Peeked the modafinil wikipedia and found this interesting quote:

"Monkeys will self-administer modafinil if they have previously been trained to self-administer cocaine.[28] As such, modafinil is classified by the United States FDA as a schedule IV controlled substance, a category for drugs with valid medical uses and low but significant addiction potential.[1][29]"

Never new it was a monkey that determined US drug policy, but I guess I'm not surprised!