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Exponential relationships half life

The hyperbolic relationship be tween plasma concentration and effect explains why the time course of the effect, unlike that of the plasma concentration, cannot be described in terms of a simple exponential function. A half-life can be given for the processes of drug absorption and elimination, hence for the change in plasma levels, but generally not for the onset or decline of the effect... [Pg.68]

Values for the data equation parameters can be obtained by the technique of curve peeling" that was illustrated in Figure 3.8. After plotting the data, the first step is to identify the terminal exponential phase of the curve, in this case termed the j3--phase, and then back-extrapolate this line to obtain the ordinate intercept (BO- It is easiest to calculate the value of by first calculating the half-life of this phase. The value for j3 then can be estimated from the relationship j3 = ln2/b/2 - The next step is to subtract the corresponding value on the back-extrapolated jS-phase line from each of the data point values obtained during the previous exponential phase. This generates the Q -line from which the a-slope and A intercept can be estimated. [Pg.34]

The plasma concentration versus time relationship in Equation (10.198) contains two exponential decay terms. The first exponential decay term contains the larger hybrid rate constant (/li), which dominates at early times during the distribution phase. Hence Xi is called the hybrid distribution rate constant. The second exponential decay term contains the smaller hybrid rate constant (/I2) which dominates at later times during the elimination phase. The slope of the terminal line is equal to —I2 rather than the negative value of the micro elimination rate constant (—kio), and hence I2 called the hybrid elimination rate constant. The relationships for the two-compartment elimination half-life are then written in terms of I2... [Pg.242]

The present model also allows calculation of the relationship between flow velocity at constant relative conversion and operating time in a fixed bed. In the past linear as well as exponential functions have been proposed for this property. In figure 8 the expected relationships according to the present model, linear decay and exponential decay are shown. The results of one representative experiment have also been shown. The present theory results in a decay curve which is between the linear and exponential relationships. The assumption of linear decay involves an underestimation of the activity half life the assumption of exponential decay, however, overestimates the half life of the initial flow velocity. [Pg.160]

The search for accelerated test methods (e.g., by increasing temperature or oxygen pressure) has yet to have sustained success. In many cases, an exponential relationship is found between half-life dose (detected using strain as the parameter) and dose rate that is suitable for inter- and extrapolations, see Figure 5.120 (Section 5.3.3.2). However, it should be noted that the relationship is not always that simple and any extrapolation on the basis of a few measurement points is extremely unreliable. [Pg.1477]

Effect of Load. It is also evident from the exponential character of the basic hfe-load relationships that, for any given speed, a change in load may have a substantial effect on the hfe. For a roller bearing, if the load is doubled, the hfe is reduced to one-tenth its former calculated duration. Similarly, if the load is halved, the hfe is increased tenfold. For a bah bearing, if the load is doubled, the hfe is reduced to one-eighth its former value. Likewise, if the load is reduced one-half, the life is increased eightfold. [Pg.532]


See other pages where Exponential relationships half life is mentioned: [Pg.179]    [Pg.294]    [Pg.312]    [Pg.85]    [Pg.315]    [Pg.85]    [Pg.146]   
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