In an interview with the Daily Mirror, Hathaway suggested that the two stars had to develop an intimacy in order to make the movie's love scenes seem authentic.
"We had to go to a lot of emotionally and physically vulnerable places and we spent a lot of time rehearsing," she said. "We watched a lot of love scenes that have been done throughout film history and talked about which ones we liked and which ones we didn't."
The actress added that she found it helpful to swap tales of past sexual experiences with her co-star.
She explained: "We talked about our own experiences with love and intimacy, about what turned us on and what didn't. So it was completely open from the get-go. Jake described it as a kind of intellectual orgy and I think that sums it up best."
Love & Other Drugs is now playing in US and UK cinemas.
