Crystalline form of cyano-1-cyclopropy1-7-1S,6S-2,8-diazabicyclo[4.3.0]nonan-8-yl)-6-fluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid

1. A pradofloxacin trihydrate of formula (II)

2. The pradofloxacin trihydrate of claim 1 , having an X-ray powder diffractogram having the reflections

2θ (2 theta)

10.6230

14.1386

18.4032

20.9422

22.5604

22.8420

24.5165

25.8426

26.4972

26.8759

27.1231

of high and average intensity (>30% relative intensity).

3. The pradofloxacin trihydrate of claim 1 , wherein the crystal system is monoclinic, the space group is P2 1 , the dimensions of the unit cell are a=12.4790(18) Å α=90°, b=12.1275(18) Å β=111.009(6)°, c=15.010(2) Å γ=90°, and the volume is 2120.6(5) Å 3 .