Deprenyl in the treatment of symptom fluctuations in advanced Parkinson's disease

Pharmacokinetic optimisation in the treatment of Parkinson's disease

The current symptomatic treatment of Parkinson's disease mainly relies on agents which are able to restore dopaminergic transmission in the nigrostriatal pathway, such as the dopamine precursor levodopa or direct agonists of dopamine receptors. Ancillary strategies include the use of anticholinergic and antiglutamatergic agents or inhibitors of cerebral dopamine catabolism, such as monoamine oxidase type B inhibitors. Levodopa is the most widely used and effective drug. Its peculiar pharmacokinetics are characterised by an extensive presystemic metabolism, overcome by the combined use of extracerebral inhibitors of the enzyme aromatic-amino acid decarboxylase and rapid adsorption in the proximal small bowel by a saturable facilitated transport system shared with other large neutral amino acids. Drug transport from plasma to the brain is mediated by the same carriers operating in the intestinal mucosa. The main strategies to assure reproducibility of both drug intestinal absorption and delivery to the brain and clinical effect include standardisation of levodopa administration with respect to meal times and a controlled dietary protein intake. The levodopa plasma half-life is very short, resulting in marked plasma drug concentration fluctuations which are matched, as the disease progresses, with swings in the therapeutic response ('wearing-off' phenomena). 'Wearing-off' phenomena can be also associated, at the more advanced disease stages with a 'negative', both parkinsonism-exacerbating and dyskinetic effect of levodopa at subtherapeutic plasma concentrations. Dyskinesias may be also related to high-levodopa, excessive plasma concentrations. Recognition of the different levodopa toxic response patterns can be difficult on a clinical basis alone, and simultaneous monitoring of levodopa concentration-effect relationships may prove useful to disclose the underlying mechanism and in planning the correct pharmacokinetic management. Controlled-release levodopa formulations have been developed in an attempt to smooth out fluctuations in plasma profiles and matched therapeutic responses. The delayed levodopa absorption and lower plasma concentrations which characterise controlled-release formulations compared with standard forms must be taken into account when prescribing dosage regimens and can be complicating factors in the management of the advanced disease stages. The pharmacokinetic and pharmacodynamic characterisation of the other antiparkinsonian agents is hampered by the lack of sensitive and specific analytical methods to measure their very low plasma drug concentrations and by the difficulty in quantitatively assessing overall moderate drug clinical effects. In clinical practice an optimal dosage schedule is still generally found for each patient on an empirical basis. Future strategies should focus on the search for pharmacological agents with a better kinetic profile, particularly a higher and reproducible bioavailability and a predictable relationship between plasma drug concentration and clinical response. Treatments aimed not only at controlling the symptoms, but also at slowing the neurodegenerative process, are currently under intensive investigation.

Deprenyl in the treatment of Parkinson's disease: clinical effects and speculations on mechanism of action

Selegiline is a relatively selective inhibitor of monoamine oxidase type B that has been used in Parkinson's disease as an adjunct to levodopa and as putative neuroprotective therapy. Clinical trials demonstrate that selegiline slows the rate of disease progression and delays the appearance of disability necessitating levodopa. However, confounding symptomatic effects have made it difficult to ascertain the presence of any direct neuroprotective effect. Laboratory studies demonstrate that selegiline protects dopaminergic neurons through a mechanism that does not involve MAO-B inhibition. Recent studies suggest that neuroprotection in laboratory models may be related to the capacity of selegiline to up-regulate a series of anti-oxidant and anti-apoptotic molecules which promote cell survival. Further delineation of the precise mechanism whereby selegiline induces this effect may permit for the development of enhanced neuroprotective benefits in PD patients.

Antioxidant mechanism and protection of nigral neurons against MPP+ toxicity by deprenyl (selegiline)

