Drug shortages are a conundrum for pharma. They're frustrating, even infuriating, to hospitals and patients. To counterfeiters, they're a promise of new business. For evidence, look no further than the ADHD drug Adderall.

Made by Teva Pharmaceutical Industries ($TEVA) and other generics companies, the short-acting form of Adderall has been in short supply since last year. The FDA says that's because of "active pharmaceutical ingredient supply issues." Adderall contains four amphetamine salts and is classified as a controlled substance.

Teva and other manufacturers blame those "issues" on the Drug Enforcement Administration's quota system, designed to limit supplies of controlled substances. The DEA has said that drugmakers are focusing on branded versions of Adderall rather than the cheaper generics, and that's the reason the generics are scarce.

Whatever the cause, counterfeiters have seized upon the opportunity. FDA warns that online sites are peddling fake Adderall. Instead of Adderall's real active ingredient, at least some contain painkillers, including the potentially habit-forming tramadol, The Wall Street Journal reports.

Adderall was added to FDA's official shortage list at the beginning of the year; parents have been struggling to source supplies of the drug for their children. As the WSJ reports, it was one of these patients who alerted Teva to the fakes, after noticing misspellings on the packaging.

Now, the FDA is investigating websites that are taking advantage of the ongoing Adderall hunt. "Rogue websites and distributors may especially target medicines in short supply for counterfeiting," FDA said in a statement. Perhaps a smart business decision for those rogues, but a big problem for everyone else.