I believe that a lifetime ban on sports people caught using drugs should be imposed. Athletes are well in tune with their bodies and should know what effect drugs have on them. Many athletes are role models for younger children and should remember that. Therefore, if they are caught using drugs and children see that they are banned permanently, that would help kids understand the seriousness of using drugs.
It depends on the extremity of the offence, someone who goes full out on steroids should see a long/lifetime bans but those who become subject to contamination of products should be given the chance to argue their case. Also those who take less serious drugs should be given shorter punishments, for example someone shouldn't get a lifetime ban for testing for cannabis because it has no positive effect on performance at all.
Drug penalties and laws are already too harsh as it is. Penalizing people for using them is silly when drug use should be a medical issue, not a political one. Everyone deserves a second chance and athletes who use drugs should be given a chance to change and redeem themselves.