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PubMed1990

Mortality associated with early and late levodopa therapy initiation in Parkinson's disease.

We evaluated the possible influence of early levodopa treatment on the mortality of Parkinson's disease (PD). One hundred forty-five consecutive parkinsonian patients initiated treatment with levodopa between 1970 and 1983. Ninety-eight of those started levodopa therapy 2 or more years after symptom onset, while 47 received levodopa within the 1st 2 years of the disease. At the end of follow-up, in December 1985, 49 patients had died. Mortality was 2.5 times higher among patients who delayed initiation of levodopa therapy 2 or more years than among those who initiated the therapy earlier. Age and disease severity were the most significant predictors of survival after initiation of levodopa treatment. The risk of death was 10% higher every year of age increase and was 2 and 4 times higher, respectively, for patients at Hoehn and Yahr stages II and III than for patients at Hoehn and Yahr stage I. When we controlled for the effect of age and disease severity on mortality, the cumulative death probability was no longer significantly higher among patients who delayed levodopa treatment than among patients treated within 2 years from disease onset. As far as mortality is concerned, the results show that the time of levodopa treatment initiation during PD has no influence and the drug can be introduced as soon as indicated by the severity of the disease progression.

Female↗
PubMed1993

Pharmacodynamic modeling of oral levodopa: clinical application in Parkinson's disease.

We investigated the relationship between levodopa plasma concentration and the tapping effect, after a standard oral levodopa test, by kinetic-dynamic modeling in 40 parkinsonian patients with stable or fluctuating response to levodopa, and found no difference in levodopa plasma pharmacokinetics between stable and fluctuating patients. Conversely, levodopa equilibration half-life between plasma and effect-site concentration was five-fold shorter on average in fluctuating patients. Overall, levodopa equilibration half-life highly correlated with the duration of tapping response and provided a reliable quantitative index of central mechanisms that affect the length of clinical effect. Individual fitting of tapping measures to modeled drug effect-site concentrations by sigmoid Emax model revealed that fluctuating patients required almost two-fold higher levodopa concentrations (EC50) to elicit almost the same motor response (Emax). These findings suggest that shortening of levodopa clinical effect may be accompanied by a reduced drug affinity for the nigrostriatal dopaminergic system (EC50), with no change in its intrinsic activity (Emax).

Administration, Oral↗
PubMed1994

Effect of plasma levels of large neutral amino acids and degree of parkinsonism on the blood-to-brain transport of levodopa in naive and MPTP parkinsonian monkeys.

We investigated the transport of levodopa from blood to brain in control and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) parkinsonian monkeys by using intracerebral microdialysis. The degree of parkinsonism was established by the monkey's clinical score and its postmortem striatal dopamine level. We administered levodopa plus carbidopa either orally or by intravenous injection. We estimated the blood-to-brain transport of levodopa as the ratio of its concentration in the brain's extracellular fluid to that in arterial plasma. This ratio was reduced in the MPTP parkinsonian monkeys, and we found an inverse relationship between the monkeys' ability to transport levodopa from blood to brain and their degree of parkinsonism. The oral administration of a high-protein meal or the intravenous infusion of large neutral amino acids before the administration of the levodopa plus carbidopa reduced the transport of levodopa into the brain, as measured by microdialysate collected from the striatum. We found that in two animals an intraperitoneal injection of the beta-adrenergic agonist isoproterenol increased the blood-to-brain transport of levodopa. Pharmacologic manipulation of the transport of levodopa from blood to brain may offer a new strategy for the treatment of Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2001

Interactions between deep brain stimulation and levodopa in Parkinson's disease.

