Continuous subcutaneous apomorphine therapy improves dyskinesias in Parkinson's disease: a prospective study using single-dose challenges.

Continuous subcutaneous (SC) infusion of the dopamine agonist apomorphine was shown in retrospective studies to improve drug-induced dyskinesias in Parkinson's disease (PD). We prospectively assessed the antidyskinetic effect of continuous SC apomorphine therapy using subjective and objective measures, and sought to determine whether any observed dyskinesia reduction could be corroborated using single-dose dopaminergic challenges. Twelve PD patients with on-off fluctuations and disabling dyskinesias who were scheduled to start apomorphine pump treatment underwent acute levodopa and apomorphine challenges at baseline and 6 months later. Video recordings involving motor tasks were rated blindly by two independent raters using modified AIMS and Goetz dyskinesia scales. At 6 months, mean apomorphine dose was 75.2 mg per day and the mean L-dopa dose had been reduced by 55%. Daily off time in patients' diaries was reduced by 38% (2.4 hours). The L-dopa challenges showed a reduction of 44% in AIMS and 40% in Goetz scores (both P < 0.01). Apomorphine challenges showed a reduction of 39% in AIMS and 36% in Goetz scores (both P < 0.01). Patients' self-assessment scores reflected these significant changes. Dyskinesia improvement correlated with reduction in oral medication and with the final apomorphine dose (P < 0.05). This prospective study confirms marked dyskinesia reduction on continuous subcutaneous apomorphine therapy, paralleled by reduced dyskinesias during dopaminergic challenge tests. Our findings support the concept that replacement of short-acting oral antiparkinsonian medication with continuous dopamine receptor stimulation may reverse, at least partially, the sensitization process believed to mediate the development of drug-induced dyskinesias in PD.     

Motor features and response to oral levodopa in patients with Parkinson’s disease under continuous dopaminergic infusion or deep brain stimulation

Background: Subthalamic nucleus deep brain stimulation (STN DBS) and continuous dopaminergic infusions (jejunal levodopa or subcutaneous apomorphine) are indicated in complicated Parkinson’s disease (PD), although it remains unsettled how they compare to each other. Methods: We investigated the daytime motor condition in patients with advanced PD under monotherapy with jejunal levodopa, subcutaneous apomorphine, or STN DBS and also measured the motor changes produced by an additional standard morning dose of levodopa. Motor performance was assessed with the UPDRS‐III, hand taps, the AIMS dyskinesia score and patients’ diaries. Outcome measures were time to best motor ‘on’ after start of morning treatment, daytime variability of motor condition, motor scores. Results: The time to ‘on’ was longest in the jejunal levodopa group. DBS and jejunal levodopa treatments produced stable motor conditions without appreciable ‘off’ episodes. Continuous apomorphine infusion was associated with the worst motor scores (UPDRS‐III and taps) and the most frequent off‐states. Jejunal levodopa infusion was associated with the highest AIMS scores. Addition of a levodopa dose produced shortening of time to ‘on’ and a transient motor improvement in the jejunal levodopa group without increase in dyskinesias; in the DBS and apomorphine groups, there was an increase in dyskinesias without changes in UPDRS‐III or taps. Conclusions: STN DBS provided adequate trade‐off between motor improvement and dyskinesia control, although dyskinesias could be elicited by adding oral levodopa. Jejunal levodopa infusion produced adequate motor improvement with slow time to ‘on’ and moderate dyskinesias. Apomorphine infusion produced insufficient motor control and negligible dyskinesias.     

Similar effect of estradiol and haloperidol on experimental tardive dyskinesia in monkeys

In a group of ovariectomized monkeys, a persistent buccolingual dyskinesia resembling tardive dyskinesia was induced by an upper midbrain lesion. This dyskinesia was increased by apomorphine. A single dose of haloperidol (1 mg/kg) reduced the effect of apomorphine after 24 hours and caused an increase in CSF homovanillic acid. Fifteen days later, however, the response to apomorphine was markedly enhanced. Estradiol benzoate (0.5 mg sc) had a similar biphasic effect, although of lesser magnitude. In a different group of lesioned but non-dyskinetic animals, the CSF concentration of HVA also was elevated 24 hours after estradiol. These results support our hypothesis that estradiol shares several properties with neuroleptics, and in particular, reduces, then enhances the sensitivity of striatal dopaminergic receptors.     

