The four riders were said to have tested positive for Methylphenidate (which is also known as Ritalin) a stimulant.
In stage 17 of the 1982 Vuelta a España, while leading the race, Arroyo was tested positive for Methylphenidate, and got a 10 minutes time penalty.
Due to allegations that school officials coerced parents into administering psychotropic medication such as Ritalin to their child, an amendment to the IDEA was added called prohibition on mandatory medication.
A study in 2000 looked in detail at all 289 overdoses of MPH reported to the Children's Hospital of Michigan regional poison control center during 1993 and 1994 (excluded: 105 extended-release formulations or co-ingestants, to ensure MPH overdose effects were not confounded by other effects).