Strange Side Effects Surprise Patients

But Nirenberg and other doctors say that many neurologists and general practitioners who prescribe these drugs are unaware of the severity of the side effects, so patients are often left in the dark.

"There is still not enough physician awareness of this," she says.

Strange Side Effects

More than 10 million prescriptions have been written for Mirapex since the drug was launched in 1997, according to Kate O'Connor, director of public relations for Boehringer Ingelheim Pharmaceuticals Inc., maker of Mirapex.

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Information about the possible behavioral side effects, including gambling, compulsive eating and increased sex drive, has been included with the product for the past several years. But O'Connor says that it is difficult to estimate how many people may have experienced these side effects.

"For the vast majority of people who take these medications, compulsive behaviors do not occur, although these isolated incidences are, of course, very unfortunate," she says.

Scientists have recently begun to quantify the behavioral changes associated with dopamine agonist drugs. In a study presented in late June at the International Congress of Parkinson's Disease and Movement Disorders conference in Chicago, more than 13 percent of 3,090 Parkinson's patients had a problem with compulsive gambling, buying, sex or binge-eating.

People who were taking either Mirapex or Requip had a two- to three-times greater chance of having one of the four impulse-control disorders.

"These disorders can often be devastating to people's personal lives, financial lives, and even physical health," says Dr. Daniel Weintraub, lead author of the study and assistant professor of psychiatry at the University of Pennsylvania School of Medicine.

Though Weintraub says that the benefits of the drug outweigh the negatives for most patients, he adds that "clinicians do have a responsibility to notify patients that these are potential side effects."

Nirenberg even says she fears that these side effects are more prevalent than the study indicates, because only four of the many types of irregular behaviors were analyzed.