Therapeutic efficacy of apomorphine combined with an extracerebral inhibitor of dopamine receptors in Parkinson's disease

Use of apomorphine in Parkinson's disease

Apomorphine is a dopamine agonist administered subcutaneously as intermittent injections or in a continuous infusion. It is useful in managing advanced Parkinson's disease, and provides an alternative to neurosurgical procedures. This review summarizes indications and practical guidelines for its use.

A new video/computer method to measure the amount of overall movement in experimental animals (two-dimensional object-difference method)

Evaluation of the amount of overall animal movement is important for investigations of motor control mechanisms in the central nervous system. We describe a new method to quantify overall free movements of an animal without any markers using a video camera and a personal computer equipped with a video-capture board. The operating principle is that the amount of overall movement of an object can be expressed by the difference in total area occupied by the object in two consecutive picture frames. The software for this application operates in real-time. Using this method and with proper setting for the cage and recording view, we can estimate three-dimensional movements of animals. The major advantages are low cost, easy operation and high sensitivity. The experimental results indicate that this method can be applied to various fields of motion analysis.

Motor fluctuations in Parkinson's disease: pathophysiology and treatment

At the initial stages of Parkinson's disease (PD), levodopa (LD) is able to reduce most motor symptoms and to significantly improve the patient's quality of life. However, in the vast majority of patients with prolonged LD usage, some decline in efficacy occurs and motor complications eventually begin to appear. These complications consist not only of daily fluctuations in the voluntary motor performance often accompanied by involuntary movements, but also of fluctuations in cognitive, autonomic, and sensory functions. Several recent studies on LD complications in PD have led to a better understanding of their pathophysiology and of the possible therapeutic interventions, and a summary of these findings is presented in this review. Different observations now suggest that postsynaptic pharmacodynamic factors play a major role in determining fluctuations in PD. Two explanations are given: chronic intermittent dopaminergic therapy may lead to postsynaptic receptor downregulation in PD; or, receptor changes in the striatum may occur independently of treatment as a result of structural adaptation of the postsynaptic dopaminergic system to the progressive decline of the nigrostriatal pathway. The hypothesis of reversible postsynaptic changes as the main mechanism underlying a fluctuating response to LD lends itself to a possible pharmacological manipulation of the dopaminergic response to reverse, or even avoid, motor fluctuations (initial monotherapy with dopamine agonists and early combination LD/dopamine agonists). The role of peripheral pharmacokinetics factors is also critical and the use of controlled release LD formulations, of monoamine oxidase (MAO)-B and of catechol-O-methyltransferase (COMT) inhibitors may all, to a different degree, improve such phenomena. In the last decade, there has been a resurgence in surgical therapies in advanced PD, due to higher levels of accuracy and safety provided by the new surgical devices, and to a more precise localization of the target areas allowed by the neurophysiological mapping techniques. The surgical procedures currently used in advanced PD are stereotactic brain lesions (internal globus pallidus and subthalamic nucleus), chronic brain stimulation (of the same nuclei) and striatal grafting of dopamine-producing cells. All these procedures have already shown their efficacy in the management of severe fluctuations in PD, but their indications, and relative advantages and disadvantages, are still the subject of considerable debate and controversy.

Subcutaneous apomorphine in late stage Parkinson's disease: a long term follow up

OBJECTIVES

Despite the recent introduction of new peroral drugs as well as neurosurgical methods for Parkinson's disease, treatment of late stage parkinsonian patients remains difficult and many patients become severely handicapped because of fluctuations in their motor status. Injections and infusions of apomorphine has been suggested as an alternative in the treatment of these patients, but the number of studies describing the effects of such a treatment over longer time periods is still limited. The objective was to investigate the therapeutic response and range of side effects during long term treatment with apomorphine in advanced Parkinson's disease.

METHODS

Forty nine patients (30 men, 19 women; age range 42-80 years) with Parkinson's disease were treated for 3 to 66 months with intermittent subcutaneous injections or continuous infusions of apomorphine.

RESULTS

Most of the patients experienced a long term symptomatic improvement. The time spent in "off" was significantly reduced from 50 to 29.5% with injections and from 50 to 25% with infusions of apomorphine. The quality of the remaining "off" periods was improved with infusion treatment, but was relatively unaffected by apomorphine injections. The overall frequency and intensity of dyskinesias did not change. The therapeutic effects of apomorphine were stable over time. The most common side effect was local inflammation at the subcutaneous infusion site, whereas the most severe were psychiatric side effects occurring in 44% of the infusion and 12% of the injection treated patients.

CONCLUSION

Subcutaneous apomorphine is a highly effective treatment which can substantially improve the symptomatology in patients with advanced stage Parkinson's disease over a prolonged period of time.

