However , sustained attention , as measured by the Rapid Visual Information Processing ( RVP ) CANTAB test , showed a statistically significant interaction of fed versus fasting and post-dose time of testing ( F [ 1,28 ] = 6.88 , P = 0.01 ) , suggesting that 40mg oxymorphone ER after a high-fat meal versus fasting mitigates the learning effect in this particular cognition domain from 1 hour to 3 hours post-dose .