nitrophenols and carbidopa--levodopa-drug-combination

Parkinson disease progression is associated with the development of levodopa short-duration responses and dyskinesias, as well as gait freezing. Levodopa dose adjustment and adjunctive treatment with dopamine agonists form the major therapeutic strategies. Catechol O-methyltransferase inhibitors are also appropriate considerations, whereas other drugs, including selegiline, amantadine, anticholinergic agents, and propranolol, have a more minor role.

Topics: Amantadine; Antiparkinson Agents; Benzophenones; Carbidopa; Catechol O-Methyltransferase Inhibitors; Catechols; Cholinergic Antagonists; Dopamine Agonists; Dose-Response Relationship, Drug; Drug Combinations; Dyskinesia, Drug-Induced; Enzyme Inhibitors; Humans; Levodopa; Nitriles; Nitrophenols; Parkinson Disease, Secondary; Propranolol; Randomized Controlled Trials as Topic; Selegiline; Tolcapone

The aims of the present study were to investigate the pharmacokinetic and pharmacodynamic (pk/pd) relationship of levodopa (l-dopa) in patients with advanced Parkinson disease (PD) and also to evaluate the effect of tolcapone on the pk/pd analysis of l-dopa in 1 patient with severe dyskinesias and fluctuations.. The pharmacokinetics (plasma concentrations of l-dopa and 3-O-methyldopa [3-OMD]) and motor effects (global score of the Unified Parkinson's Disease Rating Scale-III) of a single dose of l-dopa (plus the peripheral decarboxylase inhibitor 1:4) were determined in 14 patients with advanced PD. Patients were classified into 2 groups according to Hoehn and Yahr scale (stages 2 and 3). In 1 patient with severe dyskinesias and fluctuations, pk/pd of l-dopa were evaluated before and after coadministration of tolcapone at 100 mg 2 times daily for 1 month. The pk/pd analysis was based on an estimate of the maximal response model with a semiparametric approach to effect site equilibrium.. The highest levels of l-dopa and 3-OMD were observed in patients with stage 3 of Hoehn and Yahr scale. We showed differences in the pk/pd parameters after coadministration of tolcapone in 1 patient as well as the clinical improvement.Univariate analysis showed some significant correlations (P < 0.05) between l-dopa pk/pd parameters and patients' age, duration of l-dopa treatment, and duration of the disease. Multivariate analysis adjusted for patients' age, sex, duration of the disease, and Hoehn and Yahr stage showed that presence of diphasic (dyskinesia-improvement-dyskinesia [DID]) dyskinesias was the only independent predictor of larger threshold level - EC50 (mean concentration at half maximal effect) of l-dopa (P = 0.034).. The motor complications during long treatment therapy in patients with advanced PD especially with stage 3 Hoehn and Yahr scale were correlated to the higher plasma concentrations of l-dopa. In the presented study, patients with motor complications, especially with DID dyskinesias, exhibited a larger threshold level (EC50). The clinical improvement of a patient who received l-dopa and tolcapone can be explained by tolcapone-induced changes of peripheral and central l-dopa pharmacokinetics, which led to a decrease of l-dopa EC50 and 3-OMD concentrations. Our data indicate that pk/pd analysis may be helpful for monitoring the efficiency of therapeutic strategy applied in PD patients.

Topics: Age of Onset; Aged; Antiparkinson Agents; Aromatic Amino Acid Decarboxylase Inhibitors; Benserazide; Benzophenones; Carbidopa; Catechol O-Methyltransferase Inhibitors; Drug Combinations; Drug Therapy, Combination; Dyskinesias; Enzyme Inhibitors; Female; Half-Life; Humans; Levodopa; Male; Metabolic Clearance Rate; Middle Aged; Models, Biological; Nitrophenols; Parkinson Disease; Severity of Illness Index; Tolcapone; Tyrosine

This study investigated the feasibility, safety, and potential benefit in motor symptom control when switching from a dopamine agonist to tolcapone as an adjunctive therapy in patients with Parkinson's disease with a fluctuating response to levodopa (l-dopa). We determined the efficacy of 2 replacement strategies.. In this 10-week, randomized, open-label, stratified, parallel-group trial, 150 patients on a stable regimen of l-dopa/decarboxylase inhibitor in combination with bromocriptine, lisuride, or pergolide were switched to tolcapone. Primary end point was the change in daily "off" time from baseline to the end of week 10 as assessed by patient "on-off" diaries. Patients had their respective dopamine agonist reduced and finally withdrawn either by day 6 (short-term replacement, n = 72) or by day 23 (long-term replacement, n = 78).. At week 10, a significant reduction from baseline in daily "off" time (-15.9 +/- 19.3%; P < 0.001) and a significant increase of "on" time (14.6 +/- 19.8%; P < 0.001) were observed. Other efficacy variables (Unified Parkinson's Disease Rating Scale II, III, and IVb and Investigator's Global Assessment scores) improved significantly after switching to tolcapone. In general, there was no significant difference between the 2 replacement strategies. Treatment was better tolerated after the switch to tolcapone according to the IGA of tolerability.. Tolcapone, in principle, seems to be an alternative adjunct for patients, who fail to receive sufficient benefit from a dopamine agonist, for example, in case they do not tolerate an increase in dose or have unacceptable side effects. The switch from a dopamine agonist to tolcapone can be done safely within a few days.