A double-blind, placebo-controlled study of intranasal apomorphine spray as a rescue agent for off-states in Parkinson's disease

Nine patients with advanced levodopa-responsive Parkinson's disease were enrolled in a double-blind, placebo-controlled crossover trial of intranasal apomorphine as rescue therapy for parkinsonian off-states. Patients were assigned in random order to each of four possible combinations of apomorphine, trimethobenzamide antiemetic, and their matched placebos and received detailed in-office motor scoring during each of the four study periods. Patients also completed diaries describing the effectiveness of the nasal spray for reversing off-states. A statistically significant reduction in the Unified Parkinson's Disease Rating Scale (UPDRS) motor score was seen following active apomorphine during in-office evaluation visits but not following placebo nasal spray. Patient diaries revealed that active apomorphine had a latency to onset of 11 minutes and a duration of 50 minutes. Significant nausea from apomorphine spray was seen in only one patient whereas nasal irritation was disabling in three and mild in two. We conclude that intranasal apomorphine is an effective rescue agent for parkinsonian off-states although nasal irritation is a limiting factor.

Determination of apomorphine in human plasma by alumina extraction and high-performance liquid chromatography with electrochemical detection

Apomorphine is a powerful agonist of dopaminergic receptors which several years ago was introduced into the therapy of Parkinson's Disease. The pharmacological activity of apomorphine already appears significant at low doses. Unfortunately, the difficulty in determining the drug in plasma at low concentrations hampers the completion of accurate pharmacokinetic studies in humans. Considering the analogy of apomorphine with the molecular structure of catecholamines, the extraction of the drug from plasma was optimized by using adsorption on alumina, a technique widely used for noradrenaline and adrenaline analysis in clinical chemistry laboratories. This method proved particularly efficient and selective in apomorphine extraction from plasma prior to high-performance liquid chromatographic analysis. After pretreatment of 200 microliters of plasma sample with 40 mg of alumina and 10 microliters of tris buffer (pH 8.6), the drug was eluted with 200 microliters of an acidic-organic solution. One volume of the supernatant was mixed with two volumes of phosphate buffer (pH 3.6), and 100 microliters of the obtained mixture were injected into the HPLC system. The chromatograph was equipped with a C18 reversed-phase column and with an electrochemical coulometric detector fitted with a high-sensitivity cell (first electrode 0.00 volts, second electrode +0.35 volts). Sensitivity (20 pg of injected drug), precision (CV within assay and between assays of 3.7% and 5.6%, respectively) and accuracy were comparable to more complex analytical procedures. The miniaturisation of the entire sample pretreatment proved very advantageous for pharmacokinetics studies and, in principle, for therapeutic drug monitoring and toxicological investigations.

[Apomorphine: an alternative in the control of motor fluctuations in Parkinson's disease]

Levodopa-induced motor fluctuations (MF) is a disabling complication of Parkinson's disease (PD) and is usually refractory to conventional treatment. Apomorphine, a dopamine agonist with affinity for both D1 and D2 receptors, has been emerged as an useful alternative in the management of MF of PD. The frequency of nausea and vomiting prevented its use in the past, but the simultaneous administration of domperidone has proved to be able to control these side effects. Although apomorphine has been successfully used to control levodopa-induced MF in other countries, it has not been considered in the management of PD in Brazil. We report here our initial experience with subcutaneous injections of apomorphine combined to oral domperidone. We administered apomorphine in doses ranging from 1.5 to 3 mg in four PD patients with MF of our outpatient clinic. All the doses administered switched the "off" state to a motor response qualitatively similar to what is seen in the "on" phase induced by levodopa, including the occurrence of dyskinesia. The latency to turn "on" after apomorphine ranged from 7 to 30 minutes and the duration of the response ranged from 60 to 85 minutes. We observed yawning in all four patients, labial paresthesia in one patient and an inspecific unpleasant sensation in another patient. These side effects were not significant in our four patients. Our data show that the use of apomorphine adds a reliable and effective strategy in the management of MF of PD patients.

Median nerve somatosensory evoked potentials. Apomorphine-induced transient potentiation of frontal components in Parkinson's disease and in parkinsonism

Somatosensory evoked potentials (SEPs) to median nerve stimulation have been recorded from parietal and frontal districts in 43 parkinsonians, 17 patients with parkinsonism and 35 healthy controls matched for age and sex. Latency/amplitude characteristics of the parietal P14-N20-P25 and of the frontal P20-N30-P40 wave complexes before and after (10, 20, 30 and 60 min) subcutaneous administration of apomorphine chloride were evaluated in all the 60 patients and in 3 controls. The frontal waves N30 and P40 were either absent or significantly smaller than normal in 31 patients with Parkinson's disease (PD) (72.1%) and in 9 with parkinsonism in baseline records (56.3%). Following apomorphine, the parietal deflections did not significantly vary in amplitude. On the contrary, the frontal complex showed a significant amplitude increase in 27 PD and 8 parkinsonisms (respectively 62.8 and 47.1%); 79.1% of PD and 35.3% of parkinsonisms were improved clinically. Amplitude increase was evident at 10 min after apomorphine, in parallel with clinical improvement, and vanished nearly in coincidence with the end of the clinical effect.

