Molecular Dynamic Simulation Approach to Predict the Compatibility of Formulation Components of Salbutamol Sulfate Metered Dose Inhaler Free off Ethanol

Abstract

More than 50 years since the first introduction of metered dose inhaler (MDI) by Riker laboratories 1956. The major development in MDI manufacturing was the transformation from chloroflouro carbon (CFC) to hydroflouro alkane (HFA) which required a new engineering design to the MDI components and reformulation of existing MDI to fit the new propellant. Evolution of MDI formulation was challenging due to the low solubility profile of most excipients in HFA propellants and the limitation of generally recognized as safe (GRAS) excipients that could be delivered to the lung. The main purpose of this study was to develop a new salbutamol sulfate (SS) MDI using PEG400(1%) w/w as suitable alternative co-solvents to ethanol (10%)w/w. PVP-k30(0.001-0.0001%) w/w and Brij72(0.001-0.005-0.01%) were used separately as suggested stabilizer. In silico molecular dynamic (MD) simulation was carried out to investigate the compatibility of new excipients with SS and PEG400 before adding the HFA134a. Differential scanning calorimeter(DSC) was also run to evaluate the compatibility between formulations components that passed the visual observation test. Content per actuation was also used to estimate the developing formulation at accelerated stability conditions (40°C/75%RH).(N=10). MD simulation results demonstrated the compatibility of PVP-k30(0.0001%) w/w with other formulation's components before adding HFA134a propellant(small or negative value for and ). MD simulation results were also confirmed by DSC thermograms which indicate the compatibility between PVP-k30 based formulation due to a small change in endothermic maximum melting point compared with Brij 72 based formulation.Content per actuation of PVP-k30(0.0001%)w/w based formulation passed the accelerated stability test and there is a significant effect of stabilizer type and concentration on the emitted dose (p-value >0.05). This work confirms that MD simulations could save time and reduce the cost of experiments during the early stage of reformulation process of MDI.