Continuing the maintenance dose for about 4 to 5 half-lives (t1/2) of the drug will approximate the steady state level.
[2] A loading dose is most useful for drugs that are eliminated from the body relatively slowly.
Such drugs need only a low maintenance dose in order to keep the amount of the drug in the body at the appropriate level, but this also means that, without an initial higher dose, it would take a long time for the amount of the drug in the body to reach that level.
The required maintenance dose may be calculated as: Where: For an intravenously administered drug, the bioavailability F will equal 1, since the drug is directly introduced to the bloodstream.
If the patient requires an oral dose, bioavailability will be less than 1 (depending upon absorption, first pass metabolism etc.