Current pharmaceutical research directions tend to follow a systematic approach in the field of applied research and development. The concept of quality-by-design (QbD) has been the focus of the current progress of pharmaceutical sciences. It is based on, but not limited, to risk assessment, design of experiments and other computational methods and process analytical technology. These tools offer a well-organized methodology, both to identify and analyse the hazards that should be handled as critical, and are therefore applicable in the control strategy. Once implemented, the QbD approach will augment the comprehension of experts concerning the developed analytical technique or manufacturing process. The main activities are oriented towards the identification of the quality target product profiles, along with the critical quality attributes, the risk management of these and their analysis through in silico aided methods. This review aims to offer an overview of the current standpoints and general applications of QbD methods in pharmaceutical development.

Offering a systematic and multivariate analysis of the analytical procedure, development and validation of HPLC methods using Quality by Design approach are in the limelight of current research trends. A new, experimental design-aided HPLC method for fampridine was developed and preliminarily validated according to current in-force international guidelines for linearity, accuracy, robustness and precision.The method offers a high throughput sample analysis, with an elution time of 2.9 minutes, and signal detection without excipient interference performed at 262 nm. The method proved to be linear between 1–15 µg mL−1 (R2= 0.9996). The mean recovery was found to be 98.7 ± 1.9 % in the tested range of 2.5–7.5 µg mL−1. Low RSD values (< 1 %) were obtained for both model, intra- and inter-day precision. The limit of detection and limit of quantification were 0.24 and 0.78 µg mL−1, resp. The method proved to be applicable for active substance assay in a pharmaceutical dosage form.

Study of the effect of formulation variables on the characteristics of combination tablets containing enalapril maleate and indapamide as active substances using experimental designTo evaluate the influence of different variables on tablet formulations containing enalapril maleate and indapamide as active substances, two separate experimental designs were employed: one for evaluating powder properties and the other for tablet characteristics. Because of the low active pharmaceutical ingredient content, it was hypothesized that both powder and tablet properties could be determined only by the characteristics of excipients. In order to test this assumption, both experimental designs were done with placebo mixtures. The optimized formulation was then evaluated both with and without APIs. Results indicated that filler and lubricant percentage, along with compression force, were the most important variables during the formulation study. The optimized formulation showed similar characteristics in both cases for all responses, except for angle of repose and friability where only minor differences were observed. The combination of the applied approaches (using placebo composition and fractional experimental design) proved to be efficient, cost effective and time saving.Keywords: design of experiments, optimization, factorial design, placebo formulation Proper management of hypertension, one of the leading causes of cardiovascular disease, is of the utmost importance. It has been established that lowering of blood pressure can effectively reduce the risk of cardiovascular events and stroke, but finding the most appropriate therapy is often difficult (1). Combinational therapies employing an angiotensin-converting enzyme inhibitor (ACEi) and indapamide (IND) offer the advantage of using two highly effective agents, increasing both clinical efficiency and patient compliance (2-4). Low dose combinations of ACEis and diuretics have shown greater reduction in blood pressure and higher success rates in managing hypertension than either of the treatments alone (4-6). The most popular ACEis present in these combinations include perin- Szabo et al.: Study of the effect of formulation variables on the characteristics of combination tablets containing enalapril maleate and indapamide as active substances using experimental design, Acta Pharm. 66 (2016) 191-206.

A rapid and sensitive micellar electrokinetic capillary chromatography method with UV photodiodearray detection was developed for the simultaneous determination of atorvastatin and ezetimibe in fixed dose drug combination. Experimental conditions such as buffer concentration and pH, surfactant concentration, system temperature, applied voltage, injection parameters were optimized in order to improve the efficiency of the separation. The best results were obtained when using fused silica capillary (48 cm length X 50 µm ID) and 25 mM borate buffer electrolyte at pH 9.3 containing 25 mM SDS, + 30 kV applied voltage, 20 ºC system temperature. The separation was achieved in approximately 2 minutes, with a resolution of 7.02, the order of migration being atorvastatin followed by ezetimibe. The analytical performance of the method was verified with regard to linearity, precision, robustness and the limit of detection and quantification were calculated.