The current research has demonstrated that MPP+ can induce lipid peroxidation in the nigrostriatal system of rat in vivo. Antioxidant agent U-78517F and .OH scavenger DMSO may protect against MPP+ toxicity through the inhibition of .OH radical-mediated oxidative injury in the substantia nigra. These findings indicate that the cytotoxic hydroxyl radical generated from dopamine oxidation in the iron-rich basal ganglia may contribute to the mechanism underlying the selective A9 melanized nigral degeneration in MPTP-Parkinsonism and possibly in idiopathic Parkinson's disease. In addition, the present studies also clearly demonstrate that deprenyl can substantially protect dopaminergic neurons against MPP+ toxicity in the substantia nigra zona compacta in vivo. The neuroprotective effect provided by deprenyl may not be the consequence of its inhibition of MAO-B activity or prevention of the uptake of MPP+ by dopaminergic neurons. A unique antioxidant property of deprenyl by suppressing .OH formation and associated oxidative injury induced by MPP+ may contribute to the apparent neuroprotective action. In perspective, this putative antioxidant effect of deprenyl may provide another mechanism to its overt neuroprotective effects against oxygen radical-mediated oxidative injury in some neurotoxic chemicals, such as 6-OHDA and DSP-4, and probably in Alzheimer's disease and senescent changes. Finally, based on the present data, a possible neuroprotective therapeutic window of deprenyl in the treatment of early Parkinson's disease has been proposed. It is suggested that deprenyl should be introduced as early as possible in de novo Parkinsonian patients to achieve its full neuroprotective effect on nigral degeneration. Moreover, a combination of early detection of individuals at risk of developing Parkinson's disease and early intervention of deprenyl and/or other centrally active antioxidants to these patients may provide a new preventive therapeutic strategy in the future, in addition to the current conventional levodopa treatment of Parkinson's disease.

Chronic treatment of aged mice with L-deprenyl produces marked striatal MAO-B inhibition but no beneficial effects on survival, motor performance, or nigral lipofuscin accumulation

Male C57BL/6J mice were provided I-deprenyl (at 0, 0.5 mg/kg or 1.0 mg/kg per day) in their drinking water beginning at 18 months of age. A battery of motor tests, including open-field, tightrope, rotorod, inclined screen, runwheel, and rotodrum tests, was administered before treatment and then 6 months later at 24 months of age. A subsample of mice was retested again at 27 months of age. An untreated group of 9-month-old mice served as young controls. Deprenyl treatment reduced striatal MAO-B activity by up to 60% after 6 months on treatment but had no significant effects on striatal catecholamine levels. No significant effects of deprenyl treatment were observed on body weight, fluid intake, or survival of the mice. Chronic deprenyl treatment also did not affect motor performance in any test, except rotodrum performance at 27 months of age, which was significantly better in the 1.0 mg/kg group treated group compared to controls. No age or deprenyl effects were observed with respect to cell counts in the substantia nigra. However, nigral cells containing lipofuscin increased with age, but this neurohistochemical parameter was also unaffected by deprenyl treatment.

The effects of deprenyl on methamphetamine-induced dopamine depletions

The effects of deprenyl on methamphetamine-induced dopamine depletions were studied in mice. Four SC injections of 12.5 mg/kg of methamphetamine at two-hour intervals caused substantial (72-82%) and long-lasting depletions of striatal dopamine. Pretreatment with either 25 or 40 mg/kg of deprenyl did not significantly alter the magnitude of this depletion. These results indicate that, unlike what is observed following MPTP, there is no protection afforded dopaminergic cells by deprenyl pretreatment in the methamphetamine model of parkinsonism.

The new generation of monoamine oxidase inhibitors

Irreversible and unspecific inhibitors of MAO were the first modern antidepressants, but after an initial success they fell into discredit due to adverse side effects. In the past two decades interest in MAO inhibitors has been renewed because of progress in basic research, a milestone being the finding that there are two subtypes of MAO, MAO-A and MAO-B. These are distinct proteins with high amino acid homology, coded by separate genes both located on the short arm of the human chromosome X. The enzyme subforms show different substrate specificities in vitro and different distributions within the central nervous system and in peripheral organs. In the central nervous system of man MAO-A seems to be mainly involved in the metabolism of 5 HT and noradrenaline, whereas 2-phenylethylamine and probably dopamine are predominantly deaminated by MAO-B. In the intestinal tract tyramine is mainly metabolized by MAO-A. These characteristics indicate distinct physiological functions of the two MAO-subforms. Several irreversible and reversible non-hydrazine inhibitors with relative selectivities for one of the MAO-subforms have been developed. They belong to various chemical classes with different modes of enzyme inhibition. These range from covalent mechanism based interaction (e.g. by propargyl- and allylamine derivatives) to pseudosubstrate inhibition (e.g. by 2-aminoethyl-carboxamides) and non-covalent interaction (e.g. by brofaromine, toloxatone and possibly moclobemide). The most important pharmacological effects of the new types of MAO inhibitors are those observed in neuropsychiatric disorders. The inhibitors of MAO-A show a favorable action in various forms of mental depression. The drugs seem to have about the same activity as other types of antidepressants, including tricyclic and related compounds as well as classical MAO inhibitors. The onset of action of the MAO-A inhibitors is claimed to be relatively fast. Other possible indications of these drugs include disorders with cognitive impairment, e.g. dementia of the Alzheimer type. In subjects with Parkinson's disease the MAO-B inhibitor L-deprenyl exerts a L-dopa-sparing effect, prolongs L-dopa action and seems to have a favorable influence regarding on-off disabilities. The action is in general transitory (months to several years). In addition L-deprenyl has been shown to delay the necessity for L-dopa treatment in patients with early parkinsonism. Whether the drug influence the progression of the disease is still a matter of debate. L-deprenyl also appears to have some antidepressant effect (especially in higher doses) and to exert a beneficial influence in other disorders, e.g. dementia of the Alzheimer type.(ABSTRACT TRUNCATED AT 400 WORDS)

