Strychnine is commonly used to kill small mammals and birds and is frequently a main ingredient in rat poison. It can also be deadly to humans in larger doses. It can be ingested, inhaled, or absorbed through the skin. First symptoms are painful muscle contractions, nausea, and vomiting. Muscle contractions eventually lead to asphyxiation. Death can result in as little as half an hour. It's a seriously unpleasant way to die, for human or rat.