VI. NON-CLINICAL STUDIES OF THE FINISHED DRUG ELUTING STENT (DES)

B. Engineering Evaluation

4. Corrosion Potential of a Drug Eluting Stent

If the underlying stent substrate of the drug eluting stent is metallic, FDA recommends that the sponsor evaluate the effects of cracked or delaminated coatings on corrosion resistance. We recommend that corrosion testing be performed after intentionally creating a defect in the coating, which xposes the base stent substrate. We recommend testing according to the methods described in ASTM F746 or an equivalent method. The sponsor can modify the method by incorporating the experimental setup described in ASTM F2129.

Additionally, since there is a reasonable expectation of stent overlap during clinical procedures, the potential for fretting corrosion between two drug eluting stents should also be addressed. The sponsor should ensure that micromotion between strut elements is actually occurring. We recommend that the sponsor incorporate examination of samples for fretting corrosion as part of fatigue/durability testing. A scientific rationale for the number of samples evaluated for fretting corrosion should be provided.

If a stent contains more than one type of metal, such as a laminate, we recommend that the resistance of the stent to galvanic corrosion be demonstrated. If stents of different materials will be overlapped during clinical procedures and the contacting or overlapping stents may be made of different materials, we recommend that the potential for galvanic corrosion between stents be addressed. We recommend testing according to the methods described in ASTM G71 or an equivalent method. Sponsors can modify the method by incorporating the experimental setup described in ASTM F2129.

A copy of the original document can by found on the FDA website, http://www.fda.gov.