7.3 : One-Compartment Open Model for IV Bolus Administration: General Considerations

The one-compartment model is a pharmacokinetic tool that models the body as a single, uniform compartment, facilitating the understanding of drug distribution and elimination. This model is particularly beneficial for intravenous (IV) bolus administration, where the drug rapidly circulates throughout the body.

The drug's presence in the body is defined by an equation representing the difference between the rates of drug entry and exit. Key parameters—elimination rate constant, half-life, apparent volume of distribution, and total systemic clearance—are calculated from the plasma concentration-time profile, steady-state concentration, and infusion rate.

The absorption rate constant is determined using the residuals method, which separates the plasma concentration-time curve into absorption and elimination phases. This method is ideal for quickly and completely absorbed drugs that follow one-compartment kinetics.

Furthermore, the model accounts for a lag time, the interval between drug administration and absorption onset. A bi-exponential equation can define the plasma concentration-time profile following IV bolus administration. In practical terms, this model assists in predicting the pharmacokinetics of rapidly dispersing drugs, like propofol administered via IV bolus. It provides vital information to ensure safe and effective dosing.