Prediction of drug tissue to plasma concentration ratios using a measured volume of distribution in combination with lipophilicity.

One of the drug specific parameters needed in physiologically based pharmacokinetic (PBPK) models is the tissue to plasma drug concentration ratios (K(p) values). The aim of this study was to develop an empirical method for predicting K(p) values using a preclinically determined in vivo volume of distribution, in combination with descriptors for drug lipophilicity. Pharmacokinetic data in laboratory animals for a wide range of drug compounds were collected. Obtained correlations between K(p) values for muscle and other tissues, in a training set of 49 compounds, were used to predict K(p) values for a test set of 22 compounds, based on their volume of distribution and lipophilicity. Predicted K(p) values agreed well with experimentally determined values (n = 118), especially for noneliminating tissues (r(2) = 0.81) with 72% and 87% being within a factor +/-2 and +/-3, respectively. In conclusion, we present an empirical method based on a measured volume of distribution and a drug lipophilicity descriptor, which can be used to predict tissue K(p) values with reasonable accuracy.

Levodopa-carbidopa intestinal gel (LCIG) treatment in routine care of patients with advanced Parkinson's disease: An open-label prospective observational study of effectiveness, tolerability and healthcare costs.

BACKGROUND: Continuous infusion of levodopa-carbidopa intestinal gel (LCIG) can effectively manage motor and non-motor complications in advanced Parkinson's disease (PD). Healthcare costs, quality of life (QoL), effectiveness, and tolerability were assessed in routine care treatment with LCIG. METHODS: The seventy-seven patients enrolled in this prospective, open-label, 3-year study in routine medical care were LCIG-naïve (N = 37), or had previous LCIG treatment for <2 (N = 22), or ≥2 (N = 18) years. Healthcare costs were collected monthly. PD symptoms and QoL were assessed with the Unified Parkinson's Disease Rating Scale (UPDRS), 39-item Parkinson's Disease Questionnaire (PDQ-39), and EuroQoL 5-Dimension Visual Analog Scale (EQ-5D VAS); LCIG dose, safety, and tolerability were monitored. RESULTS: Mean monthly costs per patient (€8226 ± 5952) were similar across cohorts, remained steady during 3-year follow-up, and increased with PD severity and QoL impairment. In LCIG-naïve patients, significant improvements compared to baseline were observed on the UPDRS total score and PDQ-39 summary index score through 18 months (n = 24; UPDRS, p = 0.033; PDQ-39, p = 0.049). Symptom control was maintained during 3-year follow-up in LCIG-experienced cohorts. Small changes in mean daily LCIG dose were observed. Adverse events were common and generally related to the device, procedure, levodopa, or laboratory evaluations. CONCLUSIONS: Costs in LCIG-treated patients were stable over 3 years. LCIG treatment led to significant improvements in motor function and QoL over 18 months in LCIG-naïve patients and no worsening was observed in LCIG-experienced patients over 3 years despite natural PD progression over time. The long-term safety was consistent with the established LCIG profile.