Karo Parisyan, recently banned from the UFC, tested positive for large amounts of painkillers in a time period in which he would be fighting competitively. Anderson Silva admitted to taking painkillers prior to a landslide victory over Yushin Okami in UFC 134. What are the benefits of taking painkillers? Fighters can firstly take far more damage and pain than usual. Secondly, fighters can throw with more reckless abandon, having to worry less about leg checks and elbows.
This phenomena is not restricted to professional MMA. It pops up in boxing, kickboxing, and other forms of combat sports. Shockingly enough, this abuse pops up among youth in Karate and Taekwondo tournaments. At a young age, I was personally offered the standard 3-4 Advils, an unhealthy amount for a child, before fights at local Taekwondo tournaments. While I never took them, I witnessed other children smashing knees and elbows without so much as batting an eye while hopped up on painkillers. While not widespread, the use of painkillers among child athletes is common enough that it should be a cause for worry. This mixture of adrenaline and drugs can lead to some "mystery" and serious injuries that are only realized after the competition is over.