Injection monitoring module

Injection monitoring module adapted and configured to be removably attached to a proximal extremity of an injection pen system for delivery of a drug, the injection pen system being equipped with a proximally located dose setting wheel and injection activator, the dose setting wheel being rotatable about a central longitudinal axis of the pen injection system for dose setting and during injection, wherein the injection monitoring module comprises:

• a hollow main body adapted and configured to be coaxially mounted on, and engage in co-rotation with, the dose setting wheel at the proximal extremity of the pen injection system;
• the hollow main body comprising a central longitudinal bore with a proximal extremity and a distal extremity;
• and
• an injection monitoring system located within the central longitudinal bore of the main body at the proximal extremity thereof and extending beyond said proximal extremity along said longitudinal axis in a proximal direction, said injection monitoring system includes a magnetic field producing means which is seated immovably within the bore of the hollow main body and a magnetic field sensor, located on the central longitudinal axis, wherein the magnetic field sensor is movable within the central longitudinal bore from a first monitoring position in which the injection monitoring system is not in abutting contact with a proximal surface of the injection activator, to a second monitoring position in which the injection monitoring system is in abutting contact with a proximal surface of the injection activator;
• and
• wherein the injection monitoring system further comprises a rotational movement measurement means, configured to detect and/or measure a user-induced rotational movement of the injection monitoring system, upon activation of the injection activator from the first monitoring position to the second monitoring position, and
• wherein the injection monitoring system further comprises a microcontroller configured to determine an injected dose in accordance with changes in magnetic field detected by the magnetic field sensor when said magnetic field sensor moves from the first monitoring position to the second monitoring position, and in accordance with any measurements made by the rotational movement measurement means.