Apomorphintherapie versus tiefe Hirnstimulation Klinische und ökonomische Aspekte bei Patienten mit fortgeschrittenem Morbus Parkinson

Long-term dopaminergic treatment of Parkinson's disease is complicated by the occurrence of dyskinesia and motor fluctuations and is responsible for increasing the costs of treatment. In these patients, continuous subcutaneous therapy with the dopamine agonist apomorphine or deep-brain stimulation represents a promising strategy. While the costs for the treatment with apomorphine are covered by health insurance, separate reimbursement for deep-brain stimulation does not exist in Germany. The case reports (n = 3) presented here emphasize that deep-brain stimulation is less cost-intensive than subcutaneous treatment with apomorphine in selected patients. Even in the first postoperative year costs for medication and hospital stays were reduced by approximately 60%. Moreover, in all three patients, motor complications improved after deep-brain stimulation in comparison to previous subcutaneous application of apomorphine. Thus, to further ensure deep-brain stimulation in parkinsonian patients it is mandatory to find a mode of reimbursement for the institutions concerned.     

Drug-induced dyskinesia in primates rendered hemiparkinsonian by intracarotid administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

The right common carotid artery was surgically exposed under general anaesthesia in 6 cynomolgus monkeys and MPTP (0.5–2.2 mg/kg) directly infused. This produced a hemiparkinsonian syndrome in the contralateral limbs which responded to treatment with both levodopa and apomorphine. these drugs also precipitated dose-dependent contralateral rotation which reached a peak 2 weeks after MPTP infusion. A massive depletion of large, presumably dopaminergic cells was found from the ipsilateral substantia nigra pars compacta. Three animals receiving chronic therapy with apomorphine developed choreoathetoid movements of the limbs and the face contralateral to the infusion 2 weeks after the commencement of treatment. The severity of the dyskinesia gradually increased and after 4 weeks peak-dose hemiballistic movements were seen. Levodopa and the selective D-2 and D-1 dopamine agonists LY-171555 and SKF 38393 also reversed parkinsonian features and produced contralateral rotation and peak-dose dyskinesia. This unilateral model of parkinsonism in the primate will be of value in the elucidation of the mechanisms by which chronic levodopa or dopamine agonist therapy enhance involuntary movements in parkinsonism.     

A randomized, double-blind, placebo-controlled trial of subcutaneously injected apomorphine for parkinsonian off-state events

OBJECTIVE: To assess the safety and efficacy of subcutaneous apomorphine hydrochloride administration for off-state (poor motor function) periods in patients with Parkinson disease with motor fluctuations under both inpatient titration and outpatient therapeutic conditions. PATIENTS AND METHODS: Twenty-nine patients had advanced Parkinson disease with 2 hours or more off time despite aggressive oral therapy. Patients randomly received titrated doses of subcutaneous apomorphine hydrochloride (2-10 mg, n = 20) or pH-matched vehicle placebo (n = 9) during an inpatient and 1-month outpatient phase. A change in the United Parkinson Disease Rating Scale motor score 20 minutes after inpatient dosing during a practically defined off-state event and the percentage of injections successfully aborting off-state events were the primary inpatient and outpatient efficacy factors. RESULTS: The average (SEM) levodopa equivalent dose of apomorphine hydrochloride was 5.4 +/- 0.5 mg and the mean placebo dose was 1.0 mL. Mean inpatient United Parkinson Disease Rating Scale motor scores were reduced by 23.9 and 0.1 points (62% and 1%) by apomorphine treatment and placebo, respectively (P<.001). The mean percentage of outpatient injections resulting in successful abortion of off-state events was 95% for apomorphine and 23% for placebo (P<.001). Inpatient response was significantly correlated with and predictive of outpatient efficacy (P<.001). The levodopa dose was not predictive of the apomorphine dose requirement. Frequent adverse events included dyskinesia, yawning, and injection site reactions. CONCLUSION: Apomorphine by intermittent subcutaneous injection is effective and safe for outpatient use to reverse off-state events that occur despite optimized oral therapy.     

Open-label pilot study of levetiracetam (Keppra) for the treatment of levodopa-induced dyskinesias in Parkinson's disease.

