In
pharmacokinetics, a maintenance dose is the maintenance rate
g/hof drug administration equal to the rate of elimination at steady state. This is not to be confused with
dose regimen, which is a type of drug therapy in which the
dose gof a
drug is given at a regular dosing interval on a repetitive basis. Continuing the maintenance dose for about 4 to 5
half-lives
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...
(t
½) of the drug will approximate the
steady state
In systems theory, a system or a process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties ''p' ...
level.
One or more doses higher than the maintenance dose can be given together at the beginning of therapy with a
loading dose
In pharmacokinetics, a loading dose is an initial higher dose of a drug that may be given at the beginning of a course of treatment before dropping down to a lower maintenance dose.
A loading dose is most useful for drugs that are eliminated fro ...
.
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.
Calculating the maintenance dose
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.), requiring a larger loading dose.
See also
*
Therapeutic index
The therapeutic index (TI; also referred to as therapeutic ratio) is a quantitative measurement of the relative safety of a drug. It is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes ...
References
{{Pharmacology
Pharmacokinetics