Process for making spherical crystalline 5-hydroxytetracycline hydrochloride (oxytetracycline hydrochloride)

摘要

The invention relates to a new process for the preparation of easy-flowing (flowable) oxytetracyclin hydrochloride. According to the process of the invention, the crude, dry or filter-wet oxytetracyclin hydrochloride consisting of needle-shaped crystals is boiled with an organic solvent forming an azeotropic mixture with water, optionally a part of the solvent is distilled off in a form of an azeotropic mixture, then the mixture is cooled and the precipitated oxytetracyclin hydrochloride consisting of spherical crystals is separated and dried. Oxytetracyclin hydrochloride exists in two various crystal forms, the one of which is needle-shaped, while the other one consists of orthorhombic sheets. The crystals of this latter form are capable of forming spherical particles by coalescence. The crystal form consisting of spherical particles is much more useful for the pharmaceutical industry. By means of the new process easy-flowing (flowable) oxytetracyclin hydrochloride can be prepared in a favorable yield and with a high purity from the crude hydrochloride product consisting of needle-shaped crystals.