About ten days ago, the FDA Law Blog reported on the FDA’s order requiring manufacturers of 25 types of Class III “preamendments” devices to submit to the FDA information about those devices, including adverse safety and effectiveness data not already submitted to the Agency. The data is due by August 7, 2009, and is a first step toward putting those preamendments devices through the PMA process.

We have just two things to add — one explanatory and one predictive.

First, the explanation: The Medical Device Amendments to the Federal Food, Drug and Cosmetics Act were enacted on May 28, 1976, and generally required that manufacturers of the highest risk medical devices — Class III devices — obtain premarket approval from the FDA before marketing the devices. That requirement, however, would have forced companies to stop selling devices that were already on the market in May 1976. To avoid that result, the Medical Device Amendments permitted manufacturers to continue selling devices that were already being sold at that time — so-called “preamendments devices”– until the FDA either required a PMA for the device or took other action.

The FDA is beginning the process of completing the review of 25 of those preamendments devices.

Second, the prediction: The FDA is gathering data about certain preamendments devices. The Agency will presumably be looking closely at the safety and efficacy of those devices and then taking action with respect to them. That regulatory activity may affect whether manufacturers of the preamendment devices can assert a preemption defense.

If the FDA requires the preamendments devices to go through the PMA process, then PMA review plainly triggers preemption. See Riegel v. Medtronic, 522 U.S. __ (2008).

It’s possible, however, that the FDA will undertake some other degree of review, more intensive than mere 510(k) clearance, but not quite as rigorous as PMA approval. There isn’t much case authority discussing the availability of preemption on those facts, but defense counsel should be alert to the possibility.

Our crystal ball is always cloudy, but the fog here may be that of war: the dust from a new preemption battlefield that the future will bring.