Brain monoamine oxidase and aging: A review

The present state of research on the age-related dynamics of brain monoamine oxidase (MAO) activity and its role in the development of age pathology is described. Special attention is given to the role of MAO in the pathogenesis of parkinsonism and to the mechanisms of its interaction with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a possible etiological factor of parkinsonism development in aging. The mechanisms of action of the selective MAO-B inhibitor, deprenyl, and their peculiarities in old age are analyzed. This study provides evidence pointing to a need for the use of deprenyl in geriatric practice as an effective drug for parkinsonism treatment and as a potent geroprotector.

Determination of an irreversible inhibitor of monoamine oxidase B (MDL 72974A) in human plasma and urine by gas chromatography-positive-ion chemical ionization mass spectrometry

A sensitive and specific assay has been developed for the quantitative measurement in human plasma and urine of the irreversible inhibitor of monoamine oxidase B [(E)-4-fluoro-beta-fluoromethylenebenzene-butanamine HCl salt] (MDL 72974A) (I). This assay is based on gas chromatography-mass spectrometry with ammonia as the chemical ionization reagent gas. After addition of 1-fluoro-2-(4-chlorobenzene)-ethanamine HCl salt (MDL 71946A) as the internal standard, plasma (1 ml) and urine (100 microliter) samples were extracted using an automated solid-liquid extraction procedure on CN columns. The eluent was dried with a stream of nitrogen, and the residue was derivatized with pentafluoropropionic anhydride. Selected-ion monitoring of the [MNH4]+ ions m/z 361 (I) and 351 (internal standard) was used for quantification. The method yielded a linear response over the concentration range 0.25-100 pmol/ml in plasma with a limit of quantitation of 0.25 pmol/ml. The within-day reproducibility at a concentration of 5 pmol/ml was 4.6% and at a concentration of 50 pmol/ml was 1.3%. The day-to-day reproducibility was 5.2 and 7.0% at concentrations of 10 and 30 pmol/ml, respectively. The method was applied to the quantification of I in plasma and urine after the administration of 12-mg doses of I to a healthy male volunteer.

Experience with selegiline and levodopa in advanced Parkinson's disease

We compared the results of treatment with selegiline (deprenyl, Eldepryl) in 17 patients with advanced Stage 4 Parkinson Disease (PD) who were on levodopa (as Sinemet) with 65 Stage 2 or 3 patients with early PD who were also on levodopa. The first group consisted of 17 patients with advanced Stage 4 PD without response fluctuations ("wearing off" or "on off" phenomena). Their mean age was 72.1 +/- 7.5 years, their mean duration of PD was 7.4 +/- 3.2 years. The second group consisted of 65 patients with Stage 2 or 3 PD who had recently been started on levodopa. Their mean age was 63 +/- 12.1 years, their mean duration of PD was 7.4 +/- 3.2 years. The mean dose of selegiline was 10.0 +/- 1.8 mg per day (range 5-20 mg). The mean duration of treatment was 1.5 +/- 0.8 years. During the four years of observation 55.3 +/- 8.0% of the Stage 2 or 3 patients improved while only 14.3 +/- 13.5% of the Stage 4 patients improved. This difference was significant (p less than 0.05). During this time 22.0 +/- 6.7% of the Stage 2 or 3 patients worsened and 60.7 +/- of the Stage 4 patients worsened. This degree of worsening was significant (p less than 0.05). Adverse effects were minor and reversible. Our observations suggest that selegiline is more effective (higher percent of patients improving, lower percent of patients worsening) when it is added earlier with patients on levodopa than when it is added later.

