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Indications And Usage Carbidopa Tablets Are Indicated For Use With Carbidopa-Levodopa Or With Levodopa In The Treatment Of The Symptoms Of Idiopathic Parkinson's Disease (paralysis Agitans), Postencephalitic Parkinsonism, And Symptomatic Parkinsonism Which May Follow Injury To The Nervous System By Carbon Monoxide Intoxication And/or Manganese Intoxication. Carbidopa Is For Use With Carbidopa-Levodopa In Patients For Whom The Dosage Of Carbidopa-Levodopa Provides Less Than Adequate Daily Dosage (usually 70 Mg Daily) Of Carbidopa. Carbidopa Is For Use With Levodopa In The Occasional Patient Whose Dosage Requirement Of Carbidopa And Levodopa Necessitates Separate Titration Of Each Medication. Carbidopa Is Used With Carbidopa-Levodopa Or With Levodopa To Permit The Administration Of Lower Doses Of Levodopa With Reduced Nausea And Vomiting, More Rapid Dosage Titration, And With A Somewhat Smoother Response. However, Patients With Markedly Irregular ("on-Off") Responses To Levodopa Have Not Been Shown To Benefit From The Addition Of Carbidopa. Since Carbidopa Prevents The Reversal Of Levodopa Effects Caused By Pyridoxine, Supplemental Pyridoxine (vitamin B 6 ), Can Be Given To Patients When They Are Receiving Carbidopa And Levodopa Concomitantly Or As Carbidopa-Levodopa. 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 Alone Have Improved When Carbidopa And Levodopa Were Given Concurrently. This Was Most Likely Due To Decreased Peripheral Decarboxylation Of Levodopa Rather Than To A Primary Effect Of Carbidopa On The Peripheral Nervous System. Carbidopa Has Not Been Shown To Enhance The Intrinsic Efficacy Of Levodopa. In Deciding Whether To Give Carbidopa With Carbidopa-Levodopa Or With Levodopa To Patients Who Have Nausea And/or Vomiting, The Physician Should Be Aware That, While Many Patients May Be Expected To Improve, Some May 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 Carbidopa And Levodopa With Levodopa Alone, About Half The Patients With Nausea And/or Vomiting On Levodopa Alone Improved Spontaneously Despite Being Retained On The Same Dose Of Levodopa During The Controlled Portion Of The Trial.
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