1. Vince Netto Universityof Pittsburgh:StudentPharmacist
Subcutaneous VS Intravenous Heparin: Interchangeable?
Route Peak Effect Duration of Effect Dosing Interval
Intravenous(IV) 5 – 15 minutes 2 – 6 hours BolusQ 4 – 6 hours OR
ContinuousInfusion(preferred)
Subcutaneous(SubQ) 2 – 4 hours 8 – 12 hours 5,000 – 20,000 unitsQ8 – 12 hours
Intravenousheparin, whengivenasboluses,isdosedevery4–6hours because itsanticoagulation
effectsonlylast2–6 hours postIV bolus; Thisdosinginterval providesuninterruptedanticoagulation.
Subcutaneousheparin isdosedevery8 – 12 hours because itsanticoagulation effectsonlylast8– 12
hoursaftersubcutaneous administration;Thisdosingintervalprovidesuninterruptedanticoagulation.
The graph above illustrates the bloodheparinconcentrations(andconsequently,bloodthinningeffects)
whenthe order“heparin5,000 unitsQ 12 hours” is givenIntravenously(BLUE) vsSubcutaneously(RED).
As illustrated,intravenousadministrationresultsinmuchhigheranticoagulation effectsthan
subcutaneousadministrationimmediately followingadose;However, IV heparin alsowearsoff more
quicklythansubcutaneousheparin,resultinginperiodsof interrupted therapeuticanticoagulation. This
correlatestoboth higherbleedrisk rightafterdosing,andhigherclotrisk before subsequentdosing.
(Graph depictsmodel estimatedbloodlevelsof heparinusingliterature derived PKparameters andis
intendedtoillustrate conceptsdiscussed. The model doesnotdepictactual PKstudydata.)
Summary
It isimportantto understandthatwhile sometimesthe same dosesof heparinare givenboth
intravenouslyandsubcutaneously,IV andsubcutaneousroutesare notinterchangeable. The regimens
differintherapeuticindication,degree of bloodthinning,anddosingfrequency. Thisisgeneralizable to
almostall medicationswith multiple routesof administration: Itisunsafe togive a medication by a route
otherthan that whichthe doctorhas ordered.
Higher peak
=
Higher bleed risk
Lower trough
=
Higher clot risk