The safety of dopamine agonists in the treatment of Parkinson's disease

Pinostrobin mitigates neurodegeneration through an up-regulation of antioxidants and GDNF in a rat model of Parkinson's disease

Background: One of the most common neurodegenerative diseases is Parkinson's disease (PD); PD is characterized by a reduction of neurons containing dopamine in the substantia nigra (SN), which leads to a lack of dopamine (DA) in nigrostriatal pathways, resulting in motor function disorders. Oxidative stress is considered as one of the etiologies involved in dopaminergic neuronal loss. Thus, we aimed to investigate the neuroprotective effects of pinostrobin (PB), a bioflavonoid extracted from Boesenbergia rotunda with antioxidative activity in PD. Methods: Rats were treated with 40 mg/kg of PB for seven consecutive days before and after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD. After completing the experiment, the brains including SN and striatum were used for histological studies and biochemical assays. Results: PB treatment demonstrated a reduction of free radicals in the SN as indicated by significantly decreased MDA levels, whereas the antioxidative enzymes (SOD and GSH) were significantly increased. Furthermore, PB treatment significantly increased glial cell line-derived neurotrophic factor (GDNF) immunolabelling which has neurotrophic and neuroprotective effects on the survival of dopaminergic neurons. Furthermore, PB treatment was shown to protect CA1 and CA3 neurons in the hippocampus and dopaminergic neurons in the SN. DA levels in the SN were increased after PB treatment, leading to the improvement of motor function of PD rats. Conclusions: These results imply that PB prevents MPTP-induced neurotoxicity via its antioxidant activities and increases GDNF levels, which may contribute to the therapeutic strategy for PD.

The Human Experience with Intravenous Levodopa

Objective: To compile a comprehensive summary of published human experience with levodopa given intravenously, with a focus on information required by regulatory agencies.

Background: While safe intravenous (IV) use of levodopa has been documented for over 50 years, regulatory supervision for pharmaceuticals given by a route other than that approved by the U.S. Food and Drug Administration (FDA) has become increasingly cautious. If delivering a drug by an alternate route raises the risk of adverse events, an investigational new drug (IND) application is required, including a comprehensive review of toxicity data.

Methods: Over 200 articles referring to IV levodopa were examined for details of administration, pharmacokinetics, benefit, and side effects.

Results: We identified 142 original reports describing IVLD use in humans, beginning with psychiatric research in 1959–1960 before the development of peripheral decarboxylase inhibitors. At least 2760 subjects have received IV levodopa, and reported outcomes include parkinsonian signs, sleep variables, hormone levels, hemodynamics, CSF amino acid composition, regional cerebral blood flow, cognition, perception and complex behavior. Mean pharmacokinetic variables were summarized for 49 healthy subjects and 190 with Parkinson's disease. Side effects were those expected from clinical experience with oral levodopa and dopamine agonists. No articles reported deaths or induction of psychosis.

Conclusion: At least 2760 patients have received IV levodopa with a safety profile comparable to that seen with oral administration.

Safety overview of FDA-approved medications for the treatment of the motor symptoms of Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is among the most common of the neurodegenerative disorders. Treatment is primarily focused on correcting neurotransmitter imbalances. Several classes of medication are available for this purpose.

AREAS COVERED

A Medline search was performed to gather information about the safety of the medications approved for the treatment of the motor symptoms of PD. This was supplemented with additional articles obtained from online sources and information provided by the FDA and the manufacturers. The focus of this review is the side-effect and safety profiles of carbidopa/levodopa, dopamine agonists, selective monoamine oxidase inhibitors, catechol-o-methyltransferase inhibitors, anticholinergics and amantadine.

EXPERT OPINION

Though serious side-effects may occur, as a group, the medications used for the treatment of PD motor symptoms tend to produce side-effects that are mild to moderate in nature, and that primarily reflect the focus on dopaminergic therapies. Care plans for Parkinson's patients should be approached based on the needs of the individual as disease presentation, lifestyle, level of disability, concurrent disease states and the presence of non-motor symptoms make each case unique. Patients and caregivers must have realistic expectations about the use of PD medications.

The impact of extended release dopamine agonists on prescribing patterns for therapy of early Parkinson's disease: an observational study

Background

Dopamine agonists (DA) are the first-choice drug for treatment of the early stage of Parkinson’s disease (PD) in subjects younger than 70 years. Recently, a number of third generation DA have been marketed, including transdermal patch of rotigotine and extended release oral formulation of ropinirole and pramipexole.

We investigated the impact of third generation DA on management of the early stage of PD in an outpatient service for Movement Disorders in Italy.

Methods

Two 12-month observation periods were selected (January - December, 2007, and January - December, 2011) as representative for prescription of immediate and extended release formulations of DA respectively. Within each period, PD patients were divided into subgroups according to age (<65 years; 65–75 years; >75 years) or functional requirement (high; moderate; low). For each period, the number of subjects receiving monotherapy with DA, monotherapy with levodopa (LD), or combined DA/LD therapy and the relative doses were calculated. The severity of parkinsonian motor symptoms was calculated by means of the Unified Parkinson’s Disease Rating Scale part III (UPDRS-III) score. The frequency and severity of side-effects leading to discontinuation or reduction of DA drugs at each time point were also calculated.

Results

We found a significant reduction of daily LD dose (both as mono- and combined therapy) between the second and the first observation period. There was also a significant increase of monotherapy with DA and corresponding reduction of monotherapy with LD in patients aged 65–75 years, as well as in PD patients with moderate functional requirements. A significant reduction of frequency of side-effects was measured with extended release DA as compared to immediate release formulations. There were no significant differences of the UPDRS-III scores between the 2 observation periods in any subgroup.

Conclusions

Our results suggest that extended release DA might optimize therapeutic management of the early stages of PD even in patients older than 70 years of age.