A maximum of 5 years can be restored to the patent. In all cases, the total patent life for the product with the patent extension cannot exceed 14 years from t

A maximum of 5 years can be restored to the patent. In all cases, the total patent life for the product with the patent extension cannot exceed 14 years from the product’s approval date, or in other words, 14 years of potential marketing time. I f the patent life of the product after approval has 14 or more years, the product would not be eligible for patent extension. all regulatory periods are divided into a testing phase and an agency approval phase. The regulatory review period that occurs after the patent to be extended was issued is eligible to be counted towards the following calculation: First, each phase of the regulatory review period is reduced by any time that the applicant did act not act with due diligence during that phase. The reduction in time would only occur after an FDA finding that the company did not act with due diligence. Second, after any such reduction, one-half of the time remaining in the testing phase would be added to the time remaining in the approval phase to comprise the total period eligible for extension. Third, all of the eligible period can be counted unless to do so would result in a total remaining patent term from the date of approval of a marketing application of more than fourteen years. An additional limitation on the period of extension is that the extension cannot exceed five years. For example, if an approved drug product which is eligible for the maximum of five years of extension had ten years of original patent term left at the end of its regulatory review period, then only four of the five years could be counted towards extension. The Patent Trademark Office is responsible for determining the period of extension. you can read more here - http://www.fda.gov/Drugs/DevelopmentApprovalProcess/SmallBusinessAssistance/ucm069959.htm http://www.fda.gov/Drugs/DevelopmentApprovalProcess/SmallBus...