Comparison of two software programs to be used for the calculation of population pharmacokinetic parameters

Benchmarking therapeutic drug monitoring software: a review of available computer tools

Therapeutic drug monitoring (TDM) aims to optimize treatments by individualizing dosage regimens based on the measurement of blood concentrations. Dosage individualization to maintain concentrations within a target range requires pharmacokinetic and clinical capabilities. Bayesian calculations currently represent the gold standard TDM approach but require computation assistance. In recent decades computer programs have been developed to assist clinicians in this assignment. The aim of this survey was to assess and compare computer tools designed to support TDM clinical activities. The literature and the Internet were searched to identify software. All programs were tested on personal computers. Each program was scored against a standardized grid covering pharmacokinetic relevance, user friendliness, computing aspects, interfacing and storage. A weighting factor was applied to each criterion of the grid to account for its relative importance. To assess the robustness of the software, six representative clinical vignettes were processed through each of them. Altogether, 12 software tools were identified, tested and ranked, representing a comprehensive review of the available software. Numbers of drugs handled by the software vary widely (from two to 180), and eight programs offer users the possibility of adding new drug models based on population pharmacokinetic analyses. Bayesian computation to predict dosage adaptation from blood concentration (a posteriori adjustment) is performed by ten tools, while nine are also able to propose a priori dosage regimens, based only on individual patient covariates such as age, sex and bodyweight. Among those applying Bayesian calculation, MM-USC*PACK© uses the non-parametric approach. The top two programs emerging from this benchmark were MwPharm© and TCIWorks. Most other programs evaluated had good potential while being less sophisticated or less user friendly. Programs vary in complexity and might not fit all healthcare settings. Each software tool must therefore be regarded with respect to the individual needs of hospitals or clinicians. Programs should be easy and fast for routine activities, including for non-experienced users. Computer-assisted TDM is gaining growing interest and should further improve, especially in terms of information system interfacing, user friendliness, data storage capability and report generation.

Effect of apomorphine on cognitive performance and sensorimotor gating in humans

INTRODUCTION

Dysfunction of brain dopamine systems is involved in various neuropsychiatric disorders. Challenge studies with dopamine receptor agonists have been performed to assess dopamine receptor functioning, classically using the release of growth hormone (GH) from the hindbrain as primary outcome measure. The objective of the current study was to assess dopamine receptor functioning at the forebrain level.

METHODS

Fifteen healthy male volunteers received apomorphine sublingually (2 mg), subcutaneously (0.005 mg/kg), and placebo in a balanced, double-blind, cross-over design. Outcome measures were plasma GH levels, performance on an AX continuous performance test, and prepulse inhibition of the acoustic startle. The relation between central outcome measures and apomorphine levels observed in plasma and calculated in the brain was modeled using a two-compartmental pharmacokinetic-pharmacodynamic analysis.

RESULTS

After administration of apomorphine, plasma GH increased and performance on the AX continuous performance test deteriorated, particularly in participants with low baseline performance. Apomorphine disrupted prepulse inhibition (PPI) on high-intensity (85 dB) prepulse trials and improved PPI on low intensity (75 dB) prepulse trials, particularly in participants with low baseline PPI. High cognitive performance at baseline was associated with reduced baseline sensorimotor gating. Neurophysiological measures correlated best with calculated brain apomorphine levels after subcutaneous administration.

CONCLUSION

The apomorphine challenge test appears a useful tool to assess dopamine receptor functioning at the forebrain level. Modulation of the effect of apomorphine by baseline performance levels may be explained by an inverted U-shape relation between prefrontal dopamine functioning and cognitive performance, and mesolimbic dopamine functioning and sensorimotor gating. Future apomorphine challenge tests preferentially use multiple outcome measures, after subcutaneous administration of apomorphine.

Transdermal iontophoretic delivery of apomorphine in patients improved by surfactant formulation pretreatment

The objective of the present study is to evaluate the efficacy and the safety of transdermal iontophoretic delivery of R-apomorphine, a potent dopamine agonist, in combination with surfactant pretreatment in patients with advanced Parkinson's disease. Iontophoresis patches were applied in 16 patients for 3.5 h, with 0.5 h of passive delivery followed by 3 h of current application at a current density of 250 microA/cm2. Eight of these patients were treated with a surfactant formulation prior to iontophoresis. The pharmacokinetics, pharmacodynamic effects, systemic and local side effects of R-apomorphine were assessed. The plasma concentration vs. time profiles upon iontophoresis of R-apomorphine were described successfully by a novel pharmacokinetic model. The model suggests that only 1.9% of the dose that has been released from the patch accumulated in the skin. The patients treated with the surfactant formulations showed a statistically significant increase of bioavailability (from 10.6+/-0.8% to 13.2+/-1.4%) and of the steady state input rate (from 75.3+/-6.6 to 98.3+/-12.1 nmol/cm2 h) compared to the control patients (iontophoresis without absorption enhancers). In five out of eight patients in the study group and in three out of eight patients in the control group, clinical improvement was observed.