the present invention relates to pharmaceutical formulations containing - 4 - amino - 1 --- pyrimidin - 2 - one - 2 &# 39 ;, 3 &# 39 ;- dideoxy , 3 &# 39 ;- thiacytidine , lamivudine , that are substantially free of ethanol and ethylenediamine - tetraacitic acid , and their use in medical therapy .