MAO-B and COMT Genetic Variations Associated With Levodopa Treatment Response in Patients With Parkinson's Disease.

The most commonly used Parkinson's disease (PD) treatment is the replacement of dopamine by its levodopa precursor (l-dopa). Monoamine oxidase-B (MAO-B) and catechol-o-methyl transferase (COMT) are enzymes involved in the metabolism and regulation of dopamine availability. In our study we investigated the possible relation among selected single-nucleotide polymorphisms (SNPs) in the MAO-B (rs1799836) and COMT (rs4680) genes and the therapeutic response to levodopa (l-dopa). A total of 162 Brazilian patients from the Pro-Parkinson service of Clinics Hospital of Pernambuco diagnosed with sporadic PD and treated with levodopa were enrolled. PD patients were stratified into 2 groups according to the daily levodopa dose. MAO-B and COMT SNP genotyping was conducted by polymerase chain reaction-restriction fragment length polymorphism. After multivariate analysis, we observed a significant difference between PD groups for the following variables: sex (P = .02), longer duration of disease (P = .02), longer levodopa therapy duration (P = .01), younger onset of PD (P = .01), and use of COMT inhibitor (P = .02). We observed that patients carrying MAO-B (rs1799836) A and AA genotypes and COMT (rs4680) LL genotype suffered more frequently from levodopa-induced-dyskinesia. In addition, we found an increased risk of 2.84-fold for male individuals carrying the MAO-B G allele to be treated with higher doses of levodopa (P = .04). We concluded that before beginning PD pharmacological treatment, it is important to consider the genetic variants of the MAO-B and COMT genes and the sex, reinforcing the evidence that sexual dimorphism in the genes related to dopamine metabolism might affect PD treatment.

Comparative bioavailability of 2 tablet formulations of levodopa/benserazide in healthy, fasting volunteers: a single-dose, randomized-sequence, open-label crossover study.

BACKGROUND: Currently, levodopa administered with decarboxylase inhibitors is the gold standard for the management of the motor symptoms of Parkinson's disease, a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta. In Argentina, only 1 commercial product is available with such composition; this study was contracted by the manufacturer to comply with new generic product regulations. OBJECTIVE: The aim of this study was to evaluate the fasting bioavailability of a new generic formulation of levodopa 200 mg/benserazide 50 mg tablets (test) and compare this generic formulation with the branded formulation (reference) to meet regulatory criteria for marketing the test product in Argentina. METHODS: A randomized-sequence, open-label, 2-period, crossover study was conducted between August and October 2009 in healthy Caucasian volunteers (n = 24; 18 males, aged 21 to 42 years, with a body mass index ranging from 19.7 to 26.0 kg/m(2)) in the fasted state. A single oral dose of the test or reference formulation was administered, and after a 7-day washout period, the other formulation was given. Blood samples were collected at baseline and at 10, 20, 30, 40, 50, 60, 70, 80, 90, and 105 minutes and 2, 2.5, 3, 3.5, 4, and 6 hours after dosing. Levodopa plasma concentrations were measured by high-performance liquid chromatography with electrochemical detection, without stereo-specificity assessment. The formulations were considered bioequivalent if the 90% CI of the geometric mean ratios (test/reference) for the C(max) and AUC(0-t) of levodopa were within the 0.8 to 1.25 range. Adverse events were monitored throughout the study, based on clinical parameters and patient reports. RESULTS: The geometric means (90% CI) of the C(max) for the test and reference formulations were 2462.02 (2312.06-3492.40) and 2542.85 (2394.49-3231.29) ng/mL, respectively; the AUC(0-t) was 3878.04 (3623.88-5393.09) and 3972.10 (3765.88-5393.02) ng/mL/h, respectively; and the AUC(0-∞)was 4610.37 (4315.71-6315.70) and 4728.96 (4502.17-6828.26) ng/mL/h, respectively. There were no significant differences in pharmacokinetic parameters between the 2 formulations. The test:reference ratios for C(max), AUC(0-t), and AUC(0-∞) were 96.82% (90% CI, 83.87-111.77), 97.63% (90% CI, 85.95-110.91), and 97.49% (90% CI, 84.09-113.02), respectively. No clinically significant adverse events were reported; this finding is probably the result of subjects not believing that their side effects were severe enough to be reported and not because of a genuine and absolute lack of predictable side effects. CONCLUSIONS: In this single-dose study, the test formulation of levodopa/benserazide tablets met the Argentinean criterion for bioequivalence to the reference formulation. (www.clinicaltrials.gov: NCT01327261).

