Ok, nicotine patches or gums are not drugs. They are used to provide the nicotine to your system while you dissociate the fact of lighting up during your special activities.
Here is an example. When I'm on the airplane, i don't think of smoking. 12 hours pass by with no need to smoke at all. On the other side, when i try to read or study, i need a cigarette and a coffee. The reason for that being the fact that during college i got used to studying that way.
What I'm trying to explain here is the following:
There are 2 simultaneous addictions that we suffer
-Psychological addiction: It kicks in whenever u start to do something u have associated with smoking. Computer, reading, seeing someone light one up, cofee, beer.... That one usually kicks in stronger and sooner than the actual drug addiction, in a way that you might find yourself lighting up a fag, even when your blood nicotine levels are "confortable".
-Chemical addiction: If you manage to overcome the psych addiction, a couple days later, your body will show the symptoms of the detox. Thats the only serious part of quitting smoking. It actually can hurt, deprive you from sleeping or carrying a normal life (for some weeks). Now, knowing that lighting one up is the solution for that, is the mental trap that has been set for us (we have set for ourselves).
-So, what are patches and other nicotine supplements for? They are a way to maintain the comfortable levels of nicotine, while you figure out how to get rid of the habit. The treatment should not last longer than a month or two, and once u are comfortable doing your routinely things smoke-free, then, following the treatment, you lower the dose progressively, in order to make a smooth detox. More than stopping smoking, is a kind of... un-starting to smoke.
The drugs i mentioned above, are a completely different thing. Smokers have "educated" neuro-receptors to trigger realistic pleasure feelings by associating them with nicotine. We are animals after all. So these drugs are actual psychotropic agents which can block those feelings. Even if you smoke while on those drugs, they are supposed to take the pleasure off of the fact of smoking, making you realize that smoking is just breathing the residue of a stinky combustion.
So, secondary effects are almost obvious. As well as some drugs provide euphoria (most of them are illegal), this drug provides numbness to certain triggers. Therefor making it a prescription drug. I have read that the success rate of these drugs is actually very high, but knowing that it would affect my judgment, and capacity of thinking, i reckon they are a big no for pilots. At least for now.