The half-life is the time in which half of a psychoactive substance is metabolized or excreted in the body. The half-life can therefore be used to describe how long the body needs until a psychoactive substance is metabolized or excreted. The half-life is therefore central to determining the dosing intervals.
An example: After the duration of a half-life, the substance is not completely degraded, but only half. This means that the remaining part (half) needs the same amount of time to be degraded or excreted - after two half-lives, a quarter of the original amount of substance remains in the body, after three half-lives an eighth. This continues until there is only one particle left, which in turn decays or is degraded.