A system for injecting medicament into a patient via an injection pen having an injection pen housing and used with a removable needle assembly for each injection, the injection pen housing having a cartridge containing member for receiving a cartridge of medicament and threads on the exterior circumference of a distal end thereof that cooperate with grooves in the interior circumference of the needle assembly to facilitate their coupling and decoupling and replacement of a removable needle assembly each time the injection pen is used, characterized in that the system comprises: an adapter configured to be detachably coupled between an injection pen housing and a needle assembly and to deliver the medicament from the injection pen housing to the needle assembly, the adapter comprising grooves in the interior circumference of a proximal end thereof that are configured to be the same as the grooves of the needle assembly to cooperate with the threads on the injection pen housing to facilitate coupling and decoupling of the adapter and the injection pen housing, a cannula providing a drug throughway from the injection pen housing to a removable needle assembly, the cannula having a proximal portion that extends into the injection pen housing when the adapter is coupled to the injection pen housing for fluid path connection with the injection pen housing, and threads on the exterior circumference of its distal end that are configured to be the same as the threads on the injection pen housing to cooperate with the grooves in the interior circumference of a removable needle assembly to facilitate coupling and decoupling of the adapter and the needle assembly, the cannula having a distal portion that extends into the needle assembly when the adapter is coupled to the needle assembly for fluid path connection with the needle assembly; a sensor configured as a microchip provided in the adapter to sense the medicament and at least one characteristic about the medicament or its delivery to the patient and generate sensor data; and a device configured to wirelessly communicate with the sensor to obtain its sensor data. an adapter configured to be detachably coupled between an injection pen housing and a needle assembly and to deliver the medicament from the injection pen housing to the needle assembly, the adapter comprising grooves in the interior circumference of a proximal end thereof that are configured to be the same as the grooves of the needle assembly to cooperate with the threads on the injection pen housing to facilitate coupling and decoupling of the adapter and the injection pen housing, a cannula providing a drug throughway from the injection pen housing to a removable needle assembly, the cannula having a proximal portion that extends into the injection pen housing when the adapter is coupled to the injection pen housing for fluid path connection with the injection pen housing, and threads on the exterior circumference of its distal end that are configured to be the same as the threads on the injection pen housing to cooperate with the grooves in the interior circumference of a removable needle assembly to facilitate coupling and decoupling of the adapter and the needle assembly, the cannula having a distal portion that extends into the needle assembly when the adapter is coupled to the needle assembly for fluid path connection with the needle assembly; grooves in the interior circumference of a proximal end thereof that are configured to be the same as the grooves of the needle assembly to cooperate with the threads on the injection pen housing to facilitate coupling and decoupling of the adapter and the injection pen housing, a cannula providing a drug throughway from the injection pen housing to a removable needle assembly, the cannula having a proximal portion that extends into the injection pen housing when the adapter is coupled to the injection pen housing for fluid path connection with the injection pen housing, and threads on the exterior circumference of its distal end that are configured to be the same as the threads on the injection pen housing to cooperate with the grooves in the interior circumference of a removable needle assembly to facilitate coupling and decoupling of the adapter and the needle assembly, the cannula having a distal portion that extends into the needle assembly when the adapter is coupled to the needle assembly for fluid path connection with the needle assembly; a sensor configured as a microchip provided in the adapter to sense the medicament and at least one characteristic about the medicament or its delivery to the patient and generate sensor data; and a device configured to wirelessly communicate with the sensor to obtain its sensor data.