If the half-life is short, then by the time you take another
dose (eg
oxycodone), virtually all of the previous
dose has been cleared, and in some people would have been entirely cleared. On the other hand, if the half-life is long (eg oxycontin, which slowly releases the drug into the body, rather than almost all at once like oxycodone),
then a substantial fraction of the active form of the drug may be in the system at the time of the next dose.