In pharmacokinetics, the rate of infusion (or dosing rate) refers not just to the rate at which a drug is administered, but the desired rate at which a drug should be administered to achieve a steady state of a fixed dose which has been demonstrated to be therapeutically effective.
Abbreviations include Kin, [1] K0, [2] or R0.
It can be calculated as the steady-state concentration in the plasma * the clearance.
Sample values and equations
| Variable | Abbreviation(s) | Example value | Formula |
| Dose (loading dose, or steady state/maintenance) | D (LD or MD) | 1000 mg | =Vd*C0 |
| Volume of distribution | Vd | 25 L | =D/C0 |
| Concentration (initial or steady-state) | C0 or Css | 40.0 mg/L | =D/Vd |
| Biological half-life | T½ | 14 hr | =0.7/Ke |
| Elimination rate constant | Ke | 0.05/hr | =0.7/(T½) =Cl/Vd |
| Elimination rate, or rate of infusion to balance elimination |
Kin | 50 mg/hr | =Css*Cl |
| Clearance | Cl | 1.25 L/hr | =Vd*Ke |
| Bioavailability | F | 1 | ![= \frac{[AUC]_{A}*dose_{B}}{[AUC]_{B}*dose_{A}}](http://wpcontent.answers.com/math/e/8/5/e85b84ef256dda4a748e1b7d86b8547e.png) |
Note that the "0.7" constant is a commonly used log approximation, but not the actual value. Another commonly used approximation is 0.693. -(ln(0.5)) = 0.69315.
References
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