PREPARATIONS: Tablets (carbidopa/levodopa): 10/100, 25/100 mg. Tablets (Controlled Release): 25/100 and 50/200 mg.
DRUG INTERACTIONS: The use of the following drugs with carbidopa-levodopa can enhance the anti-Parkinson's effects of levodopa:
- amantadine (Symmetrel),
- benztropine (Cogentin),
- procyclidine (Kemadrin), or
- trihexyphenidyl (Artane)
The following drugs can inhibit dopamine in the brain and shouldn't be used in combination with levodopa:
- haloperidol (Haldol),
- loxapine (Loxitane),
- metoclopramide (Reglan),
- phenothiazines such as prochlorperazine (Thorazine); and
- thioxanthenes as thiothixene (Navane).
These drugs, therefore, can worsen Parkinson's disease and reverse the beneficial effects of levodopa. Methyldopa (Aldomet) and reserpine also can interfere with the beneficial actions of carbidopa-levodopa and can increase the risk of side effects.
The occurrence of postural hypotension (reduced blood pressure when standing from a sitting or lying down position) may increase when carbidopa-levodopa is combined with drugs that reduce blood pressure. Phenytoin (Dilantin) can increase the break-down of carbidopa-levodopa, reducing its effectiveness. Use of carbidopa-levodopa with monoamine oxidase inhibitors (MAOI's) antidepressants, for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), and procarbazine (Matulane), can result in severe and dangerous elevations in blood pressure. MAOI's should be stopped 2-4 weeks before starting carbidopa-levodopa therapy.
Quick GuideParkinson's Disease: Symptoms, Causes, Stages, and Treatment
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