It is important that your doctor check your progress at regular visits. Tolcapone may have serious effects on your liver. You must have regular blood tests done to make sure this medicine is not affecting your liver.
Because tolcapone may have serious effects on your liver, you should watch for any signs of these effects. Signs include dark urine; itching; light-colored stools; loss of appetite; nausea (continuing); tenderness in upper right part of abdomen; unusual drowsiness, dullness, or feeling sluggish; unusual tiredness or weakness; or yellow eyes or skin. If you notice any of these signs, contact your doctor.
Do not stop taking tolcapone without first checking with your doctor. Your doctor may want you to gradually reduce the amount you are taking before stopping completely.
Tolcapone may cause dizziness or lightheadedness, drowsiness, weakness, or trouble in thinking or concentrating. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are not alert, well-coordinated, or able to think clearly.
Dizziness, lightheadedness, or fainting may occur, especially when you get up from a lying or sitting position. Getting up slowly may help. If you should have this problem, check with your doctor.
Hallucinations (seeing, hearing, or feeling things that are not there) may occur in some patients. This is more common in elderly patients.
You may experience nausea, especially when you first begin taking this medicine.
Tolcapone causes the urine to turn bright yellow. This is to be expected while you are taking it. This effect is harmless and will go away after you stop taking the medicine.