Indicated in the treatment of Parkinson's disease, post-encephalitic parkinsonism, and symptomatic parkinsonism that may follow carbon monoxide intoxication or manganese intoxication. Carbidopa allows patients treated for Parkinson's disease to use much lower doses of levodopa.
Levodopa, the metabolic precursor of dopamine, crosses the blood-brain barrier and is converted to dopamine in the brain. Carbidopa is a dopa decarboxylase (DDC) inhibitor which reduces the peripheral metabolism of Levodopa to dopamine, and thus, more Levodopa becomes available to the brain.
ORAL As monotherapy in Parkinson’s disease: Adult: Per tab contains L-dopa 100 mg & carbidopa 25 mg. Initially, 1 tab tid. Increase by 1 tab/day every 1-2 days up to a max. of 8 tabs of any strength! day. If the patient has been taking L-dopa alone, the combination should be started after a gap of at least 8 hr after stopping L-dopa.
Caution should be exercised when the following drugs are administered concomitantly with Levodopa-Carbidopa prolonged-release tablet.
Antihypertensive agents: Symptomatic postural hypotension has occurred when levodopa/decarboxylase inhibitor combinations were added to the treatment of patients receiving some antihypertensive drugs. Therefore when therapy with Levodopa-Carbidopa prolonged-release tablet is started, dosage adjustment of the antihypertensive drug may be required.
Antidepressants: There have been rare reports of adverse reactions, including hypertension and dyskinesia, resulting from the concomitant use of tricyclic antidepressants and carbidopa-levodopa preparations.
Anticholinergics: Anticholinergics may affect the absorption and thus the patient’s response.
Iron: Studies demonstrate a decrease in the bioavailability of carbidopa and/or levodopa when it is ingested with ferrous sulphate or ferrous gluconate.
Other drugs: Dopamine D2 receptor antagonists (e.g. phenothiazines, butyrophenones and risperidone) and isoniazid may reduce the therapeutic effects of levodopa. The beneficial effects of levodopa in Parkinson’s disease have been reported to be reversed by phenytoin and papaverine. Patients taking these drugs with Levodopa-Carbidopa prolonged-release tablet should be observed carefully for loss of therapeutic response. Concomitant therapy with selegiline and carbidopa-levodopa may be associated with severe orthostatic hypotension not attributable to carbidopa-levodopa alone. Since levodopa competes with certain amino acids, the absorption of levodopa may be impaired in some patients on a high protein diet. The effect of simultaneous administration of antacids with Levodopa-Carbidopa prolonged-release tablet on the bioavailability of levodopa has not been studied.
Lactation, narrow angle glaucoma. melanoma, psychosis, severely decompensated endocrine. Heart disease, liver disease, dementia, psychosis, pregnancy, elderly, heart disease. Regular monitoring of renal & hepatic function is reccomended.
Nausea, vomiting, anorexia, increased risk of GI bleeding in peptic ulcer patients. Orthostatic hypotension, cardiac arrhythmias. Psychiatric symptoms (depression w/ or w/o suicidal tendency). Abnormal involuntary movements or dyskinesias, delirium, hallucinations (elderly). Slight elevation of liver enzymes, leucopenia & thrombocytopen ia. Severe postural hypotension in elderly.
There are no controlled data in human pregnancy. Two reports have described three patients who received levodopa or levodopa-carbidopa throughout pregnancy without evidence of fetal harm. Levodopa should only be given in human pregnancy when benefit outweighs risk. This drug in relatively low doses was used without apparent harmful effects in the nursing infant by 1 mother with Parkinson's disease; limited data indicate this drug is poorly excreted into breast milk.
Store in a cool and dry place, protected from light.
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