The long-acting dopamine receptor agonist cabergoline in early Parkinson's disease: final results of a 5-year, double-blind, levodopa-controlled study. Double-blind study of the activity and tolerability of cabergoline versus placebo in parkinsonians with motor fluctuations.
Cabergoline is an ergoline derivative with a very long half-life that allows once-daily administration and the potential for more continuous stimulation of dopaminergic receptors than is possible with other dopamine receptor agonists (DAs). The aim of this study was to evaluate whether the possible advantage resulting from a more sustained dopaminergic effect of cabergoline would translate into delayed onset of motor complications, compared with levodopa, in patients with newly diagnosed Parkinson's disease.
                This study was a double-blind, multicentre trial that compared cabergoline and levodopa as initial therapy for Parkinson's disease. A total of 419 levodopa-, DA- and selegiline-naive patients with newly diagnosed Parkinson's disease were randomised to receive either cabergoline (n = 211) or levodopa (n = 209). Treatment was titrated to an optimal dose over a period of up to 24 weeks and then continued at this dose until the study endpoint (confirmed motor complications) or up to a maximum of 5 years. At years 1-5, the cabergoline group was receiving cabergoline at average daily doses ranging from 2.8-2.9 mg, with added levodopa at mean daily doses ranging from 322 mg at year 1 to 431 mg at year 5; over the same period, the levodopa group was receiving daily levodopa doses of 784 mg. Thus, patients in the cabergoline group received <50% levodopa than patients in the levodopa group.
                Motor complications were significantly delayed (p = 0.0175) and occurred less frequently in cabergoline-treated patients than in levodopa-treated patients (22.3% vs 33.7%). Cox model proportional hazards regression analysis showed that the relative risk of developing such complications was >50% lower (0.46; p < 0.001) in the cabergoline group compared with the levodopa group. In particular, development of dyskinesias was markedly delayed in the cabergoline group and occurred in 9.5% of patients compared with 21.2% in the levodopa group (p < 0.001). Among patients not requiring supplemental levodopa, the frequency of motor complications was three times higher with levodopa (15.5% of 110 patients) than with cabergoline (5.3% of 76 patients). Among patients who did need supplemental levodopa, motor complications were more frequent in the levodopa arm (54.1% of 98 patients) than in the cabergoline arm (31.9% of 135 patients). Consistent improvements relative to baseline in average Unified Parkinson's Disease Rating Scale (UPDRS) daily living activities and motor function sections, and in Clinical Global Impression severity of illness and physician- and patient- rated global improvement scores, were seen in both treatment groups, with maximal effects occurring within 2 years. However, levodopa treatment was associated with a significantly (p < 0.001) greater improvement in motor disability (as measured by the UPDRS motor score) over time, with mean values of 13.8 versus 12.9 in the cabergoline versus levodopa arm recorded at 1 year, 18.6 versus 17.2 at 3 years and 19.2 versus 16.3 at 5 years, respectively. While the overall frequency of adverse events was similar in the two groups, the cabergoline-treated group experienced marginally, but not significantly, higher frequencies of nausea, vomiting, dyspepsia and gastritis (37.4% vs 32.2% in the levodopa group) and of dizziness and postural hypotension (31.3% vs 24% in the levodopa group). Cabergoline-treated patients also experienced a significantly higher frequency of peripheral oedema (16.1% vs 3.4%, respectively; p < 0.0001). The cabergoline and levodopa groups had similar rates of sleepiness (17.5% vs 18.3%, respectively) and hallucinations (4.8% vs 4.4%, respectively); in an elderly population subset, hallucinations were reported in 7.1% and 6.5% of patients taking cabergoline and levodopa, respectively. Adverse events generally occurred more frequently in female patients (with the exception of dyskinesias, hyperkinesias and hallucinations, which occurred more frequently in men) and in the elderly.
                This study showed that, compared with levodopa, initial therapy with cabergoline in patients with Parkinson's disease is associated with a lower risk of response fluctuations at the cost of a marginally reduced symptomatic improvement and some tolerability disadvantages that are mostly limited to a significantly higher frequency of peripheral oedema. The use of a dopamine agonist with a long duration of action has theoretical advantages in attempting to reduce the motor fluctuations in Parkinson's disease. We report the results of a double-blind controlled study of adding cabergoline, an ergot derivative with potent long-lasting high affinity for the D2 receptor, to levodopa therapy in 37 patients with severe fluctuations in response to treatment. Increasing dosages of cabergoline (19 patients) or placebo (18 patients) were added to each patient's stable levodopa regime. The two patient groups were similar at baseline in terms of age, disease duration, duration of levodopa treatment, and average hours "off" per day. Following incremental dose titration, patients in the cabergoline group had a significant reduction in hours "off" per day from 5.0 (SD 2.1) to 3.0 (SD 2.5), but there was no change in this measure in the placebo group [4.0 (2.2) and 3.3 (2.3) respectively]. This was not at the expense of a significant increase in dyskinesia. However, there was no difference between the groups when comparing their average Hoehn and Yahr stage of disease, and Schwab and England activities of daily living index.
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.