SINEMET SUMMARY
TABLETS
SINEMET®
(CARBIDOPA-LEVODOPA)
SINEMET* (Carbidopa-Levodopa) is a combination of carbidopa and levodopa for the treatment of Parkinson's disease and syndrome.
SINEMET is indicated in the treatment of the symptoms of idiopathic Parkinson's disease (paralysis agitans), post-encephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication and/or manganese intoxication. SINEMET is indicated in these conditions to permit the administration of lower doses of levodopa with reduced nausea and vomiting, with more rapid dosage titration, with a somewhat smoother response, and with supplemental pyridoxine (vitamin B6).
In some patients a somewhat smoother antiparkinsonian effect results from therapy with SINEMET than with levodopa. However, patients with markedly irregular ("on-off") responses to levodopa have not been shown to benefit from SINEMET.
Although the administration of carbidopa permits control of parkinsonism and Parkinson's disease with much lower doses of levodopa, there is no conclusive evidence at present that this is beneficial other than in reducing nausea and vomiting, permitting more rapid titration, and providing a somewhat smoother response to levodopa.
Certain patients who responded poorly to levodopa have improved when SINEMET was substituted. This is most likely due to decreased peripheral decarboxylation of levodopa which results from administration of carbidopa rather than to a primary effect of carbidopa on the nervous system. Carbidopa has not been shown to enhance the intrinsic efficacy of levodopa in parkinsonian syndromes.
In considering whether to give SINEMET to patients already on levodopa who have nausea and/or vomiting, the practitioner should be aware that, while many patients may be expected to improve, some do not. Since one cannot predict which patients are likely to improve, this can only be determined by a trial of therapy. It should be further noted that in controlled trials comparing SINEMET with levodopa, about half of the patients with nausea and/or vomiting on levodopa improved spontaneously despite being retained on the same dose of levodopa during the controlled portion of the trial.
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