In vitro measurement of therapeutic drugs in blood provides the physician indispensible information in determining proper therapy. The value of the information is compromised by the long time required by conventional measurement techniques. Biotrack proposes to develop a portable immunoassay system to quantitate concentrations of lidocaine, a cardiac-active drug, monitoring of which is crucial during therapy. The system will deliver objective, immediate results, patient-side, using an unmeasured drop of blood from a finger-stick as the sample. Chemistry developed in Phase I will be incorporated into a disposable reagent cartridge in dry (stable) form. Reaction between blood sample and reagents will be monitored by an instrument which has laser optics. Calibration will be achieved by reference to a standard method. Calibration data will be encoded on the reagent cartridge and read by the instrument. At the end of Phase II a working system will be available. Commercial application of the system in Phase III would take about a year for prototype development and clinical trials.