Yes, you can substitute the prescribed medication. Both products contain the exact same active generic ingredients: Imxia F 5% Topical Solution (Finasteride and minoxidil) and Hair4U F (Finasteride and minoxidil). Since the strengths and active components are identical, they will work the same way to treat your hair loss. However, I highly recommend informing your dermatologist before making the switch. This is just to ensure that any differences in inactive ingredients or the application mechanism (such as a spray versus a dropper) do not irritate your scalp. Rest assured, the therapeutic benefits of both formulations are equivalent.