Is Omnacortil Solution Right Medication For An Infant After Hypospadius Repair?

Hello doc, my 17 months old son was operated for Hypospadius repair surgery in Aug 2012, however he have not been able to urinate properly till now, and now his surgeon have prescribed Omnacortil Solution 5mg - 10 ml to be given twice a day for three weeks. i am wondering if the dose is too much, please help... thanks.