Sinemet

Sinemet is a brand-name medication that combines levodopa and carbidopa in a fixed-dose tablet. It is used to treat the motor symptoms of Parkinson's disease and other conditions characterized by low dopamine levels, typically when symptoms are not adequately controlled with other therapies.

Levodopa is a precursor to dopamine that can cross the blood–brain barrier, where it is converted to dopamine and helps restore dopaminergic signaling. Carbidopa is a peripheral decarboxylase inhibitor that prevents much of the levodopa from being broken down outside the brain, increasing brain availability of levodopa and reducing peripheral side effects such as nausea and vomiting.

Sinemet is available in immediate-release and extended-release formulations (Sinemet CR). Dosing is individualized and usually started at a low level with gradual increases to balance symptom control and the risk of dyskinesias. Typical daily levodopa doses vary widely, often ranging from several hundred milligrams to about 1000 mg or more, divided across multiple doses; some patients may require higher totals depending on response and tolerance.

Common adverse effects include nausea, dizziness, orthostatic hypotension, dyskinesias, confusion, and psychosis. Urine or sweat may darken with treatment. The medication can interact with certain drugs, notably non-selective MAO inhibitors, and with vitamins such as pyridoxine (vitamin B6), which can affect levodopa's effectiveness in the absence of carbidopa.

Sinemet is generally considered first-line symptomatic therapy for Parkinson's disease in many patients, particularly as the disease advances or fluctuations in response occur. See also Parkinson's disease, levodopa, and carbidopa.