An effective method of construction of a linear estimator of AUC in the finite interval, optimal in the minimax sense, is developed and demonstrated for five PK models. The models may be given as an explicit C(t) relationship or defined by differential equations. For high variability and rich sampling the optimal method is only moderately advantageous over optimal trapezoid or standard numerical approaches (Gauss-Legendre or Clenshaw-Curtis quadratures). The difference between the optimal estimator and other methods becomes more pronounced with a decrease in sample size or decrease in the variability. The described estimation method may appear useful in development of limited-sampling strategies for AUC determination, as an alternative to the widely used regression-based approach. It is indicated that many alternative approaches are also possible.
Exposure to tobacco smoke is associated with a higher cardiovascular risk, especially in patients with coronary artery disease (CAD). The aim of the study was to evaluate the effect of active and passive tobacco smoking on the activity of endothelial markers in advanced atherosclerosis. We studied 181 consecutive patients with advanced CAD (53 women and 128 men) aged 60 ±8 years, including 102 active self‑declared smokers (56.3%). We determined plasma asymmetric dimethylarginine (ADMA), thrombomodulin (TM), and plasminogen activator inhibitor‑1 (PAI‑1) levels, along with serum cotinine concentrations as a marker of tobacco smoking. Plasma ADMA levels were higher in active smokers compared with nonsmokers (0.60 ±0.09 μmol/l vs. 0.49 ±0.08 μmol/l, P <0.001). There were similar intergroup differences in TM (4.60 ±2.11 ng/ml vs. 3.0 ±1.7 ng/ml, P <0.0001) and PAI‑1 levels (30.3 ±12.4 ng/ml vs. 23.6 ±11.3 ng/ml, P <0.0001). We observed positive correlations between cotinine and ADMA (r = 0.71, P <0.0001), TM (r = 0.53, P <0.0001), and PAI‑1 (r = 0.58, P <0.0001). In 21 patients (26.6%) who declared to be nonsmokers, cotinine levels (mean, 6.30 ±22.5 ng/ml) significantly correlated with ADMA, TM, and PAI‑1 (all P <0.001). A multivariate regression analysis showed that cotinine was an independent predictor of ADMA, TM, and PAI‑1 in the whole patient group. Despite long‑lasting endothelial injury in advanced CAD, continued cigarette smoking is able to further enhance endothelial damage by increasing ADMA levels and resultant inhibition of fibrinolysis.
Parkinson’s disease (PD) is a progressive, neurodegenerative disorder primarily affecting dopaminergic neuronal systems, with impaired motor function as a consequence. The most effective treatment for PD remains the administration of oral levodopa (LD). Long-term LD treatment is frequently associated with motor fluctuations and dyskinesias, which exert a serious impact on a patient’s quality of life. The aim of our study was to determine the pharmacokinetics of LD: used as monotherapy or in combination with ropinirole, in patients with advanced PD. Furthermore, an effect of ropinirole on the pharmacokinetics of 3-OMD (a major LD metabolite) was assessed. We also investigated the correlation between the pharmacokinetic parameters of LD and 3-OMD and the occurrence of motor complications. Twenty-seven patients with idiopathic PD participated in the study. Thirteen patients received both LD and ropinirole, and fourteen administered LD monotherapy. Among 27 patients, twelve experienced fluctuations and/or dyskinesias, whereas fifteen were free of motor complications. Inter- and intra-individual variation in the LD and 3-OMD concentrations were observed. There were no significant differences in the LD and 3-OMD concentrations between the patients treated with a combined therapy of LD and ropinirole, and LD monotherapy. There were no significant differences in the LD concentrations in patients with and without motor complications; however, plasma 3-OMD levels were significantly higher in patients with motor complications. A linear one-compartment pharmacokinetic model with the first-order absorption was adopted for LD and 3-OMD. Only mean exit (residence) time for 3-OMD was significantly shorter in patients treated with ropinirole. Lag time, V/F, CL/F and tmax of LD had significantly lower values in patients with motor complications. On the other hand, AUC were significantly higher in these patients, both for LD and 3-OMD. 3-OMD Cmax was significantly higher in patients with motor complications as well. Our results showed that ropinirole does not influence LD or 3-OMD concentrations. Higher 3-OMD levels play a role in inducing motor complications during long-term levodopa therapy.
24 January 2013 in Basic & Clinical Pharmacology & Toxicology