Last updated March 9, 2022, by Teresa Carvalho, MS
Fact-checked by Ana de Barros, PhD
The therapy usually is prescribed to people who are already taking carbidopa and levodopa but whose symptoms have failed to respond to those therapies.
How Tasmar works
Parkinson’s disease is characterized by the progressive degeneration and death of nerve cells in the brain that produce dopamine. Dopamine is a neurotransmitter or chemical messenger that sends signals between nerve cells and is essential for muscle movement.
Levodopa is the first-line treatment in Parkinson’s disease. It relieves motor symptoms as it is converted into dopamine, a process that increases dopamine levels in the brain.
However, as the disease progresses, patients’ response to levodopa decreases. This often leads to off-episodes, in which patients experience flares of symptoms between doses of levodopa.
Tasmar is a catechol-O-methyltransferase (COMT) inhibitor. COMT is an enzyme that breaks down levodopa before it reaches the brain, making it less effective. By blocking the COMT enzyme, Tasmar maintains levodopa levels in the blood. This results in a continuous stimulation of brain cells that leads to an increase in levodopa’s effectiveness.
Tasmar in clinical trials for Parkinson’s
Tasmar was initially investigated in two 13-week studies and one six-week study that involved a total of 594 patients. These studies compared Tasmar with a placebo when added to patients’ medication regimens. The main goal was to measure the time patients spent “on” — when levodopa is working well and symptoms are controlled — or in an off-state. Results showed Tasmar was more effective than the placebo in reducing the severity of symptoms. The therapy decreased off time by 20 to 30%.
Another study enrolled 150 Parkinson’s patients who were being treated with levodopa and entacapone, another COMT inhibitor. That study compared continuing to take entacapone or switching to Tasmar. Its main objective was to see how many patients could increase their on-time by at least one hour by switching to Tasmar.
The results revealed that more patients responded to Tasmar (53%) than to entacapone (43%).
Tasmar is available as oral tablets containing 100 mg of tolcapone. The therapy must be used in combination with carbidopa and levodopa. It is usually taken three times a day, with the first dose taken with carbidopa and levodopa. The second dose of Tasmar should be taken six hours later, and the third dose 12 hours later.
It may cause liver damage, so regular blood tests are required to monitor liver function. These should be done every two to four weeks in the first six months of treatment and then as deemed necessary by the physician.
For this reason, Tasmar is contraindicated, or not recommended for use, in patients with liver disease, or in those who have had liver damage caused by Tasmar.
People who have shown allergic reactions to Tasmar or to one of its ingredients should also not take the treatment. Tasmar also is contraindicated in patients with a history of nontraumatic muscle injury, high fevers, and confusion caused by some medications.
Getting off Tasmar can lead to withdrawal symptoms, so it should not be stopped suddenly.
Common side effects include abdominal pain, diarrhea, nausea, and dizziness. Patients also may also feel somnolence, or daytime sleepiness, and fall asleep during daily activities. Other frequent side effects include fever, hallucinations, and headache.
Additional information may be found on Tasmar’s label.
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