Half-life of a drug

The speed in which a drug is metabolized in the liver to products easily eliminated in the urine and that have no therapeutic action, is what is called half-life, which is expressed in hours, the half-life is the time in which maximum concentration obtained with the dose of the drug has beenreduced a 50%. This parameter is useful to determine the dosing intervals of the medication. The half-life is also important to determine the time necessary to reach the steady state or equilibrium in plasma concentrations after starting a dosing regimen, to reach the steady state four to five half-lives are required. It also allows to determine the time necessary for the drug to be eliminated from the body after a multiple dose schedule. This levels it will determine if medication can be taken once a day, twice a day (every 12 hours) or three times a day (every 8 hours).

Dr. Juan Sabater-TobellaEuropean Specialist in Clinical Chemistry and Laboratory Medicine (EC4)Member of the Pharmacogenomics Research NetworkPresidente de EUGENOMIC®

Last modified: Nov 20, 2018 @ 5:26 pm