Apomorphine for motor fluctuations and freezing in Parkinson's disease

OBJECTIVE

To review the pharmacokinetics and use of apomorphine in patients with Parkinson's disease; to report a case of beneficial outcome with apomorphine in a patient with Parkinson's disease with severe levodopa "on-off" fluctuations and freezing; and to outline the types of patients or situations where apomorphine may be useful.

DATA SOURCES

Case reports, review articles, and relevant clinical studies identified by a MEDLINE search of the English-language literature published between 1975 and October 1994.

STUDY SELECTION

Because all but 2 reports were of open-label design with small sample sizes, all studies identified were evaluated.

DATA EXTRACTION

The following data were extracted from each study: apomorphine treatment duration, dosing, onset, duration, and adverse effects. The following efficacy variables were extracted: percent decrease in off periods, improvement in parkinsonian symptoms, and percent decrease in levodopa dosage.

DATA SYNTHESIS

Efficacy of apomorphine following subcutaneous, rectal, sublingual, and intranasal dosage forms are evaluated. We also describe the use of apomorphine in a patient with Parkinson's disease who experienced on-off fluctuations and freezing. Based on these reports, recommendations for patient selection, product selection, and apomorphine dosing guidelines are presented.

CONCLUSIONS

Apomorphine decreases off time, freezing, and levodopa requirements in patients with Parkinson's disease. It can be administered via a number of different nonoral routes; however, subcutaneous apomorphine is the most extensively studied. Rectal, sublingual, and intranasal routes also have been shown to provide benefit in motor fluctuations, but differ from the subcutaneous route in onset of action, duration of effect, and adverse effect profile.

Apomorphine in patients with Parkinson's disease

We present a review of the recent literature and personal experience with apomorphine in patients with Parkinson's disease. Apomorphine is a potent D1 and D2 dopaminergic agonist. It has a rapid and short duration effect after subcutaneous administration at doses ranging from 15 to 180 micrograms/kg. Plasma maximal concentration is reached in 8-16 minutes, with a plasma half life of 34-70 minutes. Bioavailability is close to 100%. Repeated injections in patients show post-stimulative hyposensitivity. Apomorphine test appears very useful for the differential diagnosis between idiopathic Parkinson's disease and other Parkinson plus syndromes, and as a predictive test for dopaminergic responsiveness. Appropriate doses are able to alleviate akinesia, rigidity and tremor. Recent therapeutic trials have demonstrated the high interest of intermittent multiple subcutaneous apomorphine injections to cut the "off" motor phases in fluctuating parkinsonian patients under chronic levodopa treatment. In some cases, continuous apomorphine subcutaneous infusion with a portable pump may be required, particularly when levodopa treatment is temporarily interrupted, as after abdominal surgery. During long-term treatment, the apomorphine dose able to relieve akinesia remains stable. Peripheral side effects such as nausea and hypotension may be prevented by the co-administration of domperidone, a peripheral dopaminergic antagonist. Cutaneous fibrous nodules and psychiatric symptoms may occur, but usually at high dosages with continuous infusion. Local allergic effects have limited the use of other routes of administration, such as intranasal, sublingual, and rectal routes. Apomorphine is also used as a pharmacological tool for clinical research with the aim of a better understanding of the pathophysiology of Parkinson's disease.

Comparison of two software programs to be used for the calculation of population pharmacokinetic parameters

The pharmacokinetic parameters of apomorphine, a potent dopamine agonist, were calculated after subcutaneous and intranasal administration. Two available software packages for TDM were used (USC*PACK and MW/PHARM). The findings for the calculated parameters Kel, Vslope, Ka and bioavailability were compared. Although small, sometimes significant differences were found, the NPEM program from the USC*PACK collection provides most information about the population under investigation. We found a median Vslope of 1.7408 +/- 0.8461 (S.D.) 1/kg, and a mean Kel of 1.5341 +/- 0.3748 h-1. The absorption after intranasal administration was extremely rapid: Ka = 20.5 +/- 1.96 h-1, comparable with that found with subcutaneous absorption: Ka = 23.04 +/- 2.20 h-1.

Apomorphine test for dopaminergic responsiveness: a dose assessment study

The clinical diagnosis of idiopathic Parkinson's disease (IPD) remains difficult and is supported by a favorable response to levodopa, while failure to respond represents an exclusion criterion. Recently, the response to subcutaneous apomorphine has been suggested as a tool in predicting levodopa responsiveness in parkinsonian syndromes. We administered apomorphine at doses of 10, 50, and 100 micrograms/kg subcutaneously against placebo over two consecutive days in 37 patients with parkinsonism and evaluated the motor response for 90 min after each dose. Subsequently, we compared the motor response with the follow-up response to levodopa therapy and to a final diagnosis. Twenty-seven patients of 37 showed a positive response to apomorphine, and 10 had a negative response. All positive responses to the apomorphine test were obtained with 50 or 100 micrograms/kg doses. Because of the high frequency of side effects with the dose of 100 micrograms/kg, 50 micrograms/kg seems more useful. After an adequate period of levodopa/carbidopa therapy (12-month follow-up), 29 patients improved; 25 of these had demonstrated a positive response to the apomorphine test. The final diagnosis of IPD, made on the basis of an exhaustive clinical and neuroradiological evaluation and on the response to chronic levodopa therapy, was in good agreement with the response to the apomorphine test (predictivity of diagnosis, 86.4%). Our data indicate that subcutaneous apomorphine at the dose of 50 micrograms/kg is a useful tool in the differential diagnosis of parkinsonian syndromes.

