Propecia (finasteride) is a potent medication that works by stimulating hair growth in men diagnosed with male pattern loss. It's efficient for most cases of this disease but if it did not work for you during the first 12 months of the treatment it is unlikely to be efficient in the future. Do not stop taking Propecia without your doctor's recommendation as you can lose all the progress achieved. People who stop the treatment are likely to lose the hair that appeared as a result of taking Propecia within the next year. Being allergic to finasteride is a contraindication for taking this medicine.