We evaluated the tolerability and preliminary efficacy of levetiracetam (LEV; Keppra) in reducing levodopa-induced dyskinesias in Parkinson's disease (PD) in an open-label pilot study. Nine PD patients who were experiencing peak-dose dyskinesias for at least 25% of the awake day and were at least moderately disabling were treated with LEV in doses up to 3,000 mg for up to 60 days. The primary outcome measure was the percent of the awake day that patients spent on without dyskinesia or with nontroublesome dyskinesia (good on time). The mean dose of LEV at endpoint was 625+/-277 mg/day. LEV significantly improved percent of the awake day on without dyskinesia or with nontroublesome dyskinesia at endpoint compared to baseline (43% +/- 12% vs. 61% +/- 17%; P=0.02). Percent on time with troublesome dyskinesia decreased from 23% +/- 10% at baseline to 11% +/- 6% at endpoint, although not significantly. There was no significant increase in off time from baseline to endpoint. There was a 56% dropout rate, mostly due to somnolence. In PD patients who experienced peak-dose dyskinesia for at least 25% of the awake day, LEV significantly improved on time without dyskinesia or with nontroublesome dyskinesia.     

Midification of tardive dyskinesia and spasmodic torticollis by apomorphine. Possible role of dopamine autoreceptors

A group of 16 patients afflicted with involuntary movement disorders received subcutaneous injections of the direct dopamine agonist, apomorphine hydrochloride. Paradoxically, these injections were generally followed by a reduction of dyskinesia; this was most noticeable in patients with tardive dyskinesia and was only mild in some patients with spasmodic torticollis. Preferential stimulation by apomorphine of inhibitory dopamine presynaptic receptors (so-called dopamine autoreceptors) is proposed as the most likely explanation for the observed antidyskinetic effect of this drug. The results of this study also suggest that direct dopamine agonists may be used clinically to attenuate CNS dopaminergic transmission, especially when use of antidopminergic drugs such as the nuroleptics is contraindicated, as in the case of tardive dyskinesia.     

Neural mechanisms underlying peak-dose dyskinesia induced by levodopa and apomorphine are distinct: evidence from the effects of the alpha(2) adrenoceptor antagonist idazoxan.

Dyskinesia, secondary to dopamine replacement therapy, is the major complication of currently available therapies for Parkinson's disease. Alpha(2) adrenoceptor antagonists, such as idazoxan, can significantly reduce levodopa-induced dyskinesia in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned, nonhuman primate model of Parkinson's disease and in human. This action of adrenoceptor antagonists may involve blockade of the actions of noradrenaline synthesised from levodopa. We hypothesise that, because dopamine receptor agonists, such as apomorphine, cannot be metabolised to produce noradrenaline, activation of adrenoceptors may not be involved in dyskinesia produced by such agents. If this were the case, idazoxan would not be expected to reduce apomorphine-induced dyskinesia. MPTP-lesioned marmosets with stable dyskinesia induced by prolonged levodopa therapy were given an acute challenge with apomorphine (0.3 mg/kg subcutaneously) or levodopa (8.0 mg/kg orally), these doses produced equivalent peak-dose dyskinesia. Idazoxan (2.5 mg/kg p.o.), or vehicle, was then administered with either apomorphine or levodopa. Idazoxan abolished levodopa-induced dyskinesia but did not affect apomorphine-induced dyskinesia (P < 0.05 and P > 0.05, respectively, Wilcoxon matched pairs test). Idazoxan also extended the anti-parkinsonian actions of levodopa but did not affect those of apomorphine. The pharmacological characteristics of the neural mechanisms underlying levodopa-induced dyskinesia and apomorphine-induced dyskinesia in parkinsonism thus appear to be distinct, at least with respect to the involvement of alpha(2) adrenoceptors. Specifically, levodopa, but not apomorphine-induced dyskinesia, involves activation of adrenoceptors. This finding may have major implications for understanding dyskinesia and should be borne in mind when designing clinical studies in which levodopa or dopamine receptor agonist challenges are employed to assess potential anti-dyskinetic properties of drugs.     

Severity of Parkinson''s disease is a risk factor for peak-dose dyskinesia.

Fifty four patients with idiopathic Parkinson's disease receiving levodopa therapy were studied. Thirty three of these patients displayed peak-dose dyskinesia. Neither the duration of Parkinson's disease nor the duration of levodopa therapy discriminated between patients with and patients without peak-dose dyskinesia. Consequently, these criteria could not determine whether the first appearance of peak-dose dyskinesia depends on the duration of Parkinson's disease--a factor that is related to the severity of the disease--or on the duration of levodopa therapy. A subgroup of nineteen patients with unilateral or unequivocally asymmetrical peak-dose dyskinesia was examined 12 hours after withdrawal of levodopa. A levodopa testdose provoked unilateral or unilateral preponderant peak-dose dyskinesia which always involved the most severely affected side and which also happened to be the side of onset of the disease. This demonstrates that the severity of Parkinson's disease is the main risk factor for peak-dose dyskinesia.     

