This potion is supposed to prevent Drowners from attacking Geralt but it did not work for me.
They attacked as per usual.

Just a quick question - do you mean during the waterhag fight, where you acquire the potion? Or did you try to use it at some other point in the game, and it didn't work? Just curious, really, since I felt once I had it I was strong enough to not really need it anymore...
Now, those annoying sirens, on the other hand...

Same thing happened with me, actually. I don't now why it does that.

Huh? As far as I know this potion is supposed only to mask Geralt's scent so waterhag will come back into her lair and into witcher striking distance, not to prevent drowners attacks. Geralt is even saying something like "...if she [WH] tolerates drowners presence, maybe hiding my own smell will be enough to catch her off guard..." Aard in the face when they are closing to you and they fall from the sky like a buckets of concrete. And when you have them grounded, they are just fodder for your silver sword. In fact, with a bit of training you can improve your timing to the point where buggers will be stunned by the fall for long enough to slaughter them with single and elegant coup de grâce.

I think you have three of these potions in your inventory so they are surely meant to be used throughout the game.
I tried it out on Drowners but not in this quest.

Thanks for the tips (later on you can also use the Hornwall horn to zap all sirens/erynias in the vicinity)... My complaint, however, wasn't so much that they are difficult to kill, just that there are so frigging many of them :-)
When you start clearing off question marks in Skellige they just pop up everywhere, so to me they are the vermin of TW3.
It very much reminded me of the drowner situation in TW1, where in the later acts the drowners are just one-hit-kills, but there's still hordes of them everywhere, so fighting them is an annoyance more than anything. You receive a ribbon there which is supposed to ward them off, but doesn't work properly. I always considered the Drowner Pheromones to be the TW3 equivalent of that, but apparently they copied the "not working properly" aspect as well ;-)

No, they are not. That quest is the only place they can be made, that is why you get three. The potion is not meant to circumvent drowner attacks across the entire game.

I see. I used only one potion for that entire quest.

For me, at least, those potions have worked on drowners elsewhere. I haven't tested it against every group of the things, but there were a couple of sewer-ish missions that were made less of a hassle by making them all ignore me.

Actually, I myself made the potion before I even started the quest. But it doesn't work for some reason.

What I meant was that you can't make it without this quest, and don't get a standard schematic for it. It is not a regular use potion. That would just be stupid, totally negating an entire enemy.

That is quite interesting, I did try to use it in Skellige on some groups of drowners (for research purposes mostly) but that didn't work, sometimes the "potion timer" didn't even pop up. It only working in sewer-like locations would make some amount of sense (since the scent could sort of be "washed away" be wind/rain etc). Will have to put that theory to the test...

As stated above, there was a similar mechanic in TW1, so it doesn't seem too far fetched to assume that this potion could work the same way...
Also, the game guide states there are two similar potions (for bears and nekkers), for some reason those apparently did not make it into the game. So, it may be that the intention was to make the pheromones usable outside of that particular quest, and CDPR just ended up not implementing it...