What are the effects of cyanide poisoning?

How is the poison entering your victim? Ingestion or inhalation or absorption? "Unconsciousness occurs within a few seconds of taking large doses of prussic acids or other cyanides, and death occurs within five minutes." -- "Poison and Poisoning -- a Compendium of Cases, Catastrophes & Crimes" by Celia Kellett, pg. 48

I can't find a LD50 for ingested cyanide for humans, but for various animals it seems to be around 0.5 to 1.5 mg/kg. So if we assume 1 mg/kg it'd take about 60 mg to kill her. You should probably use a little more to be certain. Whether it could be considered a quiet death... cyanide kind of suffocates you from the inside. The victim fells like she can't breathe. She might start to hyperventilate, she might become nauseous and vomit and start to seize, then she'll quickly lose consciousness and die. The whole process, like Rajah said, only takes a couple of minutes with a large enough dose. A pinkish-reddish discoloration of the skin is typical after death, like with carbon monoxide, and combined with the characteristic smell it might tip people off.

FYI - not everyone can smell prussic acid. If you can it is like bitter almonds, but some people can't smell it. (3 in 10, maybe, not sure - google.)

How exactly would you describe "bitter almond"? I know the scent of sweet almond, but I've read it's much different...

Can anyone survive from cyanide poisoning without taking any antidote?? I have to make a character survive from ingested cyanide (without going to hospital right away) and I'm searching how to do that.

I was wondering... is there any medication that he can take beforehand (for some kind of illness) so when he gets poisoned, that medication could fight the poisoning?? I don’t know much about poisons yet, I’m just wondering

We'll sometimes administer hydroxocobalamin to firefighters/victims of smoke inhalation. It generally works quite well. If the cyanide dose is large enough there's not much you can do, though, and I'm not sure how fast it is eliminated and if it would work when taken before the exposure to cyanide.

From memory, of working in a chemi lab where someone else was working with cyanide (it is useful in organic chemistry). The short answer is no.

The longer answer is that we were taught about two antidotes.

EDTA - which we didn't have because it was too expensive

Solutions A and B - which were solutions with Iron ions - cyanide forms a permanent bond with the Fe in the haemoglobin so you give it a different source of Iron. I do remember (vaguely) that the best form of Fe ion was one that is not that stable. (Possible Fe2+ - a while since I've done this). So the solution oxidises to Fe3+ which was not effective. So you had to mix the antidote on the spot, from two bottles, which I think were the Solutions A and B. However this is just a vague pointer for you to google the correct details.

Both of these were post-poisoning, not pre-poisoning.

I did skim a bit of Wikipedia http://en.wikipedia.org/wiki/Cyanide_poisoning but didn't read in detail (so the details missing from my account may actually be there). An important point was that the cure can be as bad as the poisoning - especially if issued to someone who has not been cyanide poisoned. So if you took a pre-emptive dose, you'd be poisoning yourself with the antidote.

Does it have to be cyanide? I am just thinking of the plots in various detective novels, where someone has built up a tolerance to arsenic and when given a dose that would normally kill, survive it because of the tolerance. I suspect there are other poisons you can build up a tolerance too.