Subcutaneous apomorphine in Parkinson's disease: response to chronic administration for up to five years

Subcutaneous apomorphine, administered by continuous waking-day infusion with boluses, or by repeated intermittent injection, was given to 71 parkinsonian patients with severe refractory levodopa related on-off fluctuations for 1-5 years. A mean reduction in daily off period time of approximately 50% was maintained, and the incidence of neuropsychiatric toxicity remained low on long-term follow-up. No clinically significant tolerance or loss of therapeutic effect was seen, although increasingly severe on-phase dyskinesias and postural instability marred the long-term therapeutic response in many patients. Despite these drawbacks, apomorphine, when combined with the peripheral dopamine receptor agonist domperidone, represents a significant therapeutic advance in the management of late-stage Parkinson's disease and should certainly be considered before experimental implantation procedures.

Dopamine agonists in Parkinson's disease: a look at apomorphine

Apomorphine is a D1 and D2 dopamine receptor agonist with anti-parkinsonian properties qualitatively similar to those seen with L-dopa. It was first used in the treatment of Parkinson's disease by Schwab in the 1950s but owing to its short duration of action, the need for parenteral administration, and adverse reactions including nausea, vomiting, postural hypotension and sedation, it was not widely prescribed. In the early 1970s, Cotzias confirmed its potent anti-parkinsonian effects and that some of its secondary effects were diametrically opposite to those seen with L-dopa. The advent of peripheral dopamine receptor antagonist drugs, which counteract the unwanted effects of apomorphine, and the development of new drug delivery systems including insulin pens and ambulatory mini pumps have led to the resurrection of apomorphine for the treatment of Parkinson's disease. Over the last five years in Europe, the drug has proved to be a major advance in the treatment of refractory "on-off" oscillations in Parkinson's disease. It has also been used as a diagnostic test for dopaminergic responsiveness in Parkinson syndromes and tremors of uncertain aetiology. The drug has also proved particularly useful in dealing with certain "off-period" disabilities, including pain, bladder dysfunction, dystonia and gastro-intestinal symptoms. Continuous steady state infusion of apomorphine by mini-pump may reduce the severity of "on" phase dyskinesias over time. The drug has also proved useful in the clinical pharmacological investigation of the pathophysiology of the motor response to dopaminergic drugs in Parkinson's disease and the occurrence of involuntary movement sequences. Neuropsychiatric side-effects are relatively infrequent when compared with ergolene dopamine agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired activation of the supplementary motor area in Parkinson's disease is reversed when akinesia is treated with apomorphine

Using positron emission tomography (PET) we previously showed that activation of the putamen, supplementary motor area, and cingulate cortex is impaired in patients with Parkinson's disease (PD) when they are off treatment and perform volitional motor tasks. Evidence suggests that these areas are involved in the generation of internally cued movements in normal subjects. We have now studied the effect of the dopamine agonist apomorphine on cerebral activation when used to treat the akinesia of PD. Regional cerebral blood flow was measured using C15O2 PET in PD patients at rest and when performing paced joystick movements with the right hand in one of four freely chosen directions. All patients used apomorphine regularly, and were studied before treatment, while still "off" but receiving a subcutaneous apomorphine infusion, and when switched "on" with apomorphine. Significant increases in regional cerebral blood flow were determined using statistical parametric mapping. Under resting conditions apomorphine had no effect on focal or global cerebral blood flow. Seven patients with PD performed the motor task adequately in the "off" and "on" states. This group of subjects demonstrated impaired activation of the supplementary motor area and contralateral putamen in the "off" state. Activation of the supplementary motor area significantly improved when the akinesia was reversed with apomorphine. We conclude that the concomitant improvement of supplementary motor area activation and motor function in apomorphine-treated patients with PD provides further evidence for the role of this structure in generating motor programs.

Cardiovascular reflexes in Parkinson's disease: effect of domperidone and apomorphine

Cardiovascular reflexes were evaluated in 18 patients with idiopathic Parkinson's disease who had a Hoehn & Yahr score of III-IV. The effect of apomorphine and domperidone on blood pressure, heart rate, R-R interval variation, and the Valsalva ratio were studied. Autonomic dysfunction was not found in the patients and there were no differences between subgroups of patients on different treatments. Apomorphine altered cardiovascular reflexes to a greater degree in patients who received the drug for the first time than in chronically treated patients. The changes were antagonized by domperidone, a peripheral dopamine receptor antagonist. Apomorphine treated patients who were receiving long-term domperidone had similar abnormalities of cardiovascular reflexes to those who had been able to withdraw it.

