1. A composition suitable for preventing recurrence of narrowing of the urethra in a patient after initial treatment by internal urethrotomy, expansion of the urethra, or urethral surgery, the use comprising the step of administering to the patient a pharmaceutically effective amount of a compound of the formula: wherein: R1 is an element of the group consisting of hydrogen, halogen, nitro, benzo, lower alkyl, phenyl and lower alkoxy； R2 is an element of the group consisting of hydroxy, acetoxy and lower alkoxy, and R3 is an element of the group consisting from hydrogen and lower alkenoxycarbonyl； wherein n is 1 or 2； and its pharmaceutically acceptable salts. 2. A composition according to claim 1, characterized in that it is halofuginone. 3. A composition according to claim 1, characterized in that it is administered to a patient by a route selected from the group consisting of an oral, parenteral and topical route. A composition according to claim 3, characterized in that it is administered to the patient by topical intraurethral application. A composition according to claim 4, characterized in that it is in a pharmaceutical carrier selected from the group consisting of gel, liquid, lotion, cream, ointment and spray. The composition according to claim 5, characterized in that it is administered to the patient until a warning of recurrence of urethral narrowing is achieved.1. Композиция, подходящая для предупреждения рецидива сужения уретры у пациента после исходного лечения путем внутренней уретротомии, расширения уретры или уретральной хирургии, причем применение включает стадию введения пациенту эффективного с точки зрения фармацевтики количества соединения формулы:в которой:R1 означает элемент группы, состоящей из водорода, галогена, нитро, бензо, низшего алкила, фенила и низшего алкокси；R2 означает элемент группы, состоящей из гидрокси, ацетокси и низшего алкокси, иR3 означает элемент группы, состоящей из водорода и низшего алкеноксикарбонила； причем n равно 1
