This may be followed by a sudden return of effectiveness, and the cycle can occur many times a day. This effect can be minimized by increasing the frequency of administered doses per day. Psychiatric disturbances can occur with the administration of levodopa-carbidopa including memory loss, anxiety, nervousness, agitation, restlessness, confusion, insomnia, nightmares, daytime somnolence, euphoria, malaise, and fatigue. Severe mental depression also has been reported, as well as suicidal tendencies, dementia, toxic delirium, hallucinations, paranoid delusion, psychosis, and hypomania. Orthostatic hypotension is a frequent adverse effect of levodopa therapy and occurs even with therapeutic dosages.
Tolerance usually develops within a few months.
Cardiac arrhythmias also can occur during levodopa-carbidopa therapy but are relatively infrequent. Flushing and hypertension have also been reported. Other adverse effects associated with levodopa-carbidopa include episodic hyperventilation, bizarre breathing patterns, hoarseness, and increased nasal secretions. Urinary retention, polyuria, and urinary incontinence also have been reported. Leukopenia, although infrequent, can occur during levodopa- carbidopa therapy and warrants temporary discontinuance of the drug.