The clinical use of apomorphine in Parkinson's disease

Our 2-year experience in the therapeutic use of subcutaneous apomorphine has involved 25 patients with Parkinson's disease, 10 of whom continue to use it chronically. On the basis of this experience, we have formulated certain indications for its use, together with suggested approaches to modify patients' oral drug regimes so that apomorphine can best be deployed to improve their quality of life.

Sublingual apomorphine solution in Parkinson's disease

OBJECTIVE

To compare the effects of single doses of oral levodopa, subcutaneous apomorphine and sublingual apomorphine.

DESIGN

Single-blind placebo-controlled comparative study.

SETTING

Subjects were admitted as day patients to the neurology ward.

PATIENTS

Five patients with idiopathic Parkinson's disease and "end of dose deterioration" entered and completed the study.

INTERVENTIONS

Patients were given domperidone (20 mg by mouth three times a day) to prevent nausea and apomorphine (1-3 mg by subcutaneous injection), apomorphine in glycerol (10-30 mg sublingually) or their usual levodopa regimen.

MAIN OUTCOME MEASURES

Efficacy, time to onset of effect and duration of effect of oral levodopa, subcutaneous apomorphine and sublingual apomorphine. Tremor amplitude and timed pegboard and gait tasks were used as objective indices of clinical state.

RESULTS

Maximal efficacy of the three treatments was comparable (P = 0.28-0.99). Mean latency to onset of effect of both formulations of apomorphine was less than that of levodopa (P = 0.022-0.048) but so was the duration of effect (P = 0.044-0.049).

CONCLUSIONS

Sublingual apomorphine may be a convenient means of rapidly terminating "off" periods associated with long term levodopa therapy.

Subcutaneous apomorphine increases regional cerebral blood flow in parkinsonian patients via peripheral mechanisms

1. We have measured regional cerebral blood flow (rCBF) and motor function before and after the subcutaneous (s.c.) injection of apomorphine in parkinsonian patients deprived of their usual treatment for at least 48 h. 2. Nineteen patients, pretreated with domperidone (20 mg three times daily for 48 h), received a mean dose of 5.8 mg s.c. apomorphine. All patients switched 'on'. The mean motor score was significantly improved (-65%, P less than 0.01) but no significant change in rCBF was observed. 3. Seven other patients, not pretreated with domperidone, received a lower dose (0.3 mg) of s.c. apomorphine. No change in motor score was observed while the mean rCBF significantly increased (+12%, P less than 0.05). 4. We conclude that s.c. apomorphine increases rCBF in parkinsonian patients. This effect is independent of the central therapeutic effects of the drug. It is mediated by the stimulation of dopaminergic receptors of the cerebral vessels. These receptors are located outside the cerebral blood brain barrier and can be considered as 'peripheral' ones.

Absorption of apomorphine by various routes in parkinsonism

We wanted to determine the absorption and clinical effect of sublingual (SL) and transdermal apomorphine in parkinsonism. Patients received single SL apomorphine doses (N = 7) and the absorption was compared with parenteral (N = 5) and oral (N = 4) doses. One patient received a transdermal dose of apomorphine. The relative bioavailability of SL apomorphine ranged from 10 to 22% of a parenteral apomorphine dose. Oral apomorphine was less than 4% bioavailable, and the transdermal dose did not produce detectable plasma levels. Three patients with motor fluctuations responded to SL apomorphine, with a latency to effect of 20-40 min and a duration of effect of 15-100 min. One patient used SL apomorphine as an adjunct with levodopa, and during 1 month reported a large decrease in "off" periods. We conclude that apomorphine is effectively absorbed by the sublingual route.

The short-duration response to apomorphine: implications for the mechanism of dopaminergic effects in parkinsonism

The pharmacological basis of the short-duration response to dopaminergic stimulation in parkinsonism is not completely understood. Whereas it is generally assumed that the response reflects concurrent dopamine receptor occupancy, it is also possible that receptor activation triggers events that outlast the time that receptors are occupied by agonist. To distinguish between these two possibilities, we administered apomorphine, a mixed D1-D2 agonist with rapid equilibration between plasma and brain, to patients with parkinsonism. The clinical response to apomorphine injections lagged behind peak plasma concentrations and persisted beyond the time plasma concentrations following ineffective doses. We conclude that dopaminergic stimulation triggers effects that outlast the period of receptor occupancy by agonist. Understanding these steps may offer new pharmacological therapies for parkinsonism.

Subcutaneous apomorphine in the treatment of Parkinson's disease

Apomorphine a dopamine receptor agonist was given subcutaneously to 57 levodopa treated parkinsonian patients with refractory off-period disabilities for a median period of 16 months. In 30 given intermittent suprathreshold injections the mean number of hours spent in a disabling off state fell from 6.9 to 2.9. Similar benefit was observed in 21 patients receiving continuous infusions with additional boluses on demand by mini-pump (mean reduction of hours off from 9.9 to 4.5). Twelve patients have been treated for over two years without tachyphylaxis or loss of response. The incidence of neuropsychiatric side-effects has been low (7%). Six patients failed to show a sustained worthwhile response; severe disabilities during "on" periods being the major problem. Subcutaneous apomorphine is proposed as an effective treatment for patients with incapacitating "off" period disabilities refractory to oral medication and should be considered before experimental implantation procedures.

