The Food and Drug Administration is warning that a stimulant used in treatments for the childhood condition attention deficit-hyperactivity disorder can trigger painful, long-lasting erections in rare cases.
The federal agency said Tuesday it is updating drug labels to include information about priapism, a condition that can permanently damage a patient's penis.
The stimulant, methylphenidate, is found in treatments including Ritalin, Concerta and Daytrana.
The agency said people should talk to their doctors before halting the drugs. Parents should talk to boys taking the drug so they are aware of warning signs. Medical help should be sought for patients on the stimulant who develop erections lasting longer than four hours.