Determination of memantine in human plasma by liquid chromatography-electrospray tandem mass spectrometry: application to a bioequivalence study.

A simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of memantine (I) in human plasma is presented. Sample preparation consisted of the addition of amantadine (II) as internal standard (IS), liquid-liquid extraction in basic conditions using a mixture of diethyl ether-chloroform (7:3, v/v) as extracting solvent, followed by centrifugation, solvent evaporation and sample reconstitution in methanol. Both I and II (internal standard) were analyzed using a C18 column and a mobile phase composed of methanol-water-formic acid (80:20:0.1, v/v/v). Eluted compounds were monitored using positive mode electrospray (ES) tandem mass spectrometry. The analyses were carried out by selected reaction monitoring (SRM) using the parent to daughter combinations of m/z 180>163 (memantine) and m/z 152>135 (amantadine). The peak areas from the analyte and IS were used for quantification of I. The achieved limit of quantification (LOQ) was 0.1 ng/mL; the assay exhibited a linear dynamic range of 0.1-50.0 ng/mL with a determination coefficient (r2) of at least 0.98. Validation results on linearity, specificity, accuracy, precision and stability, as well as on application to the analysis of samples taken up to 320 h after oral administration of 20mg (two 10mg capsules) of I in healthy volunteers demonstrated the applicability to bioequivalence studies.

[Levodopa for Parkinson's disease: What have we learned?]. / Levodopa en la enfermedad de Parkinson: Qué hemos aprendido?

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. Dopamine deficit is the cornerstone of its clinical manifestations. Levodopa, the main treatment for this condition, was first used for PD more than 40 years ago and today it still is the most powerful treatment for this disease. In recent years many advances have been made for understanding of the neurochemical mechanisms of this drug. Furthermore, new insights about the genesis of motor complications secondary to its use are known, specially related with the mode of its administration. This article updates the pharmacology of levodopa and its implications for the pathophysiology and treatment of PD. The new available presentations of levodopa are also reviewed. The implications of these advances for the treatment of this disease are commented.

Levodopa en la enfermedad de Parkinson: ¿Qué hemos aprendido? / Levodopa for Parkinson's disease: What have we learned?

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. Dopamine deficit is the cornerstone of its clinical manifestations. Levodopa, the main treatment for this condition, was first used for PD more than 40 years ago and today it still is the most powerful treatment for this disease. In recent years many advances have been made for understanding of the neurochemical mechanisms of this drug. Furthermore, new insights about the genesis of motor complications secondary to its use are known, specially related with the mode of its administration. This article updates the pharmacology of levodopa and its implications for the pathophysiology and treatment of PD. The new available presentations of levodopa are also reviewed. The implications of these advances for the treatment of this disease are commented.

[Pharmacokinetic comparison of Sinemet and Grifoparkin (levodopa/carbidopa 250/25 mg) in Parkinson s disease: a single dose study]. / Comparación farmacocinética de Sinemet y Grifoparkin (levodopa/carbidopa 250/25 mg) en pacientes con enfermedad de Parkinson avanzada: un estudio con dosis única.

