{{Short description|Amount of drug given to keep previously established blood level}} {{Verification|date=February 2021}}{{Context||details=|date=February 2021}}
In pharmacokinetics, a '''maintenance dose''' is the maintenance rate [mg/h] of 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 [mg] of a drug is given at a regular dosing interval on a repetitive basis. Continuing the maintenance dose for about 4 to 5 half-lives (t<sub>1/2</sub>) of the drug will approximate the steady state level.<ref>{{cite book |last1= Houglum|first1= Joel |last2= Harrelson|first2= Gary |title= Principles of Pharmacology for Athletic Trainers|url= https://books.google.com/books?id=wbkoeZuwqjwC|access-date= 2012-01-26|year= 2010|publisher= SLACK Incorporated|isbn= 978-1-55642-901-9|page=51}}</ref> One or more doses higher than the maintenance dose can be given together at the beginning of therapy with a loading dose.<ref name="urlCp vs time - iv infusion with loading dose">{{cite web|url=http://www.chm.davidson.edu/erstevens/iv%20load%20Cp%20v%20t/iv%20load%20Cp%20v%20t.html |title=Cp vs time - iv infusion with loading dose |url-status=dead |archive-url=https://web.archive.org/web/20120216071112/http://www.chm.davidson.edu/erstevens/iv%20load%20Cp%20v%20t/iv%20load%20Cp%20v%20t.html |archive-date=2012-02-16 }}</ref>
A loading dose is most useful for drugs that are eliminated from the body relatively slowly. Such drugs require only a small maintenance dose to maintain the drug at the appropriate level in the body, but without an initial higher dose, reaching that level would take a long time.
== Calculating the maintenance dose ==
The required maintenance dose may be calculated as:
:<math>\mbox{MD} = \frac{C_p CL}{F }</math>
Where: :{| | ''MD'' || is the maintenance dose rate [mg/h] |- | ''C<sub>p</sub>'' || = desired peak concentration of drug [mg/L] |- | ''CL'' || = clearance of drug in body [L/h] |- | ''F'' || = bioavailability |}
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
==References== {{reflist}}
{{Pharmacology}}
Category:Pharmacokinetics