From the PDR:
The most common serious adverse reactions occurring with carbidopa-levodopa are choreiform, dystonic, and other involuntary movements. Other serious adverse reactions are mental changes including paranoid ideation and psychotic episodes, depression with or without development of suicidal tendencies, and dementia. Convulsions also have occurred; however, a causal relationship with carbidopa-levodopa has not been established.
Psychiatric: confusion, sleepiness, insomnia, nightmares, hallucinations, delusions, agitation, anxiety, euphoria.
Nice sides,eh?