OBJECTIVE: To quantify the effects of deep brain stimulation (DBS) of globus pallidus interna (GPi) and subthalamic nucleus (STN) on motor fluctuations and dyskinesia in PD and to determine how the response to levodopa was modified by DBS. BACKGROUND: Patients report that DBS reduces levodopa-induced motor fluctuations and dyskinesia throughout the day, but this has not been objectively measured. Further, the means by which DBS alters the response to levodopa to improve motor fluctuations is unknown. METHODS: Twelve subjects, six with bilateral GPi electrodes and six with bilateral STN electrodes, were studied 12 to 33 months after surgery. To quantify motor fluctuations and dyskinesia, subjects were monitored hourly throughout 2 waking days with their usual oral medications, 1 day with DBS on and 1 day with DBS off, with subjects and nurse raters blinded to DBS status. To examine the effects of DBS on levodopa pharmacodynamics, the effects of a 2-hour levodopa infusion were examined, 1 day with DBS on and 1 day with DBS off, again under double-blind conditions. Time course of variations in parkinsonism was evaluated by tapping speed, arising and walking speed, tremor scores, and dyskinesia scores. RESULTS: DBS raised the mean tapping speed and reduced the coefficient of variation during the waking day. This was achieved by increasing the lowest or trough tapping speed between doses of antiparkinson medications. Mean walking speed was modestly increased and mean tremor scores were reduced. DBS increased the drug-off tapping speed, but neither the peak response nor the duration of response to levodopa was affected by DBS. The study was not powered to detect differences between GPi and STN stimulation and the only difference that approached significance was that GPi reduced peak dyskinesia and STN tended to increase peak dyskinesia. CONCLUSION: DBS objectively reduces motor fluctuations. This is achieved by reduction of drug-off disability and not by alterations in levodopa pharmacodynamics. This finding suggests alleviation of interdose trough disability as an alternative strategy to prolonging the effects of each dose of levodopa as a means to reduce motor fluctuations.

Adult↗
PubMed1999

Maximizing the benefit:risk ratio of levodopa therapy in Parkinson's disease.

For over 30 years, levodopa has been the gold standard for managing the symptoms of Parkinson's disease. Treatment with levodopa has resulted in a marked decrease in disease-associated mortality and morbidity. However, one of its drawbacks is that many patients experience a shorter duration of response and increased motor fluctuations with disease progression and long-term levodopa therapy. These increased motor fluctuations, including dyskinesias, may be the consequence of oxidative stress or inability to store and regulate intrasynaptic dopamine concentrations with disease progression. Clinical investigations have demonstrated that continuous dopaminergic stimulation may widen the therapeutic window for levodopa and improve motor fluctuations. Strategies for providing continuous dopaminergic replacement include administration of levodopa by continuous infusion, controlled-release levodopa, long-acting dopamine agonists, and inhibitors of levodopa metabolism. The catechol-O-methyltransferase inhibitors that block a compensatory metabolic pathway for levodopa and prolong its duration may improve the consistency of the dopaminergic response.

Antiparkinson Agents↗
PubMed1999

Interventions to achieve tonic exposure to levodopa: delaying or preventing the onset of motor complications.

Variations in levodopa delivery and subsequent dopamine exposure may lead to motor fluctuations and dyskinesias in patients with Parkinson's disease, as the therapeutic window for levodopa narrows with disease progression. Long-term exposure to the oscillations in levodopa-derived dopamine also is suggested to cause postsynaptic changes within the dopaminergic system, leading to further reductions in the drug's efficacy. The need to extend the actions of levodopa led to the development of the catechol-O-methyltransferase (COMT) inhibitors, which are the newest agents introduced to manage the symptoms of Parkinson's disease. Entacapone and tolcapone are two potent, selective, and reversible COMT inhibitors that effectively augment levodopa's pharmacokinetics by increasing area under the plasma concentration versus time curve and plasma elimination half-life without significantly affecting peak levodopa concentrations. This enhanced pharmacokinetic effect results in marked improvements in patients' clinical response. In patients experiencing end-of-dose wearing-off, the addition of either entacapone or tolcapone led to improvements in "on" time, "off" time, and the Unified Parkinson's Disease Rating Scale scoring system, even though many patients already were receiving optimum dosages of various other antiparkinsonian drugs. In patients with stable responses to long-term levodopa, addition of tolcapone significantly reduced the onset of motor fluctuations. These data, combined with the potential for delaying the onset of motor fluctuations, suggest that COMT inhibition may enhance levodopa's short- and long-term efficacy.

