A vial adaptor assembly, suitable for use with a vial containing a medicament and a syringe adaptor, which is in turn connectable to a syringe having a piston adapted for selectable displacement in a first direction for drawing fluid into the syringe and in a second direction for expelling fluid from the syringe, the vial adaptor assembly including: a vial connector for non-removable connection with the vial containing a medicament； a syringe adaptor connector for connection with the syringe adaptor； a pressure equalization chamber having a variable volume, which is sealed from the outside environment during use； a liquid pathway communicating between an interior of the vial containing the medicament and an interior of the syringe when the syringe adaptor is connected to the syringe adaptor connector and the syringe is connected to the syringe adaptor and the vial connector is connected to the vial containing the medicament； and a venting pathway communicating between the interior of the vial containing the medicament and an interior of the pressure equalization chamber, when the vial connector is connected to the vial containing the medicament, wherein the pressure equalization chamber and the venting pathway are mutually configured such that, when the syringe adaptor is connected to the syringe adaptor connector and the syringe is connected to the syringe adaptor and the vial connector is connected to the vial containing the medicament, substantially all of any of the medicament that becomes located within the pressure equalization chamber is removed therefrom via the venting pathway and returned to the interior of the vial by displacement of the piston of the syringe in the first direction.Ensemble adaptateur de flacon, approprié pour être utilisé avec un flacon contenant un médicament et un adaptateur de seringue, qui peut quant à lui être relié à une seringue ayant un piston conçu pour un déplacement sélectionnable dans une première direction pour aspirer un fl
