(from our old pal Wikipedia)
Toxicology
The LD50 of nicotine is 50 mg/kg for rats and 3 mg/kg for mice. 40–60 mg can be a lethal dosage for adult human beings. This makes it an extremely deadly poison. It is more toxic than many other alkaloids such as cocaine, which has a lethal dose of 1000 mg. The LD50 of cocaine when administered to mice is 95.1 mg/kg.
The amount of nicotine inhaled with tobacco smoke is a fraction of the amount contained in the tobacco leaves (most of the substance is destroyed by the heat). The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. For chewing tobacco, often called dip, snuff, or snus, which is held in the mouth between the lip and gum, the amount released into the body tends to be much greater than smoked tobacco.
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I'm no scientist here, but I wouldn't do it. I've heard of tobacco farmers dying because they touched a tobacco plant that had dew on it. I've also heard of inmates making a tea out of 2 packs of cigarettes to commit suicide with.
So, um... DON'T DO IT.