1. A medical device (100) for administering drug therapy to a user over a long period of use, said medical device (100) comprising: a pumping mechanism (114) for administering a medication to the user； a first and second administration cannula to infuse said medicine transdermally to the user in a first and second infusion site； a controller (116) to control a first (108a) and a second (108b) mechanism to separately control the deployment of the first and second cannula to said user at the first and second infusion sites； The medical device (100) further comprises: a reusable portion (130) that houses the pumping mechanism (114), the controller (116), and the first and second mechanisms (108a, 108b) to control deployment, and a portion disposable (132) that houses a medicine container (106) and characterized in that a flow detection unit (120, 120a, 120b) is provided to detect if the first infusion site is no longer viable by detecting if the first cannula delivery is blocked or unable to deliver a desired flow of medication to the user, and because controller 116 is adapted to automatically retract the user's first administration cannula and automatically deploy the second administration cannula to the user, when the flow detection unit detects that the first infusion site is no longer viable.1. Un dispositivo médico (100) para administrar farmacoterapia a un usuario durante un periodo de utilización prolongado, dicho dispositivo médico (100) comprende: un mecanismo de bombeo (114) para administrar un medicamento al usuario； una primera y segunda cánula de administración para infundir dicho medicamento por vía transdérmica al usuario en un primer y segundo lugar de infusión； un controlador (116) para controlar un primer (108a) y un segundo (108b) mecanismo para controlar por separado el despliegue de la primera y la segunda cánula a dicho usuario en el primer y el segundo lugar de infusión； el dispositivo médico (100) comprende además: una porción reutilizable (130