Peripheral pharmacokinetics of apomorphine in humans

Apomorphine, a potent dopamine agonist, has been used in acute and chronic studies of parkinsonism and other neurological disorders. To define its peripheral pharmacokinetics, we administered apomorphine by subcutaneous injection, by subcutaneous infusion, and by intravenous infusion to 15 patients with parkinsonism and measured plasma apomorphine levels by high-performance liquid chromatography with electrochemical detection. The peak drug levels and area under the curve were closely correlated with the dose administered; time to peak was brief and was independent of dose. The variation in absorption was high between subjects but low within individual subjects. In 11 of 15 subjects, the disappearance of drug could be described by a two-compartment model, with a distribution half-life of 5 minutes and an elimination half-life of 33 minutes. The drug absorption, volume of distribution, plasma clearance, and half-lives were similar for subcutaneous injection, subcutaneous infusion, and intravenous infusion. We conclude that apomorphine is rapidly and completely absorbed from subcutaneous tissue, correlating with the rapid onset of clinical effects, and that the brief duration of clinical action of the drug is explained by its rapid clearance.

Apomorphine: clinical studies on erectile impotence and yawning

1. The erectile response to the short-acting dopamine (DA) receptor agonist, apomorphine (Apo) HCl (0.25, 0.5, 0.75 and 1.0 mg sc), and placebo was evaluated in 28 impotent patients and penile circumference monitored using a mercury strain gauge and strip chart recording. 2. A full erection (increment in penile circumference greater than 2 cm and lasting at least one minute) occurred in 17 patients with Apo; no erection developed after placebo. An erection occurred in 6/8 patients with impaired glucose tolerance, 2/6 patients with diabetes mellitus and in both patients on lithium. 3. Nine patients who responded to Apo were treated in an open trial with bromocriptine; 6 reported improvement in potency. 4. Impairment in DA function may play a role in idiopathic impotence and in impotence associated with impaired glucose tolerance and diabetes mellitus. 5. An erectile response to Apo may predict therapeutic response to bromocriptine or other long acting dopaminergic agents. 6. Lithium, which inhibits DA-sensitive adenylate cyclase, does not prevent Apo-induced erections. This provides further support indicating that Apo induces erections by an effect on D2 receptors. 7. The yawning response to placebo and four doses of Apo HC1 (3.5, 5.0, 7.0, and 10.5 ug/kg sc) was evaluated in five normal men using a polygraphic technique. The yawning response was also assessed in normal young (less than 30 yrs; N = 16) and elderly (greater than 60 yrs; N = 12) volunteers. 8. Under experimental conditions of study, placebo induced spontaneous yawning. This was antagonized by 3.5 and 5.0 ug/kg Apo HC1 but increased by 7.0 ug/kg Apo HC1. These observations are compatible with the view that Apo HC1 in doses of 3.5-5.0 ug/kg stimulates presynaptic DA receptors whereas 7.0 ug/kg stimulates postsynaptic DA receptors. 9. Spontaneous and Apo-induced yawning were significantly decreased in the elderly which suggests that D2 receptor function declines with normal aging.

Role of subcutaneous apomorphine in parkinsonian voiding dysfunction

Ten patients with Parkinson's disease and urinary symptoms underwent urodynamic assessments before and after subcutaneous administration of the dopamine receptor agonist apomorphine. Voiding efficiency improved after apomorphine injection, with an increase in mean and maximum flow rates in nine patients and reduction in post-micturition residual volume in six. Although the effect on detrusor behaviour was variable, subcutaneous apomorphine may be of use in both the assessment and treatment of voiding dysfunction in patients with Parkinson's disease.

Subcutaneous apomorphine in parkinsonian on-off oscillations

Subcutaneous apomorphine, a dopamine agonist, was given by continuous infusion during the day or by repeated injections to 19 patients with Parkinson's disease disabled by severe on-off fluctuations. All patients were also given domperidone. The 11 patients treated by infusion showed marked and sustained improvement, and their mean duration of daily off periods over a period of 15 months fell by 6.3 h; similar results were obtained in 8 patients with less severe disabilities who were given repeated apomorphine injections. The therapeutic response to apomorphine was similar to that seen with intravenous levodopa; in patients treated by infusion the mean daily levodopa dose was reduced by 209 mg. These results confirm that during off periods dopamine receptors remain responsive to stimulation and provide evidence of a new, effective, and well-tolerated treatment for the most disabling complication of long-term levodopa therapy.

