This invention relates to a macrolide composition. More particularly, this invention relates to a method of increasing the solubility of 3R, 4S, 5S, 6R, 7R, 9R, 11S, 12R, 13S, 14R-6-[(2S,3R,4S,6R)-4-dimethylamino-3-hydroxy-6-methyloxan-2-yl]oxy-14-ethyl-7,12,13-trihydroxy-4-[(2R,4R,5S,6S)-5-hydroxy-4-methoxy-4,6-dimethyloxan-2-yl]oxy-10-(2-methoxyethoxymethoxyimino)-3,5,7,9,11,13-hexamethyl-1-oxacyclotetradecan-2-one or roxithromycin. This invention further relates to a novel polymorph, (Form-III), of roxithromycin.
Roxithromycin, a 14-membered-ring, macrolide antibiotic, is very similar in composition, chemical structure (semi-synthetic) and mechanism of action to erythromycin. Roxithromycin is currently available in two forms, namely anhydrous and monohydrate form.
Roxithromycin exhibits activity against some sexually transmitted diseases, upper and lower respiratory tract infections, asthma, gum infections like gingivitis, and bacterial infections associated with stomach and intestinal ulcers. Roxithromycin is further regarded as the drug of choice for the treatment of opportunistic infections occurring in HIV/AIDS patients owing to its activity against Cryptosporidium spp., Mycobacterium avium complex, Pneumocystis carinii and Toxoplasma gondii. 
A disadvantage associated with roxithromycin is that it is a hydrophobic molecule because it has no free hydroxyl group and is thus poorly water-soluble and unstable in an acidic environment.
A further disadvantage associated with roxithromycin is that its poor water-solubility and instability in an acidic environment result in a decrease in the absorption and bioavailability thereof.
Yet another disadvantage of roxithromycin is that said decreased absorption and bioavailability require relatively large quantities of roxithromycin to be administered in order to achieve a therapeutic effect.
A disadvantage associated with the use of relative large quantities of roxithromycin is that there is a potential increase in the side-effects associated with this active ingredient.
An even further disadvantage associated with the use of relative large quantities of roxithromycin is that there is an increase in the production and manufacturing cost of roxithromycin dosage forms, thereby increasing the cost of treatment.