Apparatus for the safe delivery of a beneficial agent to a patient

Apparatus for safe delivery of a beneficial agent to a patient comprising a chamber (98) for the agent through which a fluid passes to the patient and means for controlling the rate of delivery in two alternative modes. In the first mode fluid flow through the chamber is high enough to provide delivery of the agent at a rate independent of the actual fluid flow rate to provide a therapeutic dose of the agent in approximately thirty minutes. In the second mode, the fluid flow rate in the chamber is low enough for rate delivery of the agent to be at least partially dependent on fluid flow rate through the chamber. The control means ensures that a toxic concentration is not delivered to the patient nor develops in the patient's bloodstream. The control means may take various forms.