Crystalline molecular complex of tadalafil and methylparaben

1. A crystalline molecular complex of tadalafil comprising tadalafil and a co-former selected from methylparaben.

2. A crystalline molecular complex of tadalafil according to claim 1 where the molar ratio of the co-former in the complex ranges from 1:3 to 3:1.

3. A crystalline molecular complex of tadalafil according to claim 2 where the molar ratio of the co-former in the complex is from 1:1.

4. A crystalline molecular complex of tadalafil and methylparaben of claim 1 , wherein the molecular complex is characterized by:

an X-ray powder diffractogram having peaks at 5.3, 11.6, 16.2, 20.4, 22.0, 24.2, and 28.2°2θ±0.2°2θ;

an infrared spectrum having peaks at 747, 1225, 1266, 1432, 1646, 1706, and 3343 cm −1 ±1 cm −1 ; or

both.

5. A crystalline molecular complex of tadalafil and methylparaben of claim 1 , wherein the molecular complex is characterized by at least one of the following:

an X-ray powder diffractogram pattern substantially in accordance with the pattern shown in FIG. 9 ; or

an FTIR spectrum substantially in accordance with the pattern shown in FIG. 10 .

6. A pharmaceutical composition comprising a crystalline molecular complex of tadalafil and methylparaben of claim 4 and a pharmaceutically acceptable carrier.

7. A pharmaceutical composition comprising a crystalline molecular complex of tadalafil of claim 1 and a pharmaceutically acceptable carrier.

8. A method for making a crystalline molecular complex of tadalafil and methylparaben of claim 1 , comprising the steps of:

grinding tadalafil and methylparaben; and

adding acetonitrile to the ground tadalafil and methylparaben.

9. A method for making a crystalline molecular complex of tadalafil and methylparaben of claim 1 , comprising the steps of:

slurrying tadalafil, methylparaben, and acetonitrile; and

drying the slurried tadalafil, methylparaben, and acetonitrile.