Taking someone to purchase drugs

I have a Muslim worker who is addicted to mandrax. Daily after work he must smoke. Sometimes he works late and the place where he needs to buy the tablets (drugs) is not safe so he asks me to take him there so that he can go in and buy it and I must drop him home. If I don’t take him, he will walk down and it’s not safe. I have been doing that but it’s bothering my mind, am I not a party to the sin? What should I do? Even though by my not taking him he won’t stop.