I am not sure of the mechanism of action of nitro tabs but I do know that there have been studies that have shown that nitrous oxides interacts with the opioid system which have shown low levels of addiction and withdrawal.
I am not sure whether nitro tabs are addictive or not, but you can develop a tolerance for nitroglycerin if you use it too often. That's why people who use nitroglycerin patches are supposed to wear them for 12 hours and then keep them off for the next 12 hours--excessive use will lead to physical dependence and your body will stop responding to the nitro as well. If you become physically dependent, you'll also experience withdrawal symptoms if you stop taking the drug. This isn't necessarily the same thing as addiction, though.
Click Here to search for a treatment center in your state that is right for you.