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Elimination Rate Constant Formula:
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The Elimination Rate Constant (ke) represents the rate at which a drug is removed from the body. It is a fundamental pharmacokinetic parameter that describes the fractional rate of drug elimination per unit time.
The calculator uses the elimination rate constant formula:
Where:
Explanation: The elimination rate constant is calculated by dividing the volume of plasma cleared of the drug per unit time by the volume of distribution, which represents the apparent space in the body available to contain the drug.
Details: The elimination rate constant is crucial for determining drug half-life, calculating appropriate dosing regimens, and understanding how quickly a drug will be removed from the body. It helps in predicting drug concentration over time and optimizing therapeutic outcomes.
Tips: Enter the volume of plasma cleared in m³/s and volume of distribution in m³. Both values must be positive numbers greater than zero for accurate calculation.
Q1: What does the elimination rate constant tell us?
A: The elimination rate constant indicates how quickly a drug is removed from the body. A higher ke value means the drug is eliminated faster, while a lower value indicates slower elimination.
Q2: How is elimination rate constant related to half-life?
A: The elimination rate constant and half-life are inversely related through the formula: \( t_{1/2} = \frac{\ln(2)}{ke} \). A larger ke results in a shorter half-life.
Q3: What factors affect the elimination rate constant?
A: Factors include renal function, hepatic function, age, body composition, and specific drug properties. Disease states affecting kidney or liver function can significantly alter ke values.
Q4: Are there typical ranges for elimination rate constants?
A: ke values vary widely between drugs. Rapidly eliminated drugs may have ke values around 0.1-1.0 1/h, while slowly eliminated drugs may have values as low as 0.001 1/h.
Q5: Can elimination rate constant change over time?
A: Yes, ke can change due to factors such as enzyme induction/inhibition, changes in organ function, drug interactions, or the development of tolerance.