The actual mechanism is surprisingly similar to carbon monoxide. I forget the name of the molecule but it binds to hemoglobin with a higher priority then oxygen (exactly the same as carbon monoxide forms carboxyhemoglobin). I think any negative effects are due to the fact it acts upon all the organs unpredictably since its ingested whereas carbon monoxide acts on the brain very quickly because you're simply inhaling.
Sorry I can't give any specific deets.