Search results
Jun 20, 2023 · From this equation, one can quickly determine the half-life of a drug, given its predetermined rate constant k. An alternative half-life equation exists that relates half-life to other pharmacokinetic parameters known as the volume of distribution and clearance (Equation 3).
HALF LIFE. Half-life refers to the rate at which 50% of a drug is eliminated from the body. Half-life can vary significantly between drugs. Some drugs have a short half-life of only a few hours and must be given multiple times a day, whereas other drugs have half-lives exceeding 12 hours and can be given as a single dose every 24 hours.
The half-life of a drug is an estimate of the time it takes for the concentration or amount in the body of that drug to be reduced by exactly one-half (50%). The symbol for half-life is t½. For example, if 100mg of a drug with a half-life of 60 minutes is taken, the following is estimated: 60 minutes after administration, 50mg remains.
Pharmacokinetics, sometimes described as what the body does to a drug, refers to the movement of drug into, through, and out of the body—the time course of its absorption, bioavailability, distribution, metabolism, and excretion.
After 4 half-lives the amount of drug (6.25%) is considered to be negligible regarding its therapeutic effects. The half-life of a drug depends on its clearance and volume of distribution. The elimination half-life is considered to be independent of the amount of drug in the body.
Jul 30, 2023 · The half-life is the amount of time for serum drug concentrations to decrease by 50%. Defined by the equation t=(0.693xVd)/Clearance, a drug's half-life is directly proportional to the volume of distribution and inversely to clearance.
Half-lives are commonly used in pharmacokinetics to describe drug absorption and elimination. The elimination half-life also determines how quickly a drug accumulates. The elimination half-life is determined by clearance (CL) and the volume of distribution (V). A proportionality constant, ln(2), is needed to calculate the half-life. A useful ...
