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.
A one-compartment open pharmacokinetic model describes the drug concentration-time course in the body post-administration. It views the body as a single, homogenous compartment without barriers to drug movement.
The term 'open' signifies unidirectional drug input and output processes.
Drugs dynamically traverse this compartment, assuming rapid equilibrium between plasma and other body fluids. Here, the rate of absorption exceeds that of elimination.
Elimination follows a first-order process with a consistent rate constant. Furthermore, plasma is the reference compartment, with plasma drug concentration change proportional to tissue drug concentration changes.
This model is ideal for predicting the pharmacokinetics of rapidly dispersing drugs, like intravenous bolus-administered theophylline, for safe and effective dosing.
The rate of drug presentation to the body is defined by an equation representing the difference between the rate of drug entry and exit.
The pharmacokinetic parameters can be calculated directly from the plasma concentration-time profile or by using non-compartmental methods.
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