BACKGROUND: There are doubts wether generic medications have the same bioavailability and efficacy compared with the original drugs developed by pharmaceutical companies with research capabilities. AIM: To compare the pharmacokinetics and clinical (motor) responses of Sinemet and Grifoparkin (generic carbidopa/levodopa 250/25 mg) in patients with advanced Parkinson's disease. PATIENTS AND METHODS: Patients were randomly assigned to Sinemet (15 patients 62 +/- 12 years old; mean disease duration 11 +/- 7 years) or Grifoparkin (15 patients, 64 +/- 11 years old; mean disease duration 12 +/- 4 years) groups. Medication and food were withheld 12 h before the study. Fifteen blood samples were collected (starting 9 AM) immediately before (sample 1, t = 0 min) and after (samples 2-15, t = 20-360 min) oral administration of a single dose of Sinemet or Grifoparkin, and plasmatic L-DOPA was quantified using HPLC with electrochemical detection. Additionally, each patient was clinically evaluated every 20 minutes, using the tapping test and the unified Parkinson's disease scale Hoehn & Yarh. RESULTS: Tmax (time at which the maximal L-DOPA concentration was reached) were 69 +/- 12 min and 64 +/- 11 min for Sinemet and Grifoparkin respectively (NS). Cmax (maximal L-DOPA concentration reached) was 3161 +/- 345 ng/ml for Sinemet and 3274 +/- 520 ng/ml for Grifoparkin (NS). The t1/2 (half life time), CL (clearance) and volume of distribution (Vd) values calculated were 159 +/- 32 min, 51.7 +/- 5.1 1/h and 3.6 +/- 1.2 l/kg for Sinemet and 161 +/- 48 min, 58.7 +/- 8 l/h and 3.0 +/- 0.7 l/kg for Grifoparkin (NS). UPDRS-III value for the best "on state" and for the worst "off state" were 23 +/- 11 and 50 +/- 19 for Sinemet and 20 +/- 7 and 46 +/- 13 for Grifoparkin respectively (NS). CONCLUSION: The results obtained showed that both drugs are bioequivalent in patients with advanced Parkinson's disease.

Comparación farmacocinética de Sinemet y Grifoparkin (levodopa/carbidopa 250/25 mg) en pacientes con enfermedad de Parkinson avanzada: un estudio con dosis única / Pharmacokinetic comparison of Sinemet and Grifoparkin (levodopa/carbidopa 250/25 mg) in Parkinson s disease: a single dose study

BACKGROUND: There are doubts wether generic medications have the same bioavailability and efficacy compared with the original drugs developed by pharmaceutical companies with research capabilities. AIM: To compare the pharmacokinetics and clinical (motor) responses of Sinemet and Grifoparkin (generic carbidopa/levodopa 250/25 mg) in patients with advanced Parkinson's disease. PATIENTS AND METHODS: Patients were randomly assigned to Sinemet (15 patients 62 +/- 12 years old; mean disease duration 11 +/- 7 years) or Grifoparkin (15 patients, 64 +/- 11 years old; mean disease duration 12 +/- 4 years) groups. Medication and food were withheld 12 h before the study. Fifteen blood samples were collected (starting 9 AM) immediately before (sample 1, t = 0 min) and after (samples 2-15, t = 20-360 min) oral administration of a single dose of Sinemet or Grifoparkin, and plasmatic L-DOPA was quantified using HPLC with electrochemical detection. Additionally, each patient was clinically evaluated every 20 minutes, using the tapping test and the unified Parkinson's disease scale Hoehn & Yarh. RESULTS: Tmax (time at which the maximal L-DOPA concentration was reached) were 69 +/- 12 min and 64 +/- 11 min for Sinemet and Grifoparkin respectively (NS). Cmax (maximal L-DOPA concentration reached) was 3161 +/- 345 ng/ml for Sinemet and 3274 +/- 520 ng/ml for Grifoparkin (NS). The t1/2 (half life time), CL (clearance) and volume of distribution (Vd) values calculated were 159 +/- 32 min, 51.7 +/- 5.1 1/h and 3.6 +/- 1.2 l/kg for Sinemet and 161 +/- 48 min, 58.7 +/- 8 l/h and 3.0 +/- 0.7 l/kg for Grifoparkin (NS). UPDRS-III value for the best on state and for the worst off state were 23 +/- 11 and 50 +/- 19 for Sinemet and 20 +/- 7 and 46 +/- 13 for Grifoparkin respectively (NS). CONCLUSION: The results obtained showed that both drugs are bioequivalent in patients with advanced Parkinson's disease.

Study of the biodistribution of the amantadine labelled with technetium-99m in Wistar female rats.

