Systems, devices and methods to establish fluid communication between vessels. Containers and devices having a unitary multiple entry port structure and a port unitary cover with buttons or levers for the assembly of customized final dosages of injectable beneficial substances. Containers and devices having a protective port with a cover configured to hermetically seal second container(s) within the protective port. A vessel having at least two entry ports and at least one exit port, and at least one container containing a dosing regimen, the at least one container configured to be received by one of the at least two entry ports of the vessel, whereby upon connection of the at least one container to the one of the at least two entry ports of the vessel, the dosing regimen in the at least one container is transferred into the vessel. Modular dosing system for adding at least one amount of a medicament to a preparation in a modular construction. System for displaying a dosing regimen or single amount of a medicament, so that the administrator of the amount is able to precisely ascertain the amount administered to a patient.
