One of the most common symptoms of a nicotine overdose is vomiting, and so if you've taken it orally, you'll most likely puke it up and end up with pain & nausea instead. Even if pure nicotine
would be more lethal than cyanide, it isn't reliable.
A man survived an intake of 4 grams of pure nicotine and ended up surviving (although the circumstances are unclear). The same published paper also dismisses the LD50 estimate of 1mg/kg. Most cases I've read about are accidental poisonings in small dosages found in e-cigarettes, patches and gums, so I can't say for sure what the symptoms of a self-delivered 99% pure nicotine injection of 5+ grams would be (injection would be ideal). In the
2083 - A European Declaration of Independence manifesto, the author mentioned that he had purchased pure nicotine from China to be used as some sort of biological weapon. He described the shipping process as going smooth without a problem. I'm not sure if he ended up using nicotine as a poison or not.
Long story short:
* Pure nicotine is deadly and can easily be purchased.
* It's not a reliable method.
* Taken orally would most likely lead to a failed attempt.
* Symptoms from poisonings are extremely unpleasant (these were accidental poisonings, often in small dosages).
* I am not sure how fast death would be or what the symptoms of an injection of pure nicotine in a dose of 5+ grams via bloodstream injection would be, don't know if it'd be painful.
I'm still curious about the injection method. Excerpt from
Kobert's 1906 study:
After 1–4 mg of nicotine, these authors felt a burning sensation in the mouth, scratchy throat, increased saliva excretion, followed by a feeling of warmness emanating from the stomach, which spread over the chest and from the head to the toes and fingertips. Afterwards, the subjects became agitated, suffered from headache, dizziness, numbness, cloudy vision and hearing, light sensitivity, anxiety, dryness of the throat, coldness of the limbs, ructus [belch], flatulence, nausea, vomiting and rectal tenesmus. Respiration was accelerated and labored, pulse rate increased initially, and rose directly with the increasing dose; but later rose and fell erratically. After 45 min the experimenters lost consciousness. One of them suffered clonic seizures for 2 h, particularly of the respiratory muscles, also tremors of the limbs and shivering over the whole body. After the initial recovery, feelings of exhaustion, drowsiness and bleakness remained for 3 days.
I wouldn't recommend nicotine overdose as it's not a reliable, safe or peaceful method.
Adding to this, pure nicotine can be bought legally.
https://www.avvo.com/legal-answers/can-i-buy-pure-nicotine-legally--2661615.html