Each country should determine its own policy on drugs cheats. I personally favour life long banishment for any sportsman who takes a drug that will enhance his chance of beating his opponent(s). Any excuse along the lines of, "I didn't know the medicine contained, xxxx drug or had performance enhancing properties" is not acceptable. If an athlete needs medicine, then he or she should only use drugs cleared by the sport's national body. If none are immediately or obviously available, the athlete must seek advice from a doctor and if the medical decision is to take a banned or unknown substance, the athlete must register the prescription with the national body. It might lead to a short disbarment if the new drug is taken genuinely, under prescription for a medically recorded condition, while the sporting body tests its effects. This would not be a punishment, just an admin procedure.
Any other reason for taking a drug should cause a life long ban. The drugs don't just appear in the blood/urine by accident, the athlete deliberately ingests them while competing in an environment sensitive to dug abuse. No excuses, zero tolerance, a ban for life if caught.