Antiparkinson Agents↗
PubMed2003

Levodopa-induced response fluctuations in patients with Parkinson's disease: strategies for management.

Fluctuations in response to levodopa in patients in the advanced stages of idiopathic Parkinson's disease occur frequently and are a difficult problem to treat. Patients who are treated with levodopa have an additional 10% risk of experiencing response fluctuations with each year of treatment: 50% of patients have this problem after 5 years of receiving levodopa therapy and almost 100% of patients after 10 years. The mechanisms by which response fluctuations occur are only partially understood and can be divided into three main types: (i) presynaptic neuronal degeneration leading to a lack of buffering of released levodopa, which is mainly related to wearing-off phenomena; (ii) postsynaptic changes in dopamine receptor sensitivity and number, partially caused by the presynaptic changes, which are clinically related to at-random response fluctuations; and (iii) pharmacokinetic and pharmacodynamic influences of exogenously administered dopaminergic agents. Several oral and parenteral treatment strategies are recommended to manage response fluctuations, such as optimisation of dopamine receptor agonist therapy in combination with a reduction of the levodopa load; use of slow-release levodopa formulations; use of catechol-O-methyltransferase inhibitors; an increase of levodopa dose frequency; use of high-dose amantadine; and intermittent or continuous use of apomorphine and/or levodopa. Continuous stimulation of dopamine receptors with dopaminergic agents is one of the crucial basic steps in the treatment of patients at an advanced stage of Parkinson's disease, and the preferential use of dopamine receptor agonists has proven to be successful in the prevention and treatment of response fluctuations.

Age Factors↗
PubMed1999

[Levodopa-induced psychosis in patients with idiopathic Parkinson disease].

BACKGROUND: To identify which clinical factors can modify the probability of the appearance of the psychotic syndromes in patients with idiopathic Parkinson's disease treated with levodopa. PATIENTS AND METHODS: 214 patients were retrospectively studied to evaluate the appearance of hallucinosis, delusions or mental confusion, from the beginning of the treatment with levodopa to a transversal evaluation along the course of the disease. To determine which clinical factors were independent predictors of psychosis, a multivariate logistic regression model was obtained, using the variables for which the univariate studies showed p values under 0.25. RESULTS: The multivariate model showed that the probability of developing psychosis during levodopa treatment was higher for the patients with intermediate or advanced stages of the disease (Hoehn and Yarh scale), at the beginning of the treatment (OR: 4.5; 95% CI: 1.86-11.23), when amantadine was administrated as associated drug (OR: 3.31; 95% CI: 1.19-9.23) and for the patients who presented motor fluctuations (OR: 3.08; 95% CI: 1.32-7.16). Univariate studies showed a significant association between levodopa psychosis and dyskinesias (univariate OR: 2.44; 95% CI: 1.12-5.33). Patients who suffered from psychotic complications had received significantly higher mean levodopa daily dose (p = 0.016) and the punctuation reached in the Folstein's Mini-Mental Scale was significantly lower (p = 0.0001). CONCLUSIONS: Levodopa psychosis appears in a "bad prognostic" group of patients, characterized by a greater motor and cognitive impairment and by the occurrence of other levodopa central adverse effects, higher doses of levodopa and a more frequent administration of other antiparkinsonian drugs.

Aged↗
PubMed2000

Pulsatile stimulation of dopamine receptors and levodopa-induced motor complications in Parkinson's disease: implications for the early use of COMT inhibitors.