Apomorphine: an underutilized therapy for Parkinson's disease.

Apomorphine was the first dopaminergic drug ever used to treat symptoms of Parkinson's disease. While powerful antiparkinsonian effects had been observed as early as 1951, the potential of treating fluctuating Parkinson's disease by subcutaneous administration of apomorphine has only recently become the subject of systematic study. A number of small scale clinical trials have unequivocally shown that intermittent subcutaneous apomorphine injections produce antiparkinsonian benefit close if not identical to that seen with levodopa and that apomorphine rescue injections can reliably revert off-periods even in patients with complex on-off motor swings. Continuous subcutaneous apomorphine infusions can reduce daily off-time by more than 50% in this group of patients, which appears to be a stronger effect than that generally seen with add-on therapy with oral dopamine agonists or COMT inhibitors. Extended follow-up studies of up to 8 years have demonstrated long-term persistence of apomorphine efficacy. In addition, there is convincing clinical evidence that monotherapy with continuous subcutaneous apomorphine infusions is associated with marked reductions of preexisting levodopa-induced dyskinesias. The main side effects of subcutaneous apomorphine treatment are related to cutaneous tolerability problems, whereas sedation and psychiatric complications play a lesser role. Given the marked degree of efficacy of subcutaneous apomorphine treatment in fluctuating Parkinson's disease, this approach seems to deserve more widespread clinical use.     

A 10 year retrospective audit of long-term apomorphine use in Parkinson’s disease

Abstract Objectives Apomorphine is a potent dopamine agonist useful in the treatment of Parkinsons disease patients with disabling motor fluctuations and off periods, not responding to oral medication. It can also be of benefit in reducing dyskinesia by providing more constant dopaminergic stimulation and permitting lower levodopa dosage. However, there is a paucity of information on long-term benefits of apomorphine, including no large-scale phase III trial. We have examined our experience of apomorphine over the last 10 years, to assess indications, pattern of use, efficacy, and side effect profile. Methods All patients requiring apomorphine were identified through the Parkinsons disease Nurse Specialists records. An audit form was produced so that the same information was gathered from all case-notes. Results There were 107 patients (61 males and 46 females). Mean age of disease onset was 50.9 years, SD±9.3 (range 29–78). The mean duration of disease at start of apomorphine treatment was 10 years (SD±4.8, range2–29). The most common indications for apomorphine were severe unpredictable off periods (75.7 %), motor fluctuations (18.7 %) and dyskinesia (5.6 %). Most patients (63.6 %) used both intermittent subcutaneous injections and infusion via pump; 25.2% were on intermittent injection, and 11.2 % infusion alone. Mean dose per injection was 3.7mg. Mean infusion dose 69.8mg, running over a mean of 13.5 hours. The mean duration of intermittent apomorphine use was 48.2 months. The mean duration of infusion was 25.1 months. Complications included skin problems in 16 patients, 2 had symptomatic hypotension, 2 worsening confusion, 1 new confusion and 5 new hallucinations (after sometime on apomorphine). Sixteen patients have stopped using apomorphine completely. Thirteen have stopped the pump, but continue on intermittent injections. Conclusion Subcutaneous apomorphine is easy for patients to use, is well tolerated and has a low incidence of side effects, especially confusion.     

Subcutaneous administration of apomorphine in motor fluctuations in Parkinson's disease

Apomorphine, a dopaminergic agonist was given over a period of 12 months to 14 parkinsonian patients suffering from severe L-dopa induced on-off effects. Nine patients (mean age: 52 years; mean age at onset of the disease: 37 years), were treated by continuous infusion with a portable minipump, and 5 others by multiple injections with a penject. The mean duration of daily off periods was reduced by two thirds in all patients. The motor fluctuation intensity was only diminished in the 9 patients treated by continuous infusion. These patients received a mean apomorphine daily dose of 93 mg and L-dopa dosage was reduced by 53 p. 100. Red fibrous subcutaneous nodules occurred at the injection sites in all patients treated by infusion. This study confirms the effectiveness of subcutaneous apomorphine administration in the treatment of severe motor fluctuations.     

