This guidance represents the Food and Drug Administration's (FDA's) current thinking on this topic.It does not create or confer any rights for or on any person and does not operate to bind FDA orthe public. You can use an alternative approach if that approach satisfies the requirements of theapplicable statutes and regulations. If you want to discuss an alternative approach, contact the FDAstaff responsible for implementing this guidance. If you cannot identify the appropriate FDA staff,call the appropriate number listed on the title page of this guidance.