What is the half life of a drug mean?

A medication's biological or terminal half-life is how long it takes for half of the dose to be eliminated from the bloodstream. In medical terms, the half-life of a drug is the time it takes for the plasma concentration of a drug to reach half of its original concentration. ... We explain what half-life means for you.Mar 7, 2016 read more

A drug's half-life is the amount of time it takes for a drug to lose half of its strength in blood plasma. This is most easily measured in medications administered through an injection or IV drip. The half-life refers to the time it takes for half of a given dose to be eliminated from the body or bloodstream. read more

True, what works the first "half" and what in the 2nd "half". Its facinates me though, how often a medication, same drug family, different name, slight difference in the chemical make up, and the time spent in your body from one to the other is like apples to oranges. read more