A sensitive and robust method for the determination of elution of the active drug substance, Sirolimus, in drug eluting coronary stents was developed using a USP Apparatus 4 elution system. The closed loop configuration of the elution apparatus and the low volume of elution eluent allows the low drug levels that elute from a single stent to be reproducibly monitored. The USP apparatus profile over 24 hours mirrors the 30 day in-vivo porcine profile, providing a in vitro release method that captures the entire release profile of the stent. The method discriminates between common purposely-made manufacturing and formulation defects.

The method employs a novel elution media containing an organic solvent component which permitted fitting the in-vivo elution curve to the in-vivo porcine profile. The method has been accepted by FDA as a release method for the elution of Sirolimus in cardiovascular stents.