Topics: Aged; Ambulatory Care Facilities; Aromatic Amino Acid Decarboxylase Inhibitors; Benserazide; Benzophenones; Carbidopa; Catechol O-Methyltransferase Inhibitors; Dopamine Agonists; Drug Combinations; Drug Therapy, Combination; Dyskinesias; Enzyme Inhibitors; Feasibility Studies; Female; Humans; Levodopa; Male; Middle Aged; Nitrophenols; Parkinson Disease; Severity of Illness Index; Time Factors; Tolcapone; Treatment Outcome

Tolcapone is a novel catechol-O-methyltransferase (COMT) inhibitor used as an adjunct to levodopa/carbidopa or levodopa/benserazide therapy to improve treatment of Parkinson's disease. The aim of the current study was to investigate the potential effect of tolcapone on the pharmacokinetics of carbidopa.. This was an open-label study in 12 parkinsonian patients receiving optimal levodopa/carbidopa therapy and tolcapone 200 mg three times daily for 6 weeks. Blood samples were taken at baseline (i.e. before the first tolcapone intake) and after 1-2 weeks and 6 weeks so that carbidopa pharmacokinetics before and during tolcapone treatment could be assessed.. No changes in any pharmacokinetic parameters of carbidopa were observed. The mean AUC(0,tau) and Cmax values at baseline were 0.39 microg ml-1 h and 0. 14 microg ml-1, respectively. During tolcapone treatment these values were on average 0.35 microg ml-1 h (AUC(0,tau), week 1-2), 0. 34 microg ml-1 h (AUC(0,tau), week 6 and 0.13 microg ml-1 (Cmax, weeks 1-2 and 6). tmax remained unchanged (approx. 2 h).. These results indicate that tolcapone does not affect carbidopa elimination and that no interaction of any clinical relevance occurs between tolcapone and carbidopa.

Topics: Aged; Antiparkinson Agents; Benzophenones; Carbidopa; Catechol O-Methyltransferase; Catechol O-Methyltransferase Inhibitors; Drug Combinations; Drug Interactions; Enzyme Inhibitors; Female; Humans; Levodopa; Male; Middle Aged; Nitrophenols; Parkinson Disease; Tolcapone

Two large, randomized, double-blind, placebo-controlled multicenter studies, one North American and one European, examined the efficacy and safety of 300 and 600 mg/day tolcapone in similar populations of patients (n = 379) with Parkinson's disease currently taking levodopa and experiencing motor fluctuations. Change in "on-off" function was the most important end-point assessment. The two studies found similar results. The percentage of "on" time improved significantly and "off" time was reduced. Daily levodopa dosage requirements decreased significantly. The most common and significant adverse event was increased dyskinesia; hallucinations were not frequently encountered.

Topics: Antiparkinson Agents; Benserazide; Benzophenones; Carbidopa; Catechol O-Methyltransferase Inhibitors; Dopamine Agents; Double-Blind Method; Drug Combinations; Drug Therapy, Combination; Enzyme Inhibitors; Europe; Humans; Levodopa; Nitrophenols; North America; Parkinson Disease; Randomized Controlled Trials as Topic; Tolcapone

Tolcapone (T) is a novel catechol-O-methyltransferase (COMT) inhibitor recently introduced for the treatment of Parkinson's disease. In clinical efficacy studies, T has been associated with a low incidence of diarrhea. The objectives of the study were to examine whether T and its adjunctive drug Sinemet (S) could influence intestinal fluid and electrolyte transport as a possible cause for the diarrhea. The studies were conducted in conscious dogs surgically prepared with Thiry-Vella loops constructed from a 40-cm jejunal segment. A physiologically buffered test solution was perfused into the orad stoma and collected from the caudad stoma. Secretions were collected at 15-min intervals and analyzed for volume, electrolytes, lipid phosphorus, and protein. The acute oral administration of T (10 and 30 mg/kg doses) was well tolerated. Concurrent acute administration of S (25 mg/kg) with T (30 mg/kg) was also well tolerated. The acute oral administration of T induced a dose-dependent efflux of intestinal fluid and electrolytes (sodium, potassium, chloride, and bicarbonate) secretion (P < 0.05). The oral coadministration of S (25 mg/kg) with T (30 mg/kg) accelerated the onset of the stimulation of intestinal secretion. Despite the significant stimulation of intestinal secretion, none of the dogs developed diarrhea, indicating the importance of intestinal compensatory mechanisms. Neither T nor T&S affected calcium, lipid, or protein efflux rates, suggesting that the stimulated secretion was not a consequence of intestinal mucosal injury. The chronic (seven-day) administration of T and T&S was associated with reduced intestinal secretory responses when compared with the acute administration of the same drugs; S enhanced the T-induced tolerance development. The basis for such tolerance is unknown. In conclusion, the stimulatory systemic actions of tolcapone on intestinal secretion may, under certain conditions, contribute to the induction of diarrhea in susceptible patients.

Topics: Animals; Benzophenones; Biological Transport; Carbidopa; Catechol O-Methyltransferase Inhibitors; Dogs; Dose-Response Relationship, Drug; Drug Combinations; Electrolytes; Enzyme Inhibitors; Female; Intestinal Mucosa; Intestinal Secretions; Intestines; Levodopa; Nitrophenols; Tolcapone