Study protocol for a randomised placebo-controlled trial of pramipexole in addition to mood stabilisers for patients with treatment resistant bipolar depression (the PAX-BD study) by Azim, L, Hindmarch, P, Browne, G, Chadwick, T, Clare, E, Courtney, P, Dixon, L, Duffelen, N, Fouweather, T, Geddes, JR, Goudie, N, Harvey, S, Helter, T, Holstein, E-M, Martin, G, Mawson, P, McCaffery, J, Morriss, R, Simon, J, Smith, D, Stokes, PRA, Walker, J, Weetman, C, Wolstenhulme, F, Young, AH, Watson, S, McAllister-Williams, RH