I've been doing some fascinating reading about the admissability of adverse event data in a pharmaceutical product liability case. "Post-sale" duty to warn concerns the marketing experience, and the related spontaneous adverse event reports, and accumulation and analysis of data.
The Third Restatement of Torts specifically addresses post-sale failure to warn duty, and states that the duty arises "when new information is brought to the attention of the seller." There's no affirmative duty to continue to test (forgetting for the moment any Phase IV commitments) but the manufacturer is supposed to keep abreast of scientific literature and related developments.
Now, the Federal Register specifically states that ADRs are not conclusive of causality (21 CFR 314.80(a)). In fact, a company "need not admit, and may deny" causality of an individual report (21 CFR 314.80(k)). The FDA has also stated that “[a]ccumulated [AE] cases may not be used to calculate incidences or estimates of drug risk" in a 1996 report. These tidbits have been used by defendants to exclude expert testimony on the incidence of ADRs, and actual ADR reports themselves, which is a shame for the plaintiffs, because they make such fun reading for a jury. There are exceptions, particularly in a Bendectin case which allowed expert testimony in 1985. ADR reports can be used to prove notice, however. A plaintiff could argue that the mere existence of reports indicates that a company had notice of possible issues, and a clever lawyer would refer to a large volume of reports, hoping a jury would assume that a big stack of 3500A reports meant that the drug had problems, even if they don't get to hear about the content.
Anyway, this is all leading to the Baycol litigation, where the defense for Bayer had evidence about "AER data" excluded from consideration. The decision cited the Federal Register, and those FDA reports warning against using ADR data inappropriately. A quote from an affidavit from Dr Janet Arrowsmith-Lowe, formerly with the FDA and CDC: "It is a well accepted pharmaco-epidemiologic principle that the biases affecting AERs preclude their use in calculating rates of events or in comparing rates of adverse events among pharmaceutical products." The court cited her affidavit several times, and accepted her arguments.
But what if a company chooses to use that type of data in their own defense (click link for "Spontaneous Adverse Event Reporting Information...)? If they make the case that post-marketing reports demonstrate the relative safety of their drug, will they later be able to make the claim to exclude such data in litigation?