40 days isn't enough time to gauge effectiveness, or lack there of. You really need to give it atleast 3 months.
Remember though, minoxidil is a hair stimulant (and a relatively mild one at that). It does nothing to disrupt the fundamental process of MPB. 5ar-inhibitors (fin/dut) attack hair loss from the DHT angle. Topical anti-androgens (such as spiro) do the same, although on a local level. It is best to include either fin or dut along with a topical anti-androgen as part of any hair loss regimen. Minoxidil is a good addition if the other two are already in place. Nizoral shampoo a few times per week cannot hurt things either, as its cheap and helps keep inflammation (another aspect of MPB) to a minimum.