Levofloxacin hemihydrates

Levofloxacin hemihydrate was prepared by the hydrolysis of its ethyl ester in aqueous EtOH in the presence of NaOH (06WOP2006/070275) and crystallization of anhydrous levofloxacin from EtOH and acetone containing 2 v/v% of water [06JAP(K)2006/273718],... 

A final experimental condition that has not yet received widespread consideration within the pharmaceutical sciences is the flow rate of the purge gas. A study by Kitaoka et al. (38) discusses marked differences in the melting behavior of dehydrated levofloxacin hemihydrate, depending on the experimental conditions used (described in more depth in the following section). These differences may be ascribed to a number of factors including the efficiency of removal of water of dehydration and differences in the thermal conductivity of the purged cell. Irrespective of the explanation, the choice of purge-gas flow rate (and indeed the gas itself) is an experimental parameter that needs to be considered. 

FIGURE 3.12 Effect of N2flow rate on the DSC curve of levofloxacin hemihydrate. (Reproduced from Kitaoka, H. et al., Chem. Pharm. Bull., 43, 649, 1995. With permission.)... 

Differential scanning calorimetry (DSC) curves of levofloxacin hemihydrate measured under various conditions showed different thermograms. This behavior was attributed to the dehydration process that resulted in a multiple-phase transition. Dehydration at higher temperatures (above 70° C) gave a sharp endothermic peak in the DSC thermogram due to the melting of the y-form, and at a lower temperature (50°C) it led to the observation of a sharp endothermic peak due to the... 

Levofloxacin (Levaquin, ()-(S)-9-fluoro-3-methyl-10-(4-methyl-l-piperazinyl)-7-oxo-2,3-dihydro-7H-pyrido[l,2,3-de]-l,4-benzoxazine-6-carboxylic Acid Hemihydrate)... 

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