First-order elimination rate constant K and half-life

5 First-order elimination rate constant K and half-life f1/2 

The first-order elimination rate constant K can be determined as shown in Eq. (1.4) and has units of 1/time. The larger the value of K, the more rapidly elimination occurs. Once K has been determined, then calculating the half-life t1/2 is straightforward (Eq. 1.5). 

Equations (1.4) and (1.5) were written intentionally in these two forms to indicate that Kand tll2 are functions of Cl and Vd, and not vice versa. The anatomy and physiology of the body, along with the physicochemical properties of the drug, combine to form the biopharmaceutical properties, such as Cl and Vd, which can be found in many reference books.25 

Clinically, the two pharmacokinetics parameters t1/2 and systemic clearance Cl are very important when determining patient-specific 

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