The MDMA study, which involved 21 patients and began four years ago, took years of planning. Although Mithoefer is affiliated with the University of South Carolina, the study was conducted at his private clinic and funded by a nonprofit group. After the DEA stalled approval for the research, he says, the university balked from sponsoring a study involving a controversial and otherwise illegal substance.
But MDMA is not the only drug that has spent time both on the street and in the laboratory.
MDMA, or methylenedioxymethamphetamine, has its roots in the medical community. It was developed and used surreptitiously by psychiatrists in the 1970s. If it was one day to return to the medicine chest, it would follow a long line of other drugs that remain illegal in one form but legal in another.
"If you look back over the history of many so-called 'street drugs,' many have origins in well-intentioned and scientifically sound theories for use in medicine and more noble purposes than just getting high," said Paul L. Doering, a pharmacology professor and director of the University of Florida's Drug Information and Pharmacy Resource Center.
"The distinction between illegal and legal is tenuous," he said. "The door swings in both directions. These drugs have to replace their tie-dye shirts with lab coats."
Though marijuana cigarettes are sold for medicinal purposes in some states, the drug remains technically illegal in federal law in all but one form.
Sold under the name Marinol, THC (the active ingredient in marijuana) is prescribed as an appetite stimulant to treat nausea in cancer patients receiving chemotherapy and weight loss in AIDS patients.
The popular and legal drug Adderall, which is given to children with attention-deficit disorder, is just one carbon molecule away from being the popular illegal drug methamphetamine.
Cocaine, a local anesthetic like Novocain, has the added benefit of restricting blood vessels to stop bleeding. It is regularly used in its liquid form in emergency rooms and in facial surgery.
The "date-rape" drug GHB is classified as a Schedule 1 drug and is illegal if possessed with the intention of drugging someone in a bar, but is classified as a Schedule 3 drug when prescribed as Xyrem for use in the treatment of narcolepsy.
Beyond just governmental bureaucracy, Doering and others say, other barriers remain in the way of conducting medical research on illegal drugs.
"There are several factors keeping these drugs out of the lab," he said. "The main challenge is overcoming their bad reputations and convincing the research community that under the right circumstances -- under evaluation and regulation -- these drugs can be tamed to help humankind."
In addition to government regulation and the drugs' bad reputations, an inability to patent and, therefore, make money off these substances also stall research.
Raw marijuana, literally a weed, cannot be patented and neither can a drug discovered decades ago like LSD.
Salvia divinorum, a hallucinogenic, is perhaps the newest plant to be recognized for both its recreational and potential medical uses.
Still legal in most states, the drug is under review by the DEA to determine whether it should be criminalized.
If it is declared illegal before scientists get a chance to begin research, some fear that the drug will face the same challenges of other illegal substances with medicinal potential.