Selegiline. A review of its pharmacology, symptomatic benefits and protective potential in Parkinson's disease

Selegiline (deprenyl) is a selective inhibitor of cerebral monoamine oxidase type B at the dosage (10 mg/day) used in patients with Parkinson's disease. Through this activity, the drug increases nigrostriatal dopamine levels, and may protect neurons against damage by free radicals and possibly exogenous neurotoxins. Selegiline also inhibits dopamine reuptake from the synaptic cleft. Because of its selectivity, selegiline 10mg daily does not prevent the breakdown and exacerbate the indirect pressor effects of dietary amines such as tyramine; it is devoid of the 'cheese' effect. Following oral administration, selegiline is rapidly metabolised to L-methamphetamine and L-amphetamine, which may account for the euphoria and insomnia seen in many patients, although potentiation of dopaminergic activity with concurrent levodopa appears more likely. The drug is a useful adjunct to levodopa in Parkinsonism, improving 'end-of-dose' fluctuations, producing modest improvements in motor function, and allowing a reduction in levodopa dosage. Indeed, if levodopa dosages are not decreased when selegiline is added to the therapeutic regimen, peak concentration dyskinesias due to levodopa are often exacerbated. However, symptomatic benefits are rarely maintained for more than a year and selegiline is relatively ineffective in allaying the abrupt swings in response to levodopa ('on/off' effects). When used alone in patients with mild disease, selegiline appears to slow the rate of symptom progression and may extend survival, through either neuroprotection or symptom relief. Whichever mechanism(s) is responsible, there is strong evidence to suggest that selegiline should be considered both in patients newly diagnosed with Parkinson's disease in an attempt to delay symptom progression, and in those experiencing dose-dependent fluctuations in response to levodopa.

Selegiline: initial or adjunctive therapy of Parkinson's disease?

Parkinson's disease (PD) is a progressive neurologic motor disorder. Currently, levodopa/carbidopa is the standard mode of therapy for PD; however, it does not prevent progression of the disease. Selegiline (also known as deprenyl), is a selective irreversible monoamine oxidase type B inhibitor virtually devoid of the tyramine reaction at the recommended dosage of 10 mg/d. It is approved by the Food and Drug Administration for the adjunctive use in the management of patients with PD who are receiving levodopa/carbidopa and exhibit a "wearing off" effect of levodopa. Numerous clinical trials have been conducted evaluating selegiline's role in the treatment of PD. Preliminary evidence from the DATATOP trial suggests that selegiline may slow the progression of PD when used as initial therapy. However, final results of this trial and additional long-term controlled trials comparing selegiline to levodopa and placebo groups are necessary to further clarify selegiline's role in the treatment of PD.

Selegiline in Parkinson's disease

Twenty patients with Parkinson's disease were treated with the MAO-B inhibitor selegiline (l-deprenyl) and placebo without levodopa (L-dopa) in a randomized double-blind clinical cross-over study to analyze relative importances of dopamine (DA) synthesis and metabolism. The daily dose of selegiline was gradually increased to a maximum of 30 mg in all patients. The clinical neurological disability (Columbia score) was about 10% less on selegiline (30 mg/day) than on placebo. This difference was neither statistically nor clinically significant. The results are compatible with the possibility that treatment with selegiline without concomitant L-dopa does not significantly increase DA concentration which remains low and is determined mainly by tyrosine hydroxylase activity. At low DA levels the DA re-uptake mechanism recaptures most of the released DA and DA deamination is of minor significance. The pathway of DA oxidation becomes more important only at higher DA concentrations, accomplished by bypassing the rate limiting step of tyrosine hydroxylation using L-dopa.

