| abstract |
The invention provides crystalline minocycline base. In particular, three crystalline polymorphic forms, designated Form I, Form II and Form III, of minocycline base are provided. These are characterised by XRD and IR data. Processes for preparing the new polymorphic forms are also provided. For example, Form I is prepared by dissolving and/or suspending amorphous minocycline base in an organic solvent chosen from ethers followed by crystallisation from the mixture. |