Effects of central dopaminergic stimulation by apomorphine on speech in Parkinson's disease

OBJECTIVE: To determine the effect of central dopaminergic stimulation with apomorphine on speech in PD. BACKGROUND: Most patients with PD have a speech disorder. Of those, 89% have involvement of laryngeal function, and 45% have additional articulatory dysfunction. The effect of dopaminergic medications on these two dimensions of speech impairment in PD has not been selectively studied. METHODS: In a randomized, double-blind, placebo-controlled crossover design, patients with PD and speech impairment, Hoehn and Yahr stages 2 to 4 "off," and without severe dyskinesias were given placebo or apomorphine injections 0.05 mg/kg subcutaneously during two consecutive outpatient visits. They were pretreated with domperidone for 48 hours and were tested off their parkinsonian medications for 12 hours. Laryngeal function was assessed by maximum sustained vowel phonations and comfortable vowel phonations. Articulatory function was evaluated by speech intelligibility score, speaking rate, and efficiency ratio. RESULTS: Ten patients, mean age 73.4 years (SD = 6.6), disease duration 8.7 years (SD = 6.3), were tested. The baseline motor score on the Unified Parkinson's Disease Rating Scale (UPDRSm) and all experimental speech variables were equivalent on both placebo and apomorphine days. At a dose of apomorphine that provoked improvement in UPDRSm (p = 0.0078), no index of either laryngeal or articulatory function improved significantly after apomorphine administration. CONCLUSION: Laryngeal and articulatory speech components are not under prominent dopaminergic control in PD. Treatment regimens should focus on nondopaminergic pharmacology and other therapies.     

Effect of riluzole on dyskinesia and duration of the on state in Parkinson disease patients: a double-blind, placebo-controlled pilot study

The objective of this study was to evaluate the effect of riluzole on dyskinesia and the duration of the ON state in patients with Parkinson disease (PD). The authors studied 16 PD patients with levodopa-induced dyskinesia. All patients initially received an apomorphine dose intended to induce the motor function benefit (ON state) generally accompanied by dyskinesia. They evaluated the patients during the OFF and ON states using the UPDRS-III, UPDRS-IV, and Larsen scales, and measured the duration of the ON state. Patients were randomly assigned to receive either riluzole (50 mg bid) or placebo for 7 consecutive days (8 patients in each group). The authors did not interrupt previously prescribed medication. Following the 7-day period, they carried out similar evaluation procedures before and after another apomorphine challenge. Mean UPDRS-IV scores were 6.1 points and 6.0 points before and after riluzole therapy respectively. For the placebo group, the scores were 6.9 points and 6.6 points for the initial and final evaluations respectively. Larsen scale had mean scores of 9.2 points and 9.9 points for the pre- and postriluzole periods, and 10.2 points and 9.6 points for pre- and post-placebo evaluations respectively. The ON state was 33.5% lengthier after 7 days of riluzole and 28.0% lengthier after placebo. They could not find any statistical differences between the 2 groups. Short-term riluzole administration in PD patients was not able to reduce apomorphine-induced dyskinesia but could extend the ON state duration, although this did not reach statistical significance.     

Effect of bilateral subthalamic deep brain stimulation on diphasic dyskinesia

OBJECTIVES: The goal of this study was to assess the effect of bilateral subthalamic deep brain stimulation (STN DBS) on levodopa-induced diphasic dyskinesia in patients with Parkinson disease (PD). PATIENTS AND METHODS: Six PD patients with diphasic dyskinesia were included in this study. Prior to surgery, the duration and severity of dyskinesia were determined in each patient, along with the Unified Parkinson Disease Rating Scale score and Hoehn and Yahr stage. Bilateral STN electrode implantation was performed during a single operation. RESULTS: The median duration of the follow-up period was 21.5 months (range 14-24 months). STN DBS had a beneficial effect on diphasic dyskinesia in all patients. At the last follow-up, 3 patients had no dyskinesia and 1 had only a small amount of peak-dose dyskinesia. One patient showed a reduction in the duration of diphasic dyskinesia, despite a lack of reduction in the total duration of dyskinesia. In the last patient, although the total duration of dyskinesia increased, the pattern of dyskinesia changed from severe painful disabling dyskinesia to the less severe peak-dose type of dyskinesia. There were no intraoperative or postoperative surgical complications. CONCLUSIONS: Bilateral STN DBS is good at reducing diphasic dyskinesia, and it can be a good therapeutic option for patients with diphasic dyskinesia.     

