I remember the Chuck Muncie issue of Sports Illustrated which discussed drug use in the NFL. Was this the first national story about drug use among pro athletes?
Now, of course, drug stories with athletes are common.
I remember that article shocked me just as much as the dogfighting story about Michael Vick. Of course, I was a kid when the SI article came out.
Congress investigate drug use among pro athletes starting in 1972. They recommended spotcheck urinalysis. The Players assoc. called it an “absolute outrage.” There were national stories, but they were short and sweet and short on names.
In 1974, Pete Rozelle fined 8 San Diego Chargers for drug use. The Players Union called it “McCarthyism at its best.” This was supposedly only for marijuana.
But the Muncie story was the blockbuster.
Jim Bouton described the widespread use of “greenies”, or amphetamines, among pro baseball players in Ball Four in 1970.
This OP makes me feel old. 
I can point to stories as early as the mid-fifties that railed against the widespread us of amphetamines in baseball. Ballplayers had started using them in the thirties, and “greenies” (as they were commonly known) were given to soldiers during WWII. As the health effects began to evidence themselves, the press gave the subject considerable coverage.
The first organized response to the issue of drugs in sports came in the late sixties, in the wake of the death of Tour de France cyclist Tom Simpson in 1967. Shortly after, the International Olympic Committee began an anti-doping campaign and began its testing program.
There were lots of articles in the 1970s about drug use in football, basketball, and especially baseball. Pitcher Jim Bouton wrote about it in his 1970 book “Ball Four,” and there was plenty of coverage of star players involved in drug-related arrests, such as Denny McLain ('72) and Orlando Cepeda ('75). I could go on and on, but I think I’ve made my point.
I wanted to touch on the story **samclem **referenced. The Chargers hired a shrink named Arnold Mandell in 1972 to work with their players. His approach? Give them all amphetamines to get pumped up for games and depressants to come down afterwards. Needless to say, this created a mess. In addition to the players suspended (Sam says 8, I recollect it was 11, but why quibble), Mandell was banned from football. Chargers tackle Walt Sweeney later sued the Chargers and the NFL, saying that the drugs that were improperly administered by his employer not only led to addiction but other long term health problems. He was awarded a $1.8 million judgment in 1997.