacodynamics of levodopa were evaluated at a high-resolution level in a heterogeneous group of 10 patients with idiopathic Parkinson's disease during their normal daily activity. A physician and a nurse spent 10 hours with each patient from the first morning dose of levodopa during daily activities at home and at work. Plasma samples were obtained every 20 minutes for analysis of levodopa and 3-O-methyldopa by high-performance liquid chromatography. To assess clinical response, mobility was rated on every test occasion by patients and by investigators. Food and fluid intake and physical activity were also monitored. There was a large intra- and interindividual variability in the pharmacokinetics of levodopa regardless of the different drug combinations used. Mean plasma levodopa concentration ranged between 0.45 to 7.07 microg/mL and peak concentrations between 0.95 to 13.75 microg/mL. In 44 of 58 dosing events, an oral dose of levodopa was related to a peak in plasma concentration. Assessment of the clinical effects was more sensitive when given by patients than when given by the investigators. The fluctuations of the levodopa concentration in plasma had a clear effect on the clinical parameters assessed, even during early disease stages. Variation in levodopa concentration is the determining factor for motor fluctuations also in patients on clinically optimized combinations with dopamine agonists and enzyme inhibitors.     

Comparison of levodopa with carbidopa, and levodopa with domperidone in Parkinson's disease

In a comparison of the effects of domperidone and carbidopa during levodopa treatment, 20 patients with idiopathic Parkinson's disease were treated with fixed dose regimens of either levodopa 500 mg-domperidone 20 mg or levodopa 100 mg-carbidopa 25 mg; each for 8 weeks. Clinical response, incidence of side effects, and plasma levodopa concentration resulting from each treatment were compared. Overall, in the dosages used, Parkinson's disease was less well controlled with levodopa-domperidone than with levodopa-carbidopa. In eight subjects there was a severe deterioration 2 to 7 days after changing from a fixed dose of levodopa-carbidopa to levodopa-domperidone. In nine subjects who completed the trial, the clinical response, occurrence of dyskinesias and of nausea and vomiting, were similar with both treatments, although peak plasma levodopa concentration and levodopa bioavailability were greater on levodopa-domperidone than on levodopa-carbidopa.     

The subacute levodopa test for evaluating long-duration response in parkinson's disease

The clinical relevance of a long-duration response (LDR) to levodopa therapy in Parkinson's disease (PD) has not been widely recognized. In 25 patients with moderate PD, we measured LDR on motor function after short periods of treatment with levodopa (subacute tests). Each subacute test lasted 15 days and consisted of the oral administration of levodopa at various interdose intervals (IDIs) of 48, 24, 12, 8, 6, and 5 hours. The goal for a subacute test was to achieve a satisfactory antiparkinsonian effect before the last levodopa dose (day 15), i.e., an LDR greater than 50% of the maximal response following an acute levodopa test (LDR-endpoint). Twenty-one patients (84%) reached the LDR-endpoint. The IDI at which levodopa was administered clearly differentiated patients who were otherwise clinically indistinguishable when evaluated at baseline off medication or after an acute levodopa test. The IDI schedule that produced a satisfactory LDR was specific for each patient, since longer IDIs failed to produce the required LDR, and a shorter IDI schedule (resulting in larger cumulative dosage of levodopa) did not significantly enhance the response. Also, the LDR decay rate after discontinuation of treatment was individual for each patient and independent of the cumulative amount of levodopa administered. Both the IDI schedule and the LDR decay rate may reflect the ability of nigrostriatal neurons to store and to release dopamine formed from the exogenous precursor. The assessment of the LDR to levodopa by subacute tests is useful for establishing the appropriate dose of the drug, as well as for developing levodopa sparing strategies in PD patients.     

Combined levodopa-anticholinergic therapy in the treatment of Parkinson's disease. Effect on levodopa bioavailability

The effect of chronic intake of the anticholinergic drug orphenadrine on the bioavailability of levodopa was studied in six patients with Parkinson's disease. Plasma levodopa profiles and corresponding motor response to a standard dose of levodopa plus an inhibitor of peripheral L-aromatic aminoacid decarboxylase (benserazide) were followed, over a 5-h period, on two different sessions, with and without anticholinergic cotherapy. Six control patients were also included in the study for assessment of intrasubject variability in levodopa absorption under identical conditions. A considerable delay in levodopa absorption was found in one patient, and decreased absorption in an additional two patients while on anticholinergic. Patients' clinical performance corresponded well to plasma levodopa profiles. A significant impairment of basal clinical state was observed in two cases on anticholinergic withdrawal, probably as a result of pharmacodynamic interactions. Our observations suggest that chronic anticholinergic intake may contribute to a less predictable pattern of levodopa absorption and related therapeutic response in some subjects.     

Sustained-release of levodopa: single dose study of a new formulation

Summary Motor fluctuations and dyskinesias in Parkinsonian patients may be at least partially due to fluctuations of levodopa plasma concentrations. Sustained-release (SR) formulations of levodopa may present a promising, effective solution of this problem. Therefore we performed a 4-fold, crossover double-blind trial with a new SR preparation, tested in healthy volunteers (Gerlach et al., 1988) before, in 12 Parkinsonian subjects. Two different dosages of the pure new levodopa SR-preparation, a composition of 70% SR and 30% levodopa immediate release (IR) and a conventional IR levodopa preparation were compared by their pharmacokinetic behaviour and their clinical effects. The relative bioavailability of levodopa in plasma was 69% for the combination of SR and IR levodopa release, for the pure SR formulations (100mg levodopa) 54% and (200 mg levodopa) 55%, compared to the 100% of the standard form of IR release of 100 mg levodopa. In contrast to the conventional IR formulation the pharmacokinetic behaviour of the SR preparations showed no initial sharp peak, but more continuous and longer maintaining plasma concentrations of levodopa. Due to the small numbers of cases and the missing homogenity of the selected patients no statistical significant differences between the four preparations regarding the clinical response were observed. But the described pharmacokinetic behaviour gives hope, that these newly developed SR-preparations may lead to progress in the treatment of Parkinson's disease (prolongation of dosage intervals, reduction of motor fluctuations).     

Intermittent vs continuous levodopa administration in patients with advanced Parkinson disease: a clinical and pharmacokinetic study

BACKGROUND: Levodopa-related motor complications can be an important source of disability for patients with advanced Parkinson disease. Current evidence suggests that these motor complications are related to the relatively short half-life of levodopa and its potential to induce pulsatile stimulation of striatal dopamine receptors. Motor complications can be diminished with a continuous infusion of levodopa. OBJECTIVE: To investigate the specific pharmacokinetic changes associated with the benefits of levodopa infusion. DESIGN: We performed an open-label study in 6 patients with Parkinson disease who experienced severe motor complications while receiving standard oral formulations of levodopa/carbidopa. Patients were subsequently treated for 6 months with continuous daytime intraintestinal infusions of levodopa methyl ester. Levodopa pharmacokinetic studies were performed at baseline and 6 months in 3 of these patients. RESULTS: Compared with treatment with intermittent doses of a standard oral formulation of levodopa, continuous infusion provided significant improvement in both "off periods" and dyskinesia. Results of plasma pharmacokinetic studies demonstrated that compared with oral administration, continuous levodopa infusion was associated with a significant increase in the levodopa area under the curve and avoided the low plasma trough levels seen with oral drug administration. CONCLUSIONS: This study confirms that a continuous levodopa infusion is associated with reduced motor complications compared with the standard oral formulation of the drug in patients with advanced PD. Pharmacokinetic studies demonstrate that reduced motor complications are associated with avoiding low plasma levodopa trough levels and are not adversely affected by relatively high plasma levodopa concentrations. We propose that if levodopa/carbidopa could be administered orally in a manner that mirrors the pharmacokinetic pattern of the infusion, it might lead to a similar reduction in motor complications.     

Controlled-release levodopa/carbidopa. I. Sinemet CR3 treatment of response fluctuations in Parkinson's disease

Eight Parkinson patients with response fluctuations completed an open-label trial of a controlled-release carbidopa/levodopa preparation (Sinemet CR3). At the end of 6 weeks, percent "on" time and mean interdose interval increased, the number of daily doses and "off" periods was decreased, and the variability of plasma levodopa levels and disability scores was reduced. However, response fluctuations continued to occur, day-to-day consistency was poor, and the bioavailability of levodopa appeared less than that of standard Sinemet. Overall benefit waned over the next 3 to 6 months. Oral controlled-release carbidopa/levodopa is capable of reducing fluctuations in plasma levodopa levels and clinical performance in Parkinson's disease. The response to this particular controlled-release formulation was suboptimal and unsustained.     

Levodopa and 3-O-methyldopa plasma levels in parkinsonian patients with stable and fluctuating motor response

Many parkinsonian patients with motor fluctuations in response to levodopa show a good response to initial morning doses but fail to respond in the afternoon and evening. We have studied levodopa and 3-O-methyldopa (3-OM-dopa) plasma profiles in 21 patients with fluctuations and eight patients with stable motor function throughout the day. Levodopa plasma peaks and valleys were similar for both group of patients. No significant difference for levodopa absorption index [defined as levodopa plasma levels after each dose divided by the quantity (mg) of ingested levodopa] was found between the first and the second levodopa-carbidopa dose in either group of patients. Even in patients who failed to improve after the second levodopa-carbidopa tablet (p.o.) on the day of the study, no significant variation in levodopa absorption index was observed. 3-OM-dopa values depended mainly upon levodopa consumption and were not different for patients with fluctuating or stable motor response. These findings provide further evidence of the prime role of central pharmacokinetic and pharmacodynamic factors in the pathogenesis of motor fluctuations in Parkinson's disease.     

Controlled release levodopa treatment of motor fluctuations in Parkinson''s disease.

A controlled release preparation of levodopa-carbidopa, CR III, given every 4 hours to 17 Parkinsonian patients for up to 10 months reduced plasma drug variations and improved motor response fluctuations compared with standard levodopa-carbidopa given every 2 hours. The results support the value of pharmaceutical approaches to the stabilisation of circulating levodopa levels in the treatment of Parkinson's disease.     

Sustained-release Madopar HBS® compared with standard Madopar® in the long-term treatment of de novo parkinsonian patients

In this Danish-Norwegian randomized double-blind parallel-group multicentre study, we compared the therapeutic response of slow-release Madopar HBS® to standard Madopar® in 134 de novo patients with idiopathic Parkinson's disease during a 5-year period. The drugs were dosed according to the individual need of the patients. The Webster, NUDS, UPDRS and Hoehn & Yahr scales were used for evaluation of symptoms. Addition of a morning dose of standard Madopar 62.5 mg was allowed after 6 months. Bromocriptine could be administered but not Selegiline. Sixty-five patients got Madopar HBS and 69 standard Madopar. Surprisingly, no differences were found as to the mean daily levodopa dose, the mean number of daily doses or the use of and doses of bromocriptine. Unexpectedly, we found a trend towards a more frequent use of a morning dose of standard Madopar in the group treated with the standard formulation. No differences were observed in the occurrence of motor fluctuations or dyskinesia, the incidence of which was relatively low. Sustained-release Madopar (HBS) thus proved to be as effective as standard Madopar in the long-term treatment of de novo parkinsonian patients, but the drug showed no advantage in postponing or reducing the long-term levodopa treatment problems.     

Entacapone prolongs levodopa response in a one month double blind study in parkinsonian patients with levodopa related fluctuations.

OBJECTIVES--To establish, in a double blind manner, the antiparkinsonian effects of repeated dosing with entacapone, a peripheral COMT inhibitor. METHODS--A one month, cross over study was conducted. During the two four-week treatment periods, entacapone (200 mg) or placebo was given with each levodopa dose four to 10 times daily. Motor responses were repeatedly quantified using the motor part of UPDRS. Plasma levodopa and its metabolites were measured. RESULTS--Entacapone prolonged the availability of levodopa in the plasma and thus to the brain by decreasing its peripheral O-methylation and slowing its elimination rate, without affecting the maximum plasma levodopa concentration or the time to maximum concentration. Corresponding with the pharmacokinetic findings, entacapone prolonged the duration of motor response to an individual levodopa/DDC inhibitor dose by 34 minutes (24%, P = 0.001) and dyskinesiae by 39 minutes (37%, P = 0.002) compared with placebo, without affecting their magnitude or starting time. Entacapone treatment resulted in a reduction of 16% in the mean total daily levodopa dose due to dyskinesiae. Also, according to the home diaries, the mean daily "on" time increased by 2.1 hours compared with placebo, despite the lowered mean levodopa intake. CONCLUSION--The efficacy of repeated entacapone dosing as an adjuvant to levodopa/DDC inhibitor treatment for Parkinson's disease with levodopa related fluctuations is verified.