How does double inclusion affect Markush groups in patent claims?

Double inclusion in Markush groups generally does not cause issues with claim indefiniteness. The MPEP 2173.05(o) provides specific guidance on this topic:

“The mere fact that a compound may be embraced by more than one member of a Markush group recited in the claim does not lead to any uncertainty as to the scope of that claim for either examination or infringement purposes.”

This means that if an element or compound in a claim falls under multiple categories within a Markush group, it doesn’t necessarily create ambiguity or indefiniteness in the claim. Patent examiners and drafters should consider this guidance when evaluating or constructing claims with Markush groups that might include overlapping elements.

To learn more:

• Markush groups
• double inclusion
• claim indefiniteness
• patent claims
• claim construction