Michael J. Fox

In a response to charges by conservative talk-show host Rush Limbaugh, Michael J. Fox defended his appearance in recent political campaign ads, saying he was neither acting nor off his medication for Parkinson's disease. On the contrary, he had been over medicated, the actor said during an interview aired on Thursday's "CBS Evening News with Katie Couric." "The irony of it is that I was too medicated," Fox told Couric, adding that his jumpy condition as he spoke to her reflected "a dearth of medication not by design. I just take it, and it kicks in when it kicks in." "That's funny the notion that you could calculate it for effect," he said. "Would that we could." The 7 1/2-minute interview with Fox, whose shaking at one point dislodged the microphone clipped to his jacket lapel, aired in two segments taped Thursday afternoon on the "Evening News" set. Fox drew some conservative criticism after an ad began running in Missouri during the World Series. It showed Fox visibly shaking while urging fans to vote yes for stem-cell research and Democratic Senate challenger Claire McCaskill and no to the Republican incumbent Jim Talent. "They say all politics is local, but it's not always the case," Fox says in the 30-second spot. "What you do in Missouri matters to millions of Americans Americans like me."