| Understanding Drug Half-Lives - by William Llewellyn
There are a number of factors that can affect the potency of a particular drug compound. One such factor, and perhaps one of the most important, is the half-life of the agent. In medicine, the term half-life refers to the duration it takes for half of a given drug dosage to break down in the body. It is not half of the total activity time, as this figure always refers to the time it takes to metabolize 50% of what is in still the body. For example, if we inject 100mg a steroid with a half-life of 4 hours, at the four-hour mark we should have only 50mg left as active. After another four hours have passed the drug is still in the body, however another half-life has expired and the total active dosage will be around 25mg. It may take several half-lives before the drug is completely inactive. |