Amantadine (AMA) has been described as dopamine stimulant and norepineprhine release, capable to block the N-methyl-D aspartate (NMDA) glutamatergic and nicotinic receptors, enhancing the sexual behavior of the male rats and inducing hypersexuality in humans. The use of technetium-99m (99mTc) can be justified for its physical and chemical properties. The aim of this study was to label and evaluate the bioavailability of the AMA labelled with 99mTc (99mTc-AMA) in Wistar female rats. The solution of 99mTc-AMA was administered by intraperitoneal way and the animals were sacrificed in CO2 chamber 10 min after the administration of the radiotracer. Various organs were removed, weighted, their radioactivity was determined using an auto-gamma counter and the results were expressed as the percentage of the injected activity per gram of tissue (%ATI/g). In the control group only Na99mTcO4 was administered. The analysis of results shows that the highest uptakes 99mTc-AMA treated group were: ovary (7.11 +/- 1.43), spleen (3.54 +/- 1.05), thyroid (2.67 +/- 0.15), stomach (1.56 +/- 1.10), duodenum (0.87 +/- 0.52), muscular tissue (0.57 +/- 0.06), liver (0.52 +/- 0.25), and at control group: thyroid (16.45 +/- 2.57), ovary (1.28 +/- 0.12), liver (1.10 +/- 0.04), spleen (0.57 +/- 0.07) and muscular tissue (0.26 +/- 0.03). The results obtained suggest that 99mTc-AMA may be used to study the bioavailability of amantadine and evaluate its effect in sexual behavior in female rats.

[Microdialysis cerebral. Main application of this technique]. / Microdiálisis cerebral. Principales aplicaciones de la técnica.

INTRODUCTION: Microdialysis cerebral technique has been widely employed in order to study the neurotransmitter release. DEVELOPMENT: This technique present numerous advantages such as: allow to work with sample in vivo from animals freely moving, by means of microdialysis can be infused simultaneously different drugs in different points implanted probes in several coordinates; also allow carry out pharmacokinetics studies that show correlation with behavior patter as well as to study metabolic changes, which is not possible when this determination are carry out in tissue, in post mortem stadio. CONCLUSIONS: In the present work is carry out a review about the main results obtaining in the sensitization and abstinence to several drug study and approach to biochemical characteristics to Parkinson s disease (PD) by means of microdialysis technique. In relation to sensibilization studies, the temporal changes in different behavior pattern that modify after amphetamine administration have been studied. Microdialysis study allowed correlationate dopamine concentration with behavior pattern above mentioned. In relation with PD, dopamine concentration after systemic and central (intracerebral) administration of levodopa and another dopaminergic drugs have been studied in different nucleus of basal ganglia as well as its respectively behavior correlates.

[New dopaminergic agonists]. / Novos agonistas dopaminérgicos.

We present a brief review of the literature about dopaminergic agonists. We report the five known dopaminergic receptors, where they are located, the advantages and disadvantages of the employment in parkinsonian patients. The dopaminergic agonists were introduced to control the limitations of levodopa-increasing the therapeutic window. We analyse the pharmacocynetic efficacy and the side effects of cabergoline, ropinirole and pramipexole.

Novos agonistas dopaminérgicos / New dopaminergic agonists

Apresentamos breve revisão da literatura sobre os agonistas dopaminérgicos. Referimos os cinco receptores conhecidos e onde estão localizados, as vantagens e as desvantagens de sua utilização nos pacientes com a doença de Parkinson. Introduzidos com o objetivo principal de controlar as limitações da levodopa, aumentando a janela terapêutica, analisamos a farmacocinética, a eficácia e os efeitos colateria da cabergolina, do ropinirole e do pramipexole.

A clinical, pharmacologic, and polysomnographic study of sleep benefit in Parkinson's disease.

We assessed the effect of sleep benefit on motor performance in Parkinson's disease (PD) and analyzed its relation to pharmacologic and sleep measures. The sleep benefit phenomenon-motor improvement after sleep before drug intake-in patients with PD has been addressed by questionnaire studies, but objective data are scarce. Ten PD patients with sleep benefit were pairwisely matched to 10 PD patients without sleep benefit for gender, age, PD symptom duration, and medications. We examined motor performance at night before sleep, during morning baseline state immediately after spontaneous awakening, and continuously after intake of the usual levodopa dose. Plasma levodopa concentrations were measured serially and all-night polysomnography was performed. Between night and morning evaluations, motor state improved slightly in patients with sleep benefit and deteriorated slightly in patients without sleep benefit. The difference between both groups proved to be significant. After levodopa induced "on" state, patients with sleep benefit had more severe interdose "off" than those without. Levodopa concentrations and polysomnographic findings were similar in both conditions, although there was a trend toward more abnormal sleep measures in sleep benefit patients. Sleep benefit is a small but significant phenomenon. It does not clearly relate to a specific sleep variable; however, patients with sleep benefit showed a different response profile to levodopa. Subjective perception or possibly sensory mechanisms could play an additional role in sleep benefit in PD.