In certain embodiments, a vial adaptor comprises a housing member, a connector configured to couple the adaptor with a vial, a regulator channel, and an extractor channel formed in the housing member. The extractor channel is configured to facilitate withdrawal of fluid from the vial when the adaptor is coupled to the vial. The regulator channel is configured to facilitate flow of a regulating fluid to compensate for changes in volume of a medical fluid in the vial. In some embodiments, an expansion member is disposed on the housing member and is configured to expand and contract in accordance with changes in the volume of a medical fluid in the vial.