Apomorphine in the evaluation of dopaminergic function in man

1. Apomorphine (Apo), a short acting dopamine (DA) receptor agonist, stimulates growth hormone (GH) secretion, decreases prolactin secretion, induces yawning, penile erections and other physiological effects in man. An effect on behavior, movement disorders and alcoholism has also been described. 2. Apo-mediated responses are used to evaluate DA function in psychiatric and neurological disorders. Many of the studies in schizophrenia using the GH response to Apo as an index of central DA function are difficult to interpret because of failure to control for key variables. 3. The GH response to Apo is a useful system to evaluate the effects of various drugs including peptides which may not cross the blood brain barrier on DA function in man. 4. Apo is a potent sedative. Specific antimanic, antischizophrenic, and anticraving effects in alcoholics have not been convincingly demonstrated. Side effects of Apo and failure to use active placebo make double-blind studies difficult. 5. Apo improves parkinsonian symptoms and certain forms of reflex epilepsy but beneficial effects in other involuntary movement disorders requires further documentation. 6. Apo may be a useful agent to evaluate DA function in impotent patients and predict a therapeutic response to long-acting dopaminergic agents. 7. Impairment of DA function may play a role in diabetic impotence. 8. The development of a simple polygraphic method to monitor the yawning response to Apo may facilitate clinical studies on the basic physiology of yawning in man and the use of the yawning response as a measure of central DA function in schizophrenia and other clinical disorders. 9. The use of Apo with 18F-fluorodeoxyglucose positron emission tomography to examine regional DA function in man opens up a promising area of research. 10. Though long-acting orally active aporphine DA agonists and antagonists have been developed the problem of tolerance may limit their therapeutic potential.

Domperidone antagonizes bromoergocriptine--induced nausea and vomiting without affecting its inhibition of prolactin secretion in puerperal women

In the present study, 122 post puerperal women received at random bromoergocriptine, domperidone, bromoergocriptine plus domperidone or placebo treatment. Domperidone started 20-24 h after delivery and given for 10 or 15 days did not antagonize either the decrease in serum PRL induced by bromoergocriptine or the inhibition of lactation. It did suppress nausea and vomiting in the patients. The results are compatible with the idea that domperidone binds with a higher affinity than bromoergocriptine to DA (dopamine) receptors in the area postrema or the stomach. The converse phenomenon occurs at the level of the DA receptors on the PRL- secreting cells of the anterior pituitary gland.

A simple method for the study of yawning in man induced by the dopamine receptor agonist, apomorphine

Apomorphine (Apo), a dopamine (DA) receptor agonist, induces yawning by stimulating central DA autoreceptors. Few data are available on Apo-induced yawning in man. A simple method for recording and measuring Apo-induced yawning by measuring the displacement of the lower jaw using a pair of linearlized magnetometers with one sensor attached to the forehead just below the hairline and the other under the chin is described. The output of the magnetometers is fed into a DC amplifier and displayed on a strip chart recorder. Complete concordance between evaluators reading the tracings and between observed yawning and recorded yawns was found. Measuring Apo-induced yawning may provide a simple approach to evaluating DA autoreceptor function in normal subjects and in patients with psychiatric and neurological disorders. Preliminary data show that Apo-induced yawning is more marked in women than in men. This is in contrast to spontaneous and drug-induced yawning in animals which is predominantly a male phenomenon. Sleep appears to inhibit Apo-induced yawning.

Domperidone. A review of its pharmacological activity, pharmacokinetics and therapeutic efficacy in the symptomatic treatment of chronic dyspepsia and as an antiemetic

Domperidone is a dopamine antagonist that does not readily enter the central nervous system. Given parenterally or orally it increases gastric emptying of liquids and increases lower oesophageal sphincter pressure in healthy subjects. The antiemetic and pharmacodynamic profile of domperidone is similar to that of metoclopramide, although domperidone has a lower propensity to cause extrapyramidal side effects. Domperidone effectively alleviates symptoms of chronic postprandial dyspepsia and nausea and vomiting due to a wide variety of underlying causes and in some studies has been superior to metoclopramide. Vomiting associated with the administration of moderately emetic cytotoxic drugs is controlled in the majority of patients. Alleviation of the dose-limiting peripheral side effects (nausea and vomiting) of the anti-Parkinsonian drugs bromocriptine and levodopa, enables a higher optimum dose, with consequent improvement in Parkinsonian symptoms. Domperidone does not aggravate the extrapyramidal side effects of neuroleptic drugs. Control of cytotoxic-induced, and postprandial nausea and vomiting in children has been achieved with domperidone without evidence of extrapyramidal side effects. Indeed, side effects have seldom occurred with therapeutic doses of domperidone.

