Analog-computer method for rapid estimates of theophylline clearance using presteady-state plasma concentrations.
An analog-computer method is described that provides estimates of steady-state plasma theophylline concentration nd total body clearance well before steady-state is achieved. An analog computer was programmed to simulate single compartment disposition of plasma theophylline for a constant rate infusion and an initial bolus. The two simulations were algebraically summed and the curve displayed on an oscilloscope. A series of 20 simulations was performed to define the rate of theophylline administration as applied to the analog-computer rate constant. The method was then tested using patient data previously reported in the literature. Presteady-state plasma concentration-time data points (n = 72) for the 20 simulations were compared; r2 for the analog-computer fit with calculated values as 0.99995. Using data for four patients, the estimates of total body clearance compared favorably with values generated by nonlinear least-squares regression analysis. An r2 of 0.86 was obtained for the analog-computer fit to 16 presteady-state patient data points. Use of the analog-computer method may enable clinicians to adjust aminophylline doses early in therapy to achieve optimal plasma theophylline concentrations.
D003202:Computers, Analog; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D013806:Theophylline / Q000097:blood*
D013806:Theophylline