One-compartment open model

Fig. 39.4. (a) One-compartment open model with single-dose intravenous injection of a dose D. The transfer constant of elimination (excretion and metabolism) is kp - (b) Time course of the plasma concentration Cp and of the contents in the elimination pool Xp. 

Fig. 39.6. (a) Time courses of plasma concentration Cp in the one-compartment open model for intravenous injection, with different contingencies for the transfer constant of elimination kfe and the volume of distribution Vp. (b) Time courses of plasma concentration Cp as in panel (a) on semilogarithmic plots. 

One-compartment open model for continuous intravenous infusion... 

When infusion stops at time x, the plasma concentration Cp(x) decays exponentially according to the solution of the one-compartment open model in eq. 

In the case of a one-compartment open model with single-dose intravenous administration, the mean residence time is simply the inverse of the elimination transfer constant kp, since according to the above definition we obtain ... 

The mean residence time MRT can thus be defined as the time it takes for a single intravenous dose to be reduced to 36.8% in a one-compartment open model. This follows from the property derived above in eq. (39.105) and from eq. (39.5) ... 

In the special case of a one-compartment open model, it can easily be shown that the steady-state volume is identical to the plasma volume Vp which has been defined before in Section 39.1.1 (eq. (39.12)) ... 

The proper dose of ketoprofen for an optimized zero-order model to obtain the desired drug level pattern to remain in the therapeutic range for 12 h (twice-a-day formulation) was estimated from drug pharmacokinetic parameters [6] by conventional equations [3] on the basis of a one-compartment open model and was found to be 1 lOmg. 

Limited data are available on the GI absorption of amphetamine in humans. Beckett and Rowland3 reported serum concentrations of amphetamine in two healthy volunteers after a 15-mg oral dose of the D-isomer. Peak serum concentrations of 48 and 40 ng/ml were achieved at 1.25 h when the volunteers urine was acidified. Slightly higher serum concentrations were observed (52 and 47 ng/ml) if the urine pH conditions were not controlled. Rowland4 observed a peak blood concentration of 35 ng/ml, 2 h after a 10-mg oral dose of D-amphetamine to a healthy 66-kg adult. The half-life for the D-isomer was 11 to 13 h compared with a 39% longer half-life for the L-isomer. If the urine were acidified, excretion was enhanced and the half-lives of both isomers were reduced to approximately 7 h.5 Amphetamine demonstrates a linear one-compartment open model over the dose range 20 to 200 mg. 

The vaginal absorption of drug following its release from vaginal drug delivery devices may alternatively be described by a simplifled one-compartment open model with first-order drug absorption (Fig. 

One-Compartment Open Model In this simple model, the body is treated as a homogenous unit with an entry and an exit (i.e., open model) (Figure 2a). It is assumed that changes occurring in blood concentrations reflect similar changes in tissue levels as the xenobiotic rapidly equilibrates between blood and all the various tissues of the body. 

L. T. Lindstrom and D. S. Birkes, Estimation of popnlation pharmacokinetic parameters using destructively obtained data a simulation study of the one compartment open model. Drug Metab Rev 15 195-264 (1984). 

Tse and Szeto (1982) reported on the bioavailability of theophylline following single intravenous bolus and oral doses in beagle dogs (Table P3.1). Plasma theophylline concentrations after intravenous and oral administration were described by a one-compartment open model. The doses administered were as follows ... 

The general equations for a one-compartment open model operating under first order kinetics are ... 

The non-linear regression program supplied with the Hewlett-Packard 9845 minicomputer was used to solve the kinetic uptake phase equation for a one-compartment open model operating under first order kinetics ... 

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