Cyanide is highly acutely toxic. It is detoxified in the liver by first-pass metabolism
following oral exposure. As a consequence, exposure to a dose spread over
a longer period, through a day, for example, will result in lower toxicity, or higher
tolerance, than the same dose given in a single bolus dose. Exposure to high doses
can give rise to thyroid toxicity as a secondary effect of exposure due to the inhibition
of iodine uptake from the thiocyanate generated through the detoxifying action of
rhodanese. It is difficult to interpret human data in view of the difficulty in assessing
the actual absorbed dose in humans following acute fatal intoxication and the lack of
well-conducted studies on sublethal toxicity.