Effect of deprenyl on the progression of disability in early Parkinson's disease

In a clinical trial that is still in progress, we studied the ability of deprenyl and tocopherol, antioxidative agents that act through complementary mechanisms, to delay the onset of disability necessitating levodopa therapy (the primary end point) in patients with early, untreated Parkinson's disease. Eight hundred subjects were randomly assigned in a two-by-two factorial design to receive deprenyl, tocopherol, a combination of both drugs, or placebo, and were followed up to determine the frequency of development of the end point. The interim results of independent monitoring prompted a preliminary comparison of the 401 subjects assigned to tocopherol or placebo with the 399 subjects assigned to deprenyl, alone or with tocopherol. Only 97 subjects who received deprenyl reached the end point during an average 12 months of follow-up, as compared with 176 subjects who did not receive deprenyl (P less than 10(-8). The risk of reaching the end point was reduced by 57 percent for the subjects who received deprenyl (Cox hazard ratio, 0.43; 95 percent confidence limits, 0.33 and 0.55; P less than 10(-10]. The subjects who received deprenyl also had a significant reduction in their risk of having to give up full-time employment (P = 0.01). We conclude from these preliminary results that the use of deprenyl (10 mg per day) delays the onset of disability associated with early, otherwise untreated cases of Parkinson's disease.

New approaches in the use of selegiline for the treatment of Parkinson's disease

Selegiline hydrochloride (deprenyl) is a safe, useful adjuvant therapy in patients with Parkinson's disease treated with L-dopa. The optimum time for its introduction into the treatment regimen of a patient remains controversial. A multicentre long-term study being conducted by the Parkinson's Disease Research Group of the United Kingdom to attempt to answer whether selegiline improves the natural history of Parkinson's disease is discussed. In a separate study we have been unable to demonstrate that higher doses of selegiline (up to 40 mg a day) produce additional therapeutic benefit above the conventional dose of 10 mg a day in levodopa-treated patients with motor fluctuations. Preliminary data from a neuropsychological study is also presented which suggests that selegiline may have beneficial effects on the speed of psychomotor responses supporting the anecdotal clinical observations of increased mental energy and alacrity.

Double-blind, crossover placebo controlled trial of selegiline in Parkinson's disease--an interim analysis

The response to selegiline was assessed in ten (2 females, 8 males) idiopathic parkinsonian patients with the wearing off response. Selegiline was compared to placebo in each patient in a double blind crossover study carried out over ten months. After 16 weeks of therapy selegiline significantly prolonged response to levodopa, extending response to 3 hours (p less than 0.05) in most patients and to 4 hours (p less than 0.001) in some patients. Baseline scores (zero time: 12 hours after their previous dose of medication) were also significantly better after selegiline therapy (p less than 0.05). Selegiline did not improve peak response (1 hour after medication) to levodopa indicating that these patients were on optimum therapy prior to receiving selegiline. Adverse effects (nausea (2), dyskinesia (2), fear reaction (1) and postural dizziness (1] occurred in 5 patients during the trial.

Selegiline and levodopa in early or moderately advanced Parkinson's disease: a double-blind controlled short- and long-term study

Selegiline 10 mg per day was compared to placebo as an adjunct to levodopa treatment in this double-blind study of early or moderately advanced Parkinson's disease. Thirty-eight patients completed an initial cross-over trial comprising two treatment periods, each of eight weeks, with a four weeks' wash-out period between them. Thirty of the patients continued in a long-term, double-blind parallel trial with a mean duration of 16 months (range 6-30 months). Selegiline treatment allowed a significant reduction of the necessary daily levodopa dose in both parts of the study and of the daily dosing frequency in the long-term investigation. In spite of this reduction of levodopa dose, an improvement was noted in tremor during the short-term selegiline periods. The side-effects were slight and related to dopamine effects and disappeared after reduction of levodopa-dose. The results support the use of selegiline as an early adjunctive treatment in Parkinson's disease.

Selegiline in the treatment of daily fluctuations in disability of parkinsonian patients with long-term levodopa treatment

In order to evaluate in a double-blind manner the therapeutic efficacy of selegiline in the treatment of late-phase Parkinson's disease, 19 patients with end-of-dose type fluctuations were randomized for a double-blind cross-over trial receiving either selegiline 10 mg or placebo. Each period lasted 12 weeks. During a two week prestudy period the dose of levodopa was titrated to optimal levels. The disability was evaluated using the Columbia University Disability Scale (CUDS). The patients kept a daily diary to monitor closely the frequency and severity of their fluctuations and the side-effects of treatment. Their parkinsonian disability and all main symptoms improved significantly during selegiline treatment. The mean duration of action of a levodopa dose was significantly longer and there was significantly less daily end-of-dose and early morning akinesia during selegiline treatment. The side-effects were similar in both treatments. This double-blind study confirms the findings of earlier open studies that selegiline potentiates and prolongs the therapeutic effects of levodopa and thus its use is particularly beneficial in patients with end-of-dose type fluctuations in disability.