Apomorfina w zaawansowanej chorobie Parkinsona

Apomorphine is the most potent dopamine receptor agonist and its symptomatic effectiveness is comparable to levodopa. Subcutaneous apomorphine is rapidly and completely absorbed. Plasma peak concentrations are achieved after 5–15 minutes and onset of clinical effect is within 20 minutes. Apomorphine intermittent subcutaneous injections are effective as rescue therapy for unpredictable off periods in advanced Parkinson disease (PD). More often apomorphine is administered as a subcutaneous infusion which secures the continuous dopaminergic stimulation. The benefit on ‘off’ periods is consistent across all studies, but dyskinesia improvement is not so obvious. Two infusion therapies (apomorphine and intraduodenal levodopa) and deep brain stimulation (DBS) are effective in advanced PD patients with untreatable motor complications. Apomorphine infusions should be considered in patients unable to undergo DBS because of cognitive impairment and neurosurgical contraindications.     

Clinical pattern and risk factors for dyskinesias following fetal nigral transplantation in Parkinson's disease: A double blind video‐based analysis

The objective of this study is to assess dyskinesias in 34 Parkinson's disease patients randomized to receive bilateral fetal nigral transplantation with 4 donors per side (12), 1 donor per side (11), or placebo (11). Videotape recordings were performed at the baseline, 3, 6, 12, 18, and 24 month visits during the “practically defined off” (12 hours after last evening dopaminergic therapy) and “best on” (best response following morning dopaminergic therapy) states. Videotapes were analyzed in random order by a blinded investigator. Dyskinesias during “best on” (on‐medication dyskinesia) were observed in all, but 1 patient at baseline, and in all patients at each subsequent visit. There were no differences between groups. No patient had dyskinesia at baseline in “practically‐defined off” (“off‐medication” dyskinesia). Following transplantation, off‐medication dyskinesia was observed in 13 of 23 patients, but not in any patient in the placebo group (P = 0.019). There was no difference in dyskinesia score between patients in the 1 and 4 donor groups. On‐medication dyskinesias were typically generalized and choreiform, whereas off‐medication dyskinesias were usually repetitive, stereotypic movements in the lower extremities with residual Parkinsonism in other body regions. Off‐medication dyskinesias are common following transplantation and may represent a prolonged form of diphasic dyskinesias. © 2008 Movement Disorder Society     

Diurnal fluctuations in plasma carbamazepine level in children with epilepsy

After determination of carbamazepine level in plasma by means of gas chromatography 23 profiles of 24-hour concentrations were plotted in children aged from 20 months to 15 years treated for epilepsy. In 12 of them monotherapy was given (Amizepin-Polfa in a mean daily dose of 18.7 mg/kg) while polytherapy was given to 11 children (mean daily dose was 21.1 mg/kg). Considerable fluctuations of the level of the drug were found in the plasma over 24 hours in various children, and individual differences after the administration of carbamazepine alone or with other drugs. The 24-hour fluctuations of total carbamazepine in the plasma and individual differences are due, probably, to pharmacokinetic factors due to physiological differences between patients and were correlated more to the age of the child than to the administered dose.     

Levodopa treatment does not affect low-dose apomorphine test in patients with Parkinson's disease.

Challenge with low-dose apomorphine causes a significant rise in growth hormone (GH) in patients with Parkinson's disease (PD) compared to controls and patients with multiple system atrophy (MSA) who have not previously received dopaminergic treatment. To date, it has not been demonstrated whether an apomorphine-induced rise in GH can still be detected in PD patients who are currently treated with levodopa. We investigated whether an ongoing treatment with levodopa influences the GH response to subcutaneously applied low-dose apomorphine in PD patients. We studied 44 patients with idiopathic PD using the low-dose apomorphine test. Twenty-three patients were under treatment with levodopa and 21 patients were without any dopaminergic therapy. GH and cortisol levels were analyzed at time of injection and 45 minutes and 60 minutes after subcutaneous apomorphine injection. Forty-five minutes after apomorphine injection, there was no significant difference between the mean rise in plasma GH in untreated PD patients compared with levodopa-treated patients (P = 0.235). There was no increase of cortisol levels in each treatment group. Age, sex, duration, and severity of the disease did not show a covariate effect with GH levels. A small group of PD patients (n = 8) treated with dopamine agonists and a small group of patients with MSA (n = 5) as well as patients with vascular parkinsonism (n = 5) did not show any increase of GH. Our data suggest that the apomorphine-induced rise in GH does not depend on previous levodopa treatment in PD patients but, as expected, is blocked by dopamine agonists and is not present in patients with other than idiopathic parkinsonian syndrome. Thus, the low-dose apomorphine test may also be a useful biological marker in the early differential diagnosis of PD patients who have already received levodopa treatment.