Sinemet - Carbidopa

Levodopa + carbidopa (Sinemet) Carbidopa inhibits peripheral metabolism of levodopa to dopamine and reduces required dosage and toxicity. Carbidopa does not enter CNS. 

Levodopa is a chemical formulation found in plants and animals that is converted into dopamine by nerve cells in the brain. Levodopa does cross die blood-brain barrier, and a small amount is dien converted to dopamine. This allows the drug to have a pharmacologic effect in patients witii Parkinson s disease (Pig. 29-1). Combining levodopa witii another drug (carbidopa) causes more levodopa to reach die brain. When more levodopa is available, the dosage of levodopa may be reduced. Carbidopa has no effect when given alone. Sinemet is a combination of carbidopa and levodopa and is available in several combinations (eg, Sinemet 10/100 has 10 mg of carbidopa and 100 mg of levodopa Sinemet CR is a time-released version of die combined drugs). 

Sinemet (Merck Sharp Dohme)-comb. with carbidopa Larodopa (Roche) Madopar (Roche)-comb. with benserazide Sinemet (Du Pont)-comb. with carbidopa Doparl (Kyowa)... 

Sinemet (Du Pont)-comb. with carbidopa generic... 

Levodopa/Carbidopa (Sinemet ) Standard, immediate-release LD Sinemet CR Start with 1 tab (1 00 mg LD, 25 mg CD) two or three times daily ... 

Carbidopa therefore inhibits the conversion of L-dopa to dopamine in the peripheral tissues and the blood while leaving it unchanged in the brain. The combination of L-dopa and carbidopa is marketed as Sinemet and was the treatment of choice for parkinsonism for many years. Note the structural similarity between carbidopa and L-dopa. Carbidopa looks enough like L-dopa to occupy the L-dopa site on the decarboxylase. At the same time, the subtle structural differences render carbidopa indifferent to the enzyme. It is an inhibitor, not a substrate. 

Dopamine-Boosting Medications. Levodopa/carbidopa (Sinemet), bromocriptine (Parlodel), pramipexole (Mirapex), and ropinirole (Requip) increase dopamine nenrotransmission in the brain by one or another mechanism. These medications do not reliably induce sleep, and in some patients are activating. They are certainly not true sedative-hypnotics. They are most often used by neurologists to treat Parkinson s disease. 

Sinemet 10/100 Sinemet 25/100 Sinemet 25 0 Antiparkinsonian Tab Carbidopa 10 mg, levodopa 100 mg Tab Carbidopa 25 mg, levodopa 100 mg Tab Carbidopa 25 mg, levodopa 250 mg 1 tab tid-qid dyskinesia, nausea, mental status changes, paranoia, psychosis, depression. 

Benztropine (Cogentin) Bromocriptine (Parlodel) Carbidopa/Levodopa (Parcopa, Sinemet)... 

If levodopa is administered alone, it is extensively metabolized by L-aromatic amino acid decarboxylase in the liver, kidney, and gastrointestinal tract. To prevent this peripheral metabolism, levodopa is coadministered with carbidopa (Sinemet), a peripheral decarboxylase inhibitor. The combination of levodopa with carbidopa lowers the necessary dose of levodopa and reduces peripheral side effects associated with its administration. 

Tablets [Atamet, Sinemet)-. 10 mg carbidopa/100 mg levodopa, 25 mg carbidopa/100 mg levodopa, 25 mg carbidopa/250 mg levodopa. 

Oral sustained-release (Sinemet CR) 25 mg carbidopa and 100 mg levodopa 50 mg carbidopa and 200 mg levodopa Carbidopa/levodopa/entacapone (Stalevo)... 

Levodopa-carbidopa is also available in a con-trolled-release preparation (Sinemet CR) that is absorbed more slowly and is intended to provide prolonged effects.48 The use of this controlled-release preparation may be helpful in patients who respond well to levodopa initially but experience dyskinesias... 

The etiology of progressive death of dopaminergic neurons in substantia nigra of Parkinson s disease brains remains unclear. Dopamine deficiency in Parkinson s disease is commonly treated with L-dopa and carbidopa, a periphera dopa decarboxylase inhibitor (Sinemet). Since its introduction, L-dopa has been shown to be effective in treating Parkinson s disease. However, high concentrations of L-dopa produce side effects such as psychosis, on-off effects, abnormal involuntary movements, and akinetic crisis. 

Carbidopa is often coadministered with L-dopa to reduce the amount of l-dopa converted to dopamine in the periphery. Carbidopa thereby increases l-dopa s effectiveness and reduces its associated side effects, including nausea, vomiting, and loss of appetite. This compound blocks the action of the enzyme dopa-decarboxylase, which converts L-dopa into dopamine. Controlled-release Sinemet is a combination of L-dopa and carbidopa, with an extended half-life of immediate-acting combination products, producing an increased duration of effect. A combination of immediate-acting and controlled-release L-dopa and carbidopa is often used. In a number of patients, administration of the controlled-release pill only results in an insufficient conversion of central dopamine (93). The most common side effects associated with the administration of l-... 

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