Which brand or company propecia is more effective ?Merck ?

I suggest seeing an expert to evaluate your hair loss and consider the best treatment options. Non invasive options include PRP/progesterone or transplantation for improvement. Best, Dr. Emer

In general, manufacturing and sales of medications are highly regulated.  Just because a generic brand costs less does not mean it is less potent or less effective.

If you are getting the generic brand of finasteride the medication is by law supposed to be bio- equivalent which means you should get the same effect.  I have had patients with respect to other medications report differences among the generic brands in that they were less effective or had side effects.  It is easy to blame the type of medication for your hair change, but you should be aware that there are other factors involved.  Please consult your hair doctor.