Increasing laboratory and clinical evidence indicates that pulsatile stimulation of dopamine receptors contributes to the development of levodopa-related motor complications in PD. In keeping with this concept, clinical trials have demonstrated that initiating therapy with a long-acting dopamine agonist reduces the risk of inducing motor complications in comparison to levodopa. However, the introduction of levodopa is associated with the development of motor complications even in the presence of a long-acting dopamine agonist in both PD patients or MPTP treated monkeys. Administration of levodopa with a catechol-O-methyl transferase (COMT) inhibitor increases its plasma half-life, smoothes out peaks and troughs, and delivers levodopa to the brain in a more continuous fashion. We hypothesize that the risk of developing motor complications in PD patients when levodopa is introduced can be reduced if the levodopa is coupled with a COMT inhibitor so as to provide more continuous dopaminergic stimulation of dopamine receptors. A proposed algorithm for the treatment of the early PD patient is to initiate therapy with a dopamine agonist, and supplement with levodopa coupled with a COMT inhibitor when the dopamine agonist cannot provide satisfactory clinical benefits.

Catechol O-Methyltransferase Inhibitors↗
PubMed2004

[Influence of levodopa on cognition of idiopathic Parkinson's disease].

INTRODUCTION: Idiopathic Parkinson's disease induces alterations both motor and cognitive. Levodopa, the treatment of choice, offers initial improvement, but causes long term important complications. It is ignored if it provokes or not a similar situation in cognitive function. METHOD: Two groups of idiopathic parkinsonian patients were studied. One of them was using levodopa as a regular treatment, the other had de novo patients. A group of healthy controls was also studied. The levodopa group was evaluated when levodopa plasma concentration was maximum and when it was minimum. A cognitive battery was used in order to assess the cognitive status of all subjects. RESULTS: Significant differences between the two groups of patients and the healthy controls were found when the treated group had a maximum plasmatic concentration of levodopa. There were also significant differences when they had a minimum concentration in comparison with the healthy controls. The performances of the patients taking levodopa varied between both conditions. CONCLUSIONS: Parkinson's disease provokes a wide variety of cognitive alterations, therefore basal ganglia can be related to a more general function as learning and storing cognitive and motor programs. Levodopa influences in a different way different cognitive functions differently and its influence varies between highest and lowest plasmatic concentrations periods. These results allow us to draw important conclusions about the cognitive alterations caused by the natural course of Parkinson's disease, the introduction of treatment with levodopa and the relationship between basal ganglia and human cognition.

Antiparkinson Agents↗
PubMed2000

Levodopa in plasma correlates with body weight of parkinsonian patients.

Background: Antiparkinsonian comedication and/or altered gastrointestinal motility and absorption influence plasma levels of levodopa. Another putative factor may represent body weight. The objective of our study was to examine the relationship between body weight and levodopa in plasma of parkinsonian patients.Methods: We enrolled 26 individuals into this trial on the resorption of levodopa. A standardized protocol was used, which eliminated influencing factors, such as comedication, activity, food and estimated levodopa plasma levels at fixed timepoints.Results: Levodopa amount (Spearman R=-0.48; p=0.013) and maximum concentration (Spearman R=-0.50; p=0.008) in plasma correlated negatively with body weight.Conclusion: Doses of levodopa should be considered in relation to body weight. Thus severe loss of weight may reduce the need for oral levodopa intake by parkinsonian subjects and may represent a putative factor in the occurrence of dyskineasia in these patients unless there is a concomitant reduction in the dose of oral levodopa.

Journal Article↗
PubMed1971

Levodopa in Parkinsonism: the effects of withdrawal of anticholinergic drugs.

The results are reported of a trial in which 34 patients receiving a stable dose of levodopa for the treatment of idiopathic Parkinsonism, as well as anticholinergic drugs which they had been taking before the introduction of levodopa, underwent withdrawal of their anticholinergic remedies. Withdrawal was gradual over four weeks in 17 patients (group 1) and abrupt in the remaining 17 (group 2).Only 11 out of 34 patients on stable levodopa therapy were able to tolerate withdrawal of anticholinergic drugs for more than eight weeks. The main reasons for the resumption of these remedies were subjective increases in slowness in 20 (59%), tremor in 15 (44%), and recurrence of hypersalivation in 5 (15%). Hypersalivation was the single feature which was most significantly and adversely influenced by anticholinergic withdrawal in patients on levodopa irrespective of whether withdrawal was sudden or gradual. It is suggested that the synergism which seems to exist between anticholinergic remedies and levodopa may be due to inhibition of dopamine inactivation by anticholinergic drugs, thus ensuring continual utilization, or alternatively, to a primary central anticholinergic effect.Objective and more severe subjective deterioration occurred only on sudden withdrawal. Hence we would advise that if for any reason anticholinergic drugs are to be withdrawn in patients receiving a stable dosage of levodopa this must be done slowly. Conversely it would appear from our results that the introduction of anticholinergic drugs in patients treated initially with levodopa is likely to produce additional benefit, particularly when the maximum tolerated dose of levodopa is small.

