Growth and development can be investigated using readily observable demographic factors such as weight and age. Size is the primary covariate and can be referenced to a 70-kg person with allometry using a coefficient of 0.75 for clearance and 1 for volume. The use of these coefficients is supported by fractal geometric concepts and observations from diverse areas in biology. Fat free mass (FFM) might be expected to do better than total body weight when there are wide variations in fat affecting body composition. Clearance pathways develop in the fetus before birth. The use of postnatal age as a descriptor of maturation is unsatisfactory because birth may occur prematurely; therefore postmenstrual age is a superior predictor of elimination function. A sigmoid E(max) model (Hill equation) describes gradual maturation of clearance in early life leading to a mature adult clearance achieved at a later age.

中文翻译：

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基于机理的药代动力学大小和成熟度概念。

可以使用容易观察到的人口统计学因素（例如体重和年龄）来研究生长和发育。大小是主要的协变量，可以参考70公斤的异度体检者，其间隙系数为0.75，体积系数为1。分形几何概念和生物学各领域的观察结果支持了这些系数的使用。当影响人体成分的脂肪差异很大时，无脂肪物质（FFM）的效果可能会好于总体重。胎儿出生前会形成清除途径。使用出生后的年龄作为成熟的描述是不令人满意的，因为出生可能会过早发生。因此，月经后年龄是消除功能的良好预测指标。