The rate of augmentation over a period of 40 or 52 weeks was significantly lower with pregabalin than with pramipexole at a dose of 0.5 mg ( 2.1 % vs. 7.7 % , P = 0.001 ) but not at a dose of 0.25 mg ( 2.1 % vs. 5.3 % , P = 0.08 ) .