Dihydroxyphenylalanine↗
PubMed2001

Induction by dopamine D1 receptor agonist ABT-431 of dyskinesia similar to levodopa in patients with Parkinson disease.

BACKGROUND: Dyskinesias are a frequent adverse effect of long-term levodopa therapy. The relative contribution of dopamine D(1) and D(2) receptor function to the pathophysiology of levodopa-induced dyskinesias remains a matter of controversy. OBJECTIVE: To establish whether a selective D(1) dopamine agonist induces more or less dyskinesia than levodopa in primed dyskinetic patients with Parkinson disease. METHODS: We studied ABT-431, the prodrug of a fully selective D(1) agonist, in 20 subjects with advanced Parkinson disease and a fluctuating response to levodopa complicated by dyskinesias. Eight patients were studied in a double-blind, randomized design (French centers); 12, in an open, randomized design (US centers). We assessed and compared the antiparkinsonian (Unified Parkinson's Disease Rating Scale) and dyskinetic (response induced by an acute challenge of a suprathreshold dose of levodopa and by 4 different ascending doses (5, 10, 20, and 40 mg) of ABT-431 during the 6 hours after the challenge. RESULTS: The separate analysis of the double-blind and open data led to the same findings, ie, the antiparkinsonian and dyskinetic responses induced by ABT-431 were dose related. At the most effective doses (20 and 40 mg), ABT-431 exhibited similar antiparkinsonian benefit and produced similar dyskinesias as levodopa. CONCLUSION: Dopamine D(1) agonists can induce a full antiparkinsonian response but do not support previous hypotheses suggesting that D(1) agonists are more or less likely to produce dyskinesias than levodopa.

Adult↗
PubMed2004

Double-blind, placebo-controlled study of entacapone in levodopa-treated patients with stable Parkinson disease.

BACKGROUND: The catechol O-methyltransferase inhibitor entacapone acts by extending the elimination half-life of levodopa and is currently approved as an adjunct to levodopa for the treatment of patients with Parkinson disease (PD) with motor fluctuations. OBJECTIVE: To determine if the addition of entacapone administration provides benefit to levodopa-treated PD patients who have a stable response to levodopa and do not experience motor complications. DESIGN: Prospective, double-blind, placebo-controlled trial. SETTING: Outpatient multicenter study. PATIENTS: Female and male patients 30 years or older with idiopathic PD receiving stable doses of levodopa or carbidopa with or without other dopaminergic therapies and who did not experience motor fluctuations were eligible for the study. MAIN OUTCOME MEASURES: Parkinsonian function and quality of life. RESULTS: The addition of entacapone did not improve motor scores on the Unified Parkinson's Disease Rating Scale in levodopa-treated PD patients who did not experience motor fluctuations. The mean +/- SE adjusted change between baseline and final treatment visit was -0.9 +/- 0.35 in the entacapone group and -0.8 +/- 0.35 in the placebo group (P = .83). Significant improvement with entacapone treatment was detected in several quality-of-life measures, including the Parkinson Disease Questionnaire 39, the 36-item Short-Form Health Survey, the Parkinson's Symptom Inventory, and investigator and subject Clinical Global Assessments. The drug was well tolerated by patients in this population. CONCLUSIONS: The catechol O-methyltransferase inhibitor entacapone, used as an adjunct to levodopa in PD patients who do not experience motor fluctuations, does not improve Unified Parkinson's Disease Rating Scale motor scores but does improve a variety of quality-of-life measures.

