You will probably not be surprised that you are not the only Tysabri user who has asked for the box the vial came in. I have seen posts on other MBs where MS patients did exactly the same thing.
This method of tracking expiration dates is not a valid measure of how fast wholesalers and distributors in the aggregate are going through their inventory. But it is valid to make a rough calculation of how fast Biogen is going through each month's production. The more people from different parts of the country who report the dates an expiration date is seen, the more accurate the measure of the consumption rate at the manufacturer level.
Those end users who are patients can simply ask for the box if they are curious or want to share that information here. Others at the end user level include infusion center personnel or the physicians office if the infusion is being administered there. For example, a neurologist who posts on another board reported receiving a shipment of vials on 2/18, all of which were 11/05 expirations. That means the wholesaler who shipped them to the doc still had 08/04 production. It says nothing about Biogen's inventory.
Biogen manufactures Tysabri and sells it to Elan for U.S. sales. Elan sells it to wholesalers and distributors who, in turn, sell to sites administering the infusions. Since Biogen and Elan have to follow the FDA's GMP, I know they ship their oldest product first (first-in-first-out, or FIFO). I presume wholesalers and distributors do the same, as FIFO is standard operationg procedure with any dated product.
I have seen one post from a person who says he is a MS patient reporting a 12/05 vial on 1/31/05. If that post is accurate as a matter of fact (something I cannot validate), that means Biogen was all out of 08/04 production no later than 1/31/05. The more posts I see with 12/05 reports, the more comfortable I am about the validity of the underlying fact.
Since the "pipeline" between Biogen to the end user went from zero inventory before approval to whatever inventory is there now, the first couple of calculations will not carry a high confidence level. In a few months, however, with enough reports of expiration dates from end users, I will be able to report back how fast Biogen is going through each month's production. IMO, this information should be useful to MS patients considering going on Tysabri.
In any event, thanks for your response and help. I wish you well on Tysabri.