Naltrexone significantly reduced the number of drinks per drinking day ( naltrexone : mean = 4.90 , SD = 2.28 ; placebo : mean = 5.90 , SD = 2.51 ) ( P = .009 ) and percentage of drinking days with estimated BAC 0.08 g/dL ( naltrexone : mean = 35.4 , SD = 28.40 ; placebo : mean = 45.7 , SD = 26.80 ) ( P = .042 ) .