Aged↗
PubMed2002

Dopamine transporter brain imaging to assess the effects of pramipexole vs levodopa on Parkinson disease progression.

CONTEXT: Pramipexole and levodopa are effective medications to treat motor symptoms of early Parkinson disease (PD). In vitro and animal studies suggest that pramipexole may protect and that levodopa may either protect or damage dopamine neurons. Neuroimaging offers the potential of an objective biomarker of dopamine neuron degeneration in PD patients. OBJECTIVE: To compare rates of dopamine neuron degeneration after initial treatment with pramipexole or levodopa in early PD by means of dopamine transporter imaging using single-photon emission computed tomography (SPECT) with 2beta-carboxymethoxy-3beta(4-iodophenyl)tropane (beta-CIT) labeled with iodine 123. DESIGN: Substudy of a parallel-group, double-blind randomized clinical trial. SETTING AND PATIENTS: Eighty-two patients with early PD who were recruited at 17 clinical sites in the United States and Canada and required dopaminergic therapy to treat emerging disability, enrolled between November 1996 and August 1997. INTERVENTIONS: Patients were randomly assigned to receive pramipexole, 0.5 mg 3 times per day with levodopa placebo (n = 42), or carbidopa/levodopa, 25/100 mg 3 times per day with pramipexole placebo (n = 40). For patients with residual disability, the dosage was escalated during the first 10 weeks, and subsequently, open-label levodopa could be added. After 24 months of follow-up, the dosage of study drug could be further modified. MAIN OUTCOME MEASURES: The primary outcome variable was the percentage change from baseline in striatal [(123)I]beta-CIT uptake after 46 months. The percentage changes and absolute changes in striatal, putamen, and caudate [(123)I]beta-CIT uptake after 22 and 34 months were also assessed. Clinical severity of PD was assessed using the Unified Parkinson Disease Rating Scale (UPDRS) 12 hours off anti-PD medications. RESULTS: Sequential SPECT imaging showed a decline in mean (SD) [(123)I]beta-CIT striatal uptake from baseline of 10.3% (9.8%) at 22 months, 15.3% (12.8%) at 34 months, and 20.7% (14.4%) at 46 months-approximately 5.2% per year. The mean (SD) percentage loss in striatal [(123)I]beta-CIT uptake from baseline was significantly reduced in the pramipexole group compared with the levodopa group: 7.1% (9.0%) vs 13.5% (9.6%) at 22 months (P =.004); 10.9% (11.8%) vs 19.6% (12.4%) at 34 months (P =.009); and 16.0% (13.3%) vs 25.5% (14.1%) at 46 months (P =.01). The percentage loss from baseline in striatal [(123)I]beta-CIT uptake was correlated with the change from baseline in UPDRS at the 46-month evaluation (r = - 0.40; P =.001). CONCLUSIONS: Patients initially treated with pramipexole demonstrated a reduction in loss of striatal [(123)I]beta-CIT uptake, a marker of dopamine neuron degeneration, compared with those initially treated with levodopa, during a 46-month period. These imaging data highlight the need to further compare imaging and clinical end points of PD progression in long-term studies.

Aged↗
PubMed2001

Cabergoline for levodopa-induced complications in Parkinson's disease.