Domperidone. A review of its pharmacological activity, pharmacokinetics and therapeutic efficacy in the symptomatic treatment of chronic dyspepsia and as an antiemetic

Domperidone is a dopamine antagonist that does not readily enter the central nervous system. Given parenterally or orally it increases gastric emptying of liquids and increases lower oesophageal sphincter pressure in healthy subjects. The antiemetic and pharmacodynamic profile of domperidone is similar to that of metoclopramide, although domperidone has a lower propensity to cause extrapyramidal side effects. Domperidone effectively alleviates symptoms of chronic postprandial dyspepsia and nausea and vomiting due to a wide variety of underlying causes and in some studies has been superior to metoclopramide. Vomiting associated with the administration of moderately emetic cytotoxic drugs is controlled in the majority of patients. Alleviation of the dose-limiting peripheral side effects (nausea and vomiting) of the anti-Parkinsonian drugs bromocriptine and levodopa, enables a higher optimum dose, with consequent improvement in Parkinsonian symptoms. Domperidone does not aggravate the extrapyramidal side effects of neuroleptic drugs. Control of cytotoxic-induced, and postprandial nausea and vomiting in children has been achieved with domperidone without evidence of extrapyramidal side effects. Indeed, side effects have seldom occurred with therapeutic doses of domperidone.

Effect of domperidone on apomorphine-induced growth hormone secretion in normal men

Domperidone, a peripheral dopamine (DA) receptor blocker which poorly crosses the blood-brain barrier and which is inactive towards dopamine-sensitive adenylate cyclase, in a dose (100 micrograms/kg) sufficient to increase serum prolactin levels at least 5-fold, decreased the growth hormone (GH) response to the DA receptor agonist, apomorphine HCI (Apo) (0.5 gm s.c.) in each of six normal men examined. The mean GH increment at 30, 45, 60 and 75 min following Apo injection, the mean individual peak increment and the mean individual GH secretion (ng min) was significantly decreased by domperidone pretreatment (p less than 0.005 -p less than 0.002). These results indicate that in man Apo stimulates GH secretion by an effect on DA receptors which are not linked to adenylate cyclase and which are situated at a locus in the hypothalamic-pituitary axis that lies outside the blood-brain barrier.

Dopamine autoreceptor stimulation: clinical significance

Recent studies of the effects of low doses of dopamine agonists, designed to stimulate dopamine autoreceptors and hence diminish the synthesis and release of dopamine, were based on a series of basic research studies which demonstrated the existence of autoreceptors on dopamine neurones of the nigrostriatal, mesolimbic and mesocortical dopaminergic neurones. Evidence for autoreceptors on the tuberoinfundibular dopamine neurones which participate in the regulation of prolactin and growth hormone secretion is lacking. Some recent reports have questioned the existence of dopamine autoreceptors on the mesolimbic and nigrostriatal dopamine neurones. Specificity of various dopamine agonists and antagonists for the dopamine autoreceptor will be reviewed. The sedative, anxiolytic, antipsychotic, antidyskinetic and neuroendocrine effects of low dose dopamine agonists in man will be described. Low dose apomorphine, N-propylapomorphine and bromocriptine have been reported to have antipsychotic effects in the major psychoses, to diminish tardive dyskinesia and to enhance extrapyramidal insufficiency. A unique depressive state which developed in a small proportion of psychiatric patients after low dose apomorphine will be described. Further evidence for the lack of dopamine autoreceptors on the tuberoinfundibular dopamine neurones in man will be presented. Strategies for further study of the dopamine autoreceptor concept in man will be discussed.

Dopamine and antianxiety activity

Clinical trials have indicated that buspirone (Buspar) is effective in the treatment of anxiety with efficacy and dosage comparable to diazepam. Until recently it has been thought that antianxiety drugs must alter benzodiazepine receptor binding in vitro. However, buspirone lacks any structural similarity to te benzodiazepines and does not interact with the benzodiazepine/gamma-aminobutyric acid (GABA) axis. Specifically, buspirone neither stimulates nor inhibits [3H]benzodiazepine binding, does not affect the influence o GABA or halide anions on benzodiazepine binding, and does not interfere with GABA binding or uptake. Behavioral testing has revealed that buspirone does not produce muscle weakness, does not control seizures, does not potentiate the impairment of psychophysiological function or lethality produced by administration of CNS depressants, does not produce sedation/hypnosis and does not appear to possess any abuse potential or liability for physical dependence. Thus, buspirone has been termed an anxioselective agent. Buspirone appears to only interact with the dopaminergic system with reasonable potency and exhibits properties of both a dopamine agonist and a dopamine antagonist. This suggests that dopamine is implicated in the etiology and expression of anxiety. A discussion of this implication is presented with a review of the clinical efficacy of nonbenzodiazepine drugs, especially dopamine agonists and dopamine antagonists, in the management of anxiety. In addition, neuropharmacological studies which have investigated the role of dopamine in animal models of anxiety are considered. Finally, the multiplicity of dopamine receptors and their regional localization in the brain are considered in the formulation of an hypothesis which features a role for the dopaminergic agents in the pharmacotherapy of anxiety.

Differential effects of ageing on distinct features of apomorphine stereotypy in the adult rat

Locomotor features of stereotypy induced by 0.15 mg/kg of subcutaneous apomorphine increased over the age ranges of 2.5-8 and 8-10 months in the adult rat. Perioral features of stereotypy induced by 1 mg/kg of apomorphine, and spontaneous activity did not show age-dependent changes. Heterogeneous features of apomorphine stereotypy may have distinct physiological substrates that are differentially sensitive to parameters of maturation and ageing.