A definition section in the specification will almost certainly be taken as controlling, even, as here, where it contradicts the preferred embodiment. If used at all, extra care and attention should be taken to draft definitions only to the extent absolutely necessary.

Background / Facts: The patent being asserted here in response to a generic drug ANDA submission is directed to mixtures for preparing patients for colonoscopies. In particular, the patent discloses a combination of magnesium sulfate, potassium sulfate, and sodium sulfate, which can be digested in small volumes to safely and effectively induce colonic purging without causing “clinically significant electrolyte shifts.” In this regard, the specification expressly states that “[t]he terms ‘clinically significant’ as used herein are meant to convey alterations in blood chemistry that are outside the normal upper or lower limits of their normal range or other untoward effects.” If adopted literally, however, this definition would exclude the preferred embodiment, which caused alterations in some patients’ blood chemistry but those alterations were found to be “clinically insignificant.”

Issue(s): Whether the specification’s definition of “clinically significant” should be modified to include the preferred embodiment.

Holding(s): No. While acknowledging that “[a] claim construction that excludes the preferred embodiment ‘is rarely, if ever, correct and would require highly persuasive evidentiary support,’” the court found that a contradictory definition section satisfies this evidentiary burden. “Under our precedent, the patentee’s lexicography must govern the claim construction analysis. … Therefore, we disagree with the district court’s modification of the clear language found in the specification. We reverse the district court’s claim construction and construe ‘clinically significant electrolyte shifts’ to be ‘alterations in blood chemistry that are outside the normal upper or lower limits of their normal range or other untoward effects.’”

Full Opinion