Several readers recently asked if there is a good (free) site that lists the expiration dates of pharmaceutical patents. The Generic Pharmaceutical Association (GPhA) has a chart listing Upcoming Patent Expirations for 2007-09.  One fee-based service I know of is Drug Patent Watch

One can also do the reviewing themselves, of course, but determining if a patent has truly expired can be a tricky business full of pitfalls.  For those who want to get look into a patent’s status, there are a number of steps to perform.

First, if the patent application was filed after June 7, 1995, the expiration date is 20 years from the date it was filed. If the application was filed by June 7, 1995 and issued before June 8, 1978, the expiration date is 17 years from issuance. But, if the application was filed by June 7, 1995 and issued after June 7, 1978, the term is the later of 17 years from issuance or 20 years from filing.

However, keep in mind that a patent term may be extended for various reasons.  Some patents have had their terms extended based on extreme delays in government approvals outside the Patent Office. This is very unusual, and applies almost always to pharmaceuticals (for example, Claritin® or Prozac®), food products (Aspartame) or medical devices or procedures, where FDA approval can sometimes eat up most of the patent term before the drug can be brought to market.

For a list of patents with term extensions, see the Patent and Trademark Office’s Extended Term List.

Some patents have less than the normal life span because their terms are limited to the terms of earlier-issued patents through the use of a terminal disclaimer, which is a result of filing two applications which claimed essentially the same invention. Terminal disclaimers will be marked on the later-issued patent. Sometimes these are flagged by an asterisk after the patent issue date, but sometimes they only appear in the text of the patent or with the related application data on the face of the patent.

Even after issuance, there are various ways a patent can expire early. For example, if the maintenance fees are not paid, the patent expires at the end of the surcharge period (4.5, 8.5 or 12.5 years after issue). However, the caveat to this is that expired patents may be revived up to 24 months after they expire, so long as the failure to pay the fee was unintentional. If the expiration date was more than two years in the past, the patent cannot be revived.

You can use the USPTO’s Patent Application Information Retrieval (PAIR) system to determine if maintenance fees have been paid.

In addition, you must determine if there has been any reexamination or voluntary disclaimer which resulted in a loss of some or all of the claim scope. This should be noted on a certificate attached to the patent image on the USPTO database, usually as the last page in the image file.  It is possible that an issued patent can be withdrawn from issue on the order of the Commissioner of Patents.

Finally, you must also check to see if the patent been declared invalid by a court.  Unfortunately, this can also be a tedious task to search through court records.

If you are genuinely concerned about a particular patent, it may be advisable to have a patent attorney (for example, one of the attorneys here at Frost Brown Todd) do a validity study and opinion on the patent. The attorney can perform a search to find prior art which might invalidate the patent, and will review the patent’s file at the USPTO to see if there is anything which might affect the validity or scope of the patent.

If you know of other sources for expired patent information, drop me a line and I will provide updated information here.

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