Effect of adding selegeline to levodopa in early, mild Parkinson's disease. Selegeline may be toxic in presence of increased dopamine concentrations

MPP(+)-induced toxicity in the presence of dopamine is mediated by COX-2 through oxidative stress

Accumulating evidence suggests that endogenous dopamine may act as a neurotoxin and thereby participate in the pathophysiology of Parkinson’s disease (PD). Cyclooxygenase-2 (COX-2) has been implicated in the pathogenesis of PD due to its ability to generate reactive oxygen species (ROS). Inhibition of COX-2 leads to neuroprotection by preventing the formation of dopamine-quinone. In this study, we examined whether dopamine mediates 1-methyl-4-phenylpyridinium (MPP⁺)-induced toxicity in primary ventral mesencephalic (VM) neurons, an in vitro model of PD, and if so, whether the protective effects of COX-2 inhibitors on dopamine mediated MPP⁺-induced VM neurotoxicity and VM dopaminergic cell apoptosis result from the reduction of ROS. Reserpine, a dopamine-depleting agent, significantly reduced VM neurotoxicity induced by MPP⁺, whereas dopamine had an additive effect on MPP⁺-induced VM neurotoxicity and VM dopaminergic cell apoptosis. However, inhibition of COX-2 by a selective COX-2 inhibitor (DFU) or ibuprofen significantly attenuated MPP⁺-induced VM cell toxicity and VM dopaminergic cell apoptosis, which was accompanied by a decrease in ROS production in VM dopaminergic neurons. These results suggest that dopamine itself mediates MPP⁺-induced VM neurotoxicity and VM dopaminergic cell apoptosis in the presence of COX-2.

Monoamine oxidase inhibitors. A perspective on their use in the elderly

Monoamine oxidase inhibitors (MAOIs) are mainly used in psychiatry for the treatment of depressive disorders and in neurology for the treatment of Parkinson's disease. While the classical, nonselective and nonreversible MAOIs, such as phenelzine and tranylcypromine, are characterised by the risk of inducing a hypertensive crisis when dietary tyramine is ingested, the selective monoamine oxidase-B (MAO-B) inhibitor selegiline (deprenyl) and, even more so, the selective and reversible monoamine oxidase-A (MAO-A) inhibitor moclobemide, are free from this potential interaction. Drug tolerability data for the elderly show that moclobemide is one of the most well tolerated compounds. Selegiline, especially when used in combination with levodopa, can cause anorexia, dry mouth, dyskinesia and, most problematic, orthostatic hypotension. For the traditional MAOIs, phenelzine and tranylcypromine, published data are insufficient to be able to give a conclusive tolerability statement regarding the use of these compounds in elderly people. Although orthostatic hypotension occurs in most patients treated with traditional MAOIs, the incidence in elderly patients with depression does not appear to be greater than that reported with tricyclic antidepressants.

Autonomic effects of selegiline: possible cardiovascular toxicity in Parkinson's disease

OBJECTIVES

The United Kingdom Parkinson's Disease Research Group (UKPDRG) trial found an increased mortality in patients with Parkinson's disease randomised to receive selegiline (10 mg/day) and levodopa compared with those taking levodopa alone. Unwanted effects of selegiline on cardiovascular regulation have been investigated as a potential cause for the unexpected mortality finding of the UKPDRG trial.

METHODS

The cardiovascular responses to a range of physiological stimuli, including standing and head up tilt, were studied in patients with Parkinson's disease receiving levodopa alone and a matched group on levodopa and selegiline.

RESULTS

Head up tilt caused selective and often severe orthostatic hypotension in nine of 16 patients taking selegiline and levodopa, but was without effect on nine patients receiving levodopa alone. Two patients taking selegiline lost consciousness with unrecordable blood pressures and a further four had severe symptomatic hypotension. The normal protective rises in heart rate and plasma noradrenaline were impaired. The abnormal response to head up tilt was reversed by discontinuation of selegiline. Drug withdrawal caused a pronounced deterioration in motor function in 13 of the 16 patients taking selegiline.

CONCLUSION

Therapy with selegiline and levodopa in combination may be associated with severe orthostatic hypotension not attributable to levodopa alone. Selegiline also has pronounced symptomatic motor effects in advanced Parkinson's disease. The possibilities that these cardiovascular and motor findings might be due either to non-selective inhibition of monoamine oxidase or to amphetamine and met-amphetamine are discussed.

Mortality associated with selegiline in Parkinson's disease. What do the available data mean?

A recent study by the Parkinson's Disease Research Group of the United Kingdom revealed higher mortality in patients with Parkinson's disease who were treated with selegiline (deprenyl) compared with those who were not. In this article, the methodological limitations of the UK study are discussed. Although several problems exist with this study, the mortality rate was correct, since the data were obtained from a verifiable source. The question then is whether or not the higher mortality rate can be ascribed to selegiline. It is difficult to find answers to this question in the study data, and we will have to wait for the study authors' final report. No other studies have reported higher mortality with selegiline. However, when prescribing selegiline in patients with early-stage Parkinson's disease, it is important to provide them with all the available information so that treatment decisions can be made jointly. Meanwhile, the best indication for selegiline appears to be motor fluctuations in patients with moderately advanced Parkinson's disease.

Selegiline as the primary treatment of Parkinson's disease--a long-term double-blind study

INTRODUCTION

To assess the therapeutic efficacy of selegiline combined with levodopa in the long-term treatment of Parkinson's disease (PD).

MATERIAL AND METHODS

A randomized, prospective, double-blind study on 44 patients with PD needing levodopa therapy after the initial double-blind treatment with placebo or selegiline was carried out. The patients were followed-up for 5 years under combination therapy.

RESULTS

Selegiline induced a significant (P < 0.001) slowing in the need to increase the daily levodopa dose in order to compensate for the progression of the disease. After 5 years of combination therapy the mean dose of levodopa was on average 320 mg lower in the selegiline group (405 +/- 59 mg vs 725 +/- 78 mg). The difference in the levodopa doses between the two groups increased along with follow-up time, as also the ratio of the levodopa doses (placebo/selegiline group). The number of daily levodopa doses needed to compensate for the occurrence of motor fluctuations was significantly lower in the selegiline group. The parkinsonian disability did not differ between the two groups because the clinical condition was kept as optimal as possible by adjusting the levodopa dosage. Nine patients in the placebo group needed initiation of additional dopaminergic therapy in comparison to one in the selegiline group (P = 0.004). During the 5-year follow-up period 11 patients were withdrawn from the selegiline group, 7 due to adverse events. There was no difference in mortality between the two groups.

CONCLUSIONS

Selegiline therapy offers beneficial long-term effets in the treatment of PD.