Disclosed herein is a method for determining a dosing prescription for a medicament in a patient undergoing CRRT. The method generally includes administering to the bloodstream of the patient a fluorescent agent； administering to the patient at least one dose of the medicament； performing CRRT on the patient after administering the fluorescent agent to the patient； exposing the fluorescent agent to visible or infrared light； monitoring transcutaneously a change in the spectral energy from the fluorescent agent over a period of time； correlating a change in intensity of the spectral energy from the fluorescent agent to a clearance rate of the fluorescent agent from the bloodstream in the patient； calculating a clearance rate of the medicament in the patient； determining an amount of the medicament in the bloodstream of the patient as a function of time； and adjusting a dosing prescription of the medicament to the patient.
