I especially like the way the post tackles this important distinction:

We’ve often explained that the “learned intermediary doctrine” is just that — a doctrine, and not an affirmative defense. Plaintiffs bear the burden of proving causation as part of their case-in-chief. Plaintiffs must therefore prove that a different warning on a drug’s package insert would have changed the physician’s conduct and avoided an alleged injury. Because the learned intermediary doctrine is not an affirmative defense, defendants do not bear the burden of proof.

“Sophisticated users,” however, is described as a “defense,” not a doctrine. That may be appropriate because the defendant may bear the burden of proving that the user was sophisticated.

There is detailed discussion on this issue, and the post also looks at a question left unanswered by the decision. The post is well worth reading if you get anywhere near product liability cases.