About one in five patients taking a therapeutic dose of a dopamine agonist, a class of drugs used to treat patients with Parkinson's disease, may develop compulsive gambling or hypersexuality, according to a study of patients treated at the Mayo Clinic in Rochester, Minnesota.

By contrast, these behaviors were not seen in untreated patients, those taking less than a therapeutic dose of a dopamine agonist, or patients receiving treatment with carbidopa/levodopa alone.

"Physicians who care for patients taking these drugs should recognize the potential of the drugs to induce pathologic syndromes that sometimes masquerade as primary psychiatric disease," Dr. J. Michael Bostwick and co-authors caution in the current issue of the Mayo Clinic Proceedings.

Their study was designed to more accurately determine the prevalence of this treatment complication than previous studies have by limiting their study patients in the seven counties surrounding their clinic. Included were 267 patients treated between 2004 and 2006.

Sixty-six were taking a dopamine agonist, but only 38 were using doses in the therapeutic range (pramipexole 2 milligrams per day or more, or ropinirole 6 milligrams per day or more); 178 were taking carbidopa/levodopa without a dopamine agonist, and 23 were untreated.

Six men and one woman, ages 46 to 80, developed a compulsive syndrome, in some cases as early as 1 month after reaching the maintenance dose of the dopamine agonist. Five started pathologic gambling and five became hypersexual (both disorders developed in three of the patients). Other compulsive behaviors were noted as well.

The behaviors, which often went unabated for years, resolved after dose reduction or treatment discontinuation. Two patients received extended psychiatric care before the link to their Parkinson's disease treatment was noted.

The only patients who developed these syndromes were taking therapeutic dopamine agonist doses, for an occurrence rate in this group of 18.4 percent. Bostwick and associates suggest that this is still likely to be an underestimate because these problems may often not be reported or recognized.

"The problems can be life-changing events, with gambling depleting family finances or hypersexuality threatening marriage and reputation," the authors emphasize. "Physicians treating Parkinson's disease with dopamine agonists should obviously warn the patients, spouses, and families of such risks because they may not recognize the relationship to the drug until disastrous consequences have occurred."