BACKGROUND: Long term levodopa therapy in Parkinson's disease is associated with the development of motor complications including abnormal involuntary movements and a shortening response to each dose (wearing off phenomenon). It is thought that dopamine agonists can reduce the duration of immobile off periods and the need for levodopa therapy whilst maintaining or improving motor impairments and only minimally increasing dopaminergic adverse events. OBJECTIVES: To compare the efficacy and safety of adjuvant cabergoline therapy versus placebo in patients with Parkinson's disease, already established on levodopa and suffering from motor complications. SEARCH STRATEGY: Electronic searches of MEDLINE, EMBASE and the Cochrane Controlled Trials Register. Handsearching of the neurology literature as part of the Cochrane Movement Disorders Group's strategy. Examination of the reference lists of identified studies and other reviews. Contact with Pharmacia Upjohn Limited. SELECTION CRITERIA: Randomised controlled trials of cabergoline versus placebo in patients with a clinical diagnosis of idiopathic Parkinson's disease and long-term complications of levodopa therapy. DATA COLLECTION AND ANALYSIS: Data was abstracted independently by the authors and differences settled by discussion. The outcome measures used included Parkinson's disease rating scales, levodopa dosage, off time measurements and the frequency of withdrawals and adverse events. MAIN RESULTS: Cabergoline has been compared with placebo in two phase II (6 - 12 weeks) and one phase III randomised controlled trials (24 weeks). These were double-blind, parallel group, multicentre studies including 268 patients with Parkinson's disease and motor complications. The reduction of 1.14 hours (WMD; 95% CI -0.06, 2.33; p = 0.06) in off time in favour of cabergoline was not statistically significant. Inadequate data on dyskinesia was collected either on rating scales or as adverse event reporting to allow a conclusion to be drawn. A small but statistically significant advantage of cabergoline over placebo was seen in one study for UPDRS ADL (part II) score and UPDRS motor score. No such advantage was seen in one other study due to small numbers of patients and the comparatively low doses of cabergoline used. No significant differences in Schwab and England scale were seen in two studies. Levodopa dose reduction was significantly greater with cabergoline (WMD 149.6 mg/d; 95% CI 94.1, 205.1; p < 0.00001). There was a trend towards more dopaminergic adverse events with cabergoline but this did not reach statistical significance at the p < 0.01 level. However, there was a trend towards fewer withdrawals from cabergoline. REVIEWER'S CONCLUSIONS: In the management of the motor complications seen in Parkinson's disease, cabergoline can be used to reduce levodopa dose and modestly improve motor impairment and disability with an acceptable adverse event profile. These conclusions are based on, at best, medium term evidence.

Antiparkinson Agents↗
PubMed2001

Cabergoline versus bromocriptine for levodopa-induced complications in Parkinson's disease.

BACKGROUND: Long term levodopa therapy in Parkinson's disease is associated with the development of motor complications including abnormal involuntary movements and a shortening response to each dose (wearing off phenomenon). It is thought that dopamine agonists can reduce the duration of immobile off periods and the need for levodopa therapy whilst maintaining or improving motor impairments and only minimally increasing dopaminergic adverse events. OBJECTIVES: To compare the efficacy and safety of adjuvant cabergoline therapy versus bromocriptine in patients with Parkinson's disease, already established on levodopa and suffering from motor complications. SEARCH STRATEGY: Electronic searches of MEDLINE, EMBASE and the Cochrane Controlled Trials Register. Handsearching of the neurology literature as part of the Cochrane Movement Disorders Group's strategy. Examination of the reference lists of identified studies and other reviews. Contact with Pharmacia Upjohn Limited. SELECTION CRITERIA: Randomised controlled trials of cabergoline versus bromocriptine in patients with a clinical diagnosis of idiopathic Parkinson's disease and long-term complications of levodopa therapy. DATA COLLECTION AND ANALYSIS: Data were abstracted independently by the authors and differences settled by discussion. The outcome measures used included Parkinson's disease rating scales, levodopa dosage, off time measurements and the frequency of withdrawals and adverse events. MAIN RESULTS: Cabergoline has been compared with bromocriptine in five randomised, double-blind, parallel group studies including 1071 patients. Only one of the phase II studies was medium term (36 weeks), the others all being short term (12 -15 weeks). The non-significant difference in off time reduction produced by cabergoline compared with bromocriptine was 0.29 hours/day in favour of the former (weighted mean difference; 95% CI -0.10, 0.68; p = 0.15). Dyskinesia reported as an adverse event was significantly increased with cabergoline compared with bromocriptine (Peto odds ratio 1.57; 95% CI 1.05, 2.35; p = 0.03). Motor impairment and disability were measured in four of the studies using the UPDRS rating scale but the small differences in UPDRS ADL (part II) and motor (part III) scores were not statistically significant in any study. Similarly, no significant difference in Schwab and England score was seen. The number of patients rated as much or very much improved on a clinician's global impression scale was similar with both agonists. Levodopa dose reduction was no different between cabergoline and bromocriptine. There was more confusion with cabergoline (Peto odds ratio 2.02; 95% CI 1.09, 3.76; p = 0.03). Otherwise, dopaminergic adverse events were comparable with these agonists and no significant difference in all cause withdrawal rate was found. REVIEWER'S CONCLUSIONS: Cabergoline produces similar benefits to bromocriptine in off time reduction, motor impairment and disability ratings, and levodopa dose reduction over the first three months of therapy. Dyskinesia and confusion were increased with cabergoline but otherwise the frequency of adverse events and withdrawals from treatment were similar with the two agonists.

Antiparkinson Agents↗
PubMed2004

Catechol-O-methyltransferase inhibitors versus active comparators for levodopa-induced complications in Parkinson's disease.

BACKGROUND: As Parkinson's disease progresses the control of the symptoms often requires the addition of other drugs to levodopa. The principle aim of COMT inhibitor therapy is to increase the duration of effect of the levodopa dose and thus reduce the time patients spend in the relatively immobile 'off' phase. OBJECTIVES: To compare the efficacy and safety of adjuvant COMT inhibitor therapy versus active comparators in patients with Parkinson's disease, already established on levodopa and suffering from motor complications. SEARCH STRATEGY: Electronic searches of the Cochrane Controlled Trials Register (The Cochrane Library Issue 1, 2003), MEDLINE (1966-2003), EMBASE (1974-2003), were conducted. Grey literature was hand searched and the reference lists of identified studies and reviews examined. The manufacturers of COMT inhibitors were contacted. SELECTION CRITERIA: Randomised controlled trials of adjuvant COMT inhibitor therapy versus an active comparator in patients with a clinical diagnosis of idiopathic Parkinson's disease and long-term complications of levodopa therapy. DATA COLLECTION AND ANALYSIS: Data was abstracted independently by the authors and differences settled by discussion. The outcome measures used included Parkinson's disease rating scales, levodopa dosage, 'off' time measurements and the frequency of withdrawals and adverse events. MAIN RESULTS: Two trials were found that examined the efficacy of a COMT inhibitor against an active comparator (n = 349). Koller 1998 compared the efficacy of tolcapone versus pergolide (n = 203) over 12 weeks and TSG 1999 compared the efficacy of tolcapone versus bromocriptine (n = 146) over 8 weeks. No trials were found that compared entacapone with active comparators. Tolcapone produced similar benefits to bromocriptine in 'off' time reduction, motor impairment and disability ratings over three months of therapy. Tolcapone produced a greater reduction in levodopa dosage than bromocriptine. Tolcapone produced similar benefits to pergolide in levodopa dose reduction, motor impairment and disability ratings, and in generic health-related quality of life scales over the first two months of therapy. Tolcapone produced a greater improvement in the disease-specific quality of life scale PDQ-39 than pergolide. Nausea, constipation and orthostatic complaints were greater with agonist therapy, but otherwise the frequency of adverse events and withdrawals from treatment were similar with the two classes of adjuvant medication. One patient had significantly elevated liver enzymes whilst on tolcapone, but otherwise the frequency of adverse events and withdrawals from treatment were similar. REVIEWERS' CONCLUSIONS: The two trials comparing tolcapone with the dopamine agonists bromocriptine and pergolide were underpowered to detect clinically relevant differences between them. This is based on medium-term evidence. No evidence was found comparing entacapone with active comparators. Further larger and longer-term trials are required to compare tolcapone with entacapone and COMT inhibitor therapy with alternative adjuvant classes of drug in later Parkinson's disease such as dopamine agonists and monoamine oxidase inhibitors.

Antiparkinson Agents↗