Hi there!!
The problem of addiction in regards to nicotine is a little more complicated then you might think. Nicotine is as we know the addictive component of tobacco and other smoking/chewing products. Nicotine is a natural alkaloid stimulant produced by plants that belong to the nightshade family. These plants include tobacco, eggplants, tomatoes etc ( high concentrations are present in tobacco, with trace amounts in edible plants). makes its leaves poisonous to insects. Just as in other drugs nicotine is dangerous when it is overly used, however it’s overdose capability and toxicity is relatively low compared to other stimulants, although it is higher then that of alkaloids like nicotine. It is estimated that the LD50 of nicotine is .5-1.0 mg/kg in a human adult, which bring most likely estimate a lethal dosage to 30-60 mg. However nicotine poisoning is exceptionally rare and people have survived higher dosages.
Additionally nicotine is not the major problem substance in play in tobacco. In smoke for example there are some several thousand other carcinogenic and toxic substances like formaldehyde. Nicotine is not believed to be overtly carcinogenic.
So now to the question. People that wish to quit smoking would have to deal with the effects of possible nicotine withdrawal hence why nicotine patches were invented. In order to keep people off smoking or chewing which can bring into ya more dangerous chemicals, the patches are designed to only provide the substance that is principle in addiction to tobacco products. From there a patient can be weaned off of nicotine gradually. And before you ask... it is possible to overdose on nicotine patches, however patients usually receive patches during a course of smoking cessation. The patches only contain 15-21mg of nicotine that are gradually real eased thereby reducing risk of overdose or adverse effects:
