ABSTRACT
The aim of the article was to study and model solvent effects on phytocompounds' extraction from Glycyrrhizae radix for substantiation of rational choice of the extractant in the technology of drugs obtained from this type of plant raw material. The process of extraction was carried out by simple maceration for 24 h at temperature 25°C ± 1°C and extractant/plant raw material ratio 5:1 (v/w). The content of hydro-ethanolic extracts based on ethanol solutions with concentration of 22, 41, 50, 71, 82, and 96% ± 1% v/v and some other solvents was studied by reversed phase high-performance liquid chromatography. The optimal range of solvent concentration for simultaneous extraction of chalcones and glycyrrhizic acid derivatives from Glycyrrhizae radix was determined. It was found that dielectric constant of the solvent plays a key role in the distribution process of phytocompounds between the phases; there is a certain range of dielectric constant values of the solvent-water solution, within which maximum phytocompound concentration in the extract can be observed; the dependency between phytocompound concentration in the extract and dielectric constant of the solvent-water solution can be described by equation lnC = a + b/ε+d/ε2.
ABSTRACT
BACKGROUND: The use of cost-effectiveness analysis for medical devices has proven to be challenging because of the existence of the learning effects in the device-operator interactions. The need for the relevant analytical framework for assessing the economic value of such technologies has been recognized. OBJECTIVES: To present a modified difference-in-differences (DID) cost-effectiveness methodology that facilitates visualization of a new health technology's learning curve. METHODS: Using the Premier Perspective database (Premier Inc., Charlotte, NC), we examined the impact of physicians adopting a bipolar sealer (BPS) to control blood loss in primary unilateral total knee arthroplasties on hospital lengths of stay and total hospitalization costs when compared with two control groups. In our DID approach, we substituted month-from-adoption for the calendar-month-of-adoption in both graphical representations and ordinary least-squares regression results to estimate the effect of the BPS. RESULTS: The results clearly demonstrated a learning curve associated with the adoption of the BPS technology. Although the reductions in length of stay were immediate, the first postadoption year costs increased by $1335 (extrahospital controls) to $1565 (within-hospital controls). Importantly, and also consistent with a learning curve hypothesis, these initial higher costs were offset by subsequent cost savings in the second and third years postadoption. CONCLUSIONS: The presented modified DID approach is a suitable and versatile analytical tool for economic evaluation of a slowly diffusing medical device or health technology. It provides a better understanding of the potential learning effects associated with relevant interventions.