The neurotoxin MPTP had been known earlier to cause PD-like symptoms (in humans and other primates, though not in rats) by interfering with complex I in the electron transport chain and killing dopaminergic neurons in the substantia nigra. However, further studies involving MPTP have failed to show development of Lewy bodies , a key component to PD pathology. Therefore, the mechanism behind MPTP as it relates to Parkinson's disease is not fully understood.  Because of these developments, rotenone was investigated as a possible Parkinson-causing agent. Both MPTP and rotenone are lipophilic and can cross the blood–brain barrier .
Many athletes, ball players, fighters, and any athlete who could benefit from the therapeutic relief often supplement with Deca Durabolin. Such individuals commonly have no desire to build any new lean muscle mass, but the relief alone is invaluable. Further, such relief can be obtained by a very low dose. A slightly higher dose will provide relief, greatly enhance overall recovery, and enhance muscular endurance. When it comes to performance enhancement, most athletes will find this steroid is hard to beat. More importantly, the relief effects of Deca Durabolin are not masking or false; this anabolic steroid shares nothing in common with over the counter painkillers or prescription painkillers like opiates. Such painkillers only mask the pain, whereas Deca Durabolin can actually heal the body.
Heavy consumption of the essential amino acid lysine (as indicated in the treatment of cold sores) has allegedly shown false positives in some and was cited by American shotputter C. J. Hunter as the reason for his positive test, though in 2004 he admitted to a federal grand jury that he had injected nandrolone.  A possible cause of incorrect urine test results is the presence of metabolites from other AAS, though modern urinalysis can usually determine the exact AAS used by analyzing the ratio of the two remaining nandrolone metabolites. As a result of the numerous overturned verdicts, the testing procedure was reviewed by UK Sport . On October 5, 2007, three-time Olympic gold medalist for track and field Marion Jones admitted to use of the drug, and was sentenced to six months in jail for lying to a federal grand jury in 2000.