A Novel Method for the Elution of Sirolimus (Rapamycin) in Drug-Eluting Stents

Abstract

A sensitive and robust method for the determination of the elution of an active drug substance, sirolimus, from drug-eluting c oronary stents was developed using a USP Apparatus 4 elution system. The closed-loop configuration of the elution apparatus and the small volume of eluent allow the low drug levels that elute from a single stent to be reproducibly monitored. The in vitro elution profile obtained from USP Apparatus 4 over 24 h mirrors the 30-day in vivo porcine profile, providing an in vitro release method that captures the entire in vivo release profile of the stent in a shorter time. This method discriminates between common manufacturing and formulation product defects that were intentionally made. The method employs a novel elution medium containing an organic solvent, which allowed the in vitro elution curve to be fit to the in vivo porcine profile. The method has been accepted by the FDA as a release method for the elution of sirolimus or rapamycin in cardiovascular stents.