Injection monitoring module with magnetic rotation sensing

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

• a hollow main body adapted and configured to be coaxially mounted on, and engage in corotation with, the dose setting wheel at the proximal extremity of the injection pen system, the hollow main body comprising a central longitudinal bore having a proximal extremity and a distal extremity, and a central longitudinal axis;
• a magnetic field production means, located on or within the hollow main body, at the proximal extremity of the central longitudinal bore;
• an injection monitoring system comprising at least one or a plurality of magnetic sensors, the injection monitoring system being located at the proximal extremity of, and movable in translation along said central longitudinal axis within the bore of the hollow main body, 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;
• the injection monitoring module further comprising a rotational stop means configured and adapted to prevent rotational movement of the injection